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CONTENT MODULE 1.

June 13, 2024

MODULE 1. GENERAL CONCEPTS OF DRUG TECHNOLOGY. POWDERS. LIQUID DOSAGE FORMS.

CONTENT MODULE 1. GENERAL CONCEPTS OF DRUG TECHNOLOGY. POWDERS.

LESSON 2. POWDERS WITH SUBSTANCES WITH DIFFERENT PHYSICAL AND CHEMICAL PROPERTIES.

POWDERS WITH SUBSTANCES WITH DIFFERENT PHYSICAL AND CHEMICAL PROPERTIES.

Properties of Powders

The word “powder” refers to a chemical or mixture that is solid in physical state. In compounding, “powder” refers to a dosage formulation that is solid in physical state. But the formulation may be composed of only the active drug or may be a mixture of the active drug and other ingredients.

Powders offer some unique advantages:

· each dose can contain a different amount of active drug

· can be administered easily to infants and young children who cannot swallow tablets or capsules

· drug will have a rapid onset of action since disintegration is not required

· can be applied to many body cavities such as ears, nose, tooth socket, throat

· drugs tend to most stable as a solid

· can be made into many different dosage formulations (capsules, tablets, powders for reconstitution, dusting powders, bulk powders, powders for inhalation, etc.)

Pharmaceutical powders are formulated to be exist as fine particles. The powders are then smooth to the touch and nonirritating to the skin. Powders generally range from 0.1 to 10 micron in size. The size of the particles are often expressed as a number which corresponds to the mesh screen size of a sieve. The screen size indicates the number of openings in the mesh screen per inch. For example, a # 40 sieve has 40 openings per inch in the screen mesh. Particles that can sift through that mesh are said to be “40 mesh” size.

Below is a list of mesh sizes and the size of the mesh opening in millimeters (1/1000 of a meter) or microns (1/1,000,000) of a meter. Of coarse there is a correlation between the size of the mesh opening and the particle size of the sifted powder. As the opening becomes smaller, so will be resulting particle size. Most of the particles of a sifted powder will have approximately the size as the mesh opening.

Mesh Opening Size

Mesh Size Number

millimeters

microns

9.52

9520

4.76

4760

2.38

2380

2.00

2000

0.84

840

0.59

590

0.42

420

0.297

297

0.250

250

0.210

210

0.177

177

100

0.149

149

120

0.125

125

200

0.074

View a video demonstration on how to sieve a powder

The USP 24/NF19 uses descriptive terms to define powder fineness. The table below shows the correlation their classification.

Description Term

Mesh Opening Size (microns)

Mesh Size Number

Very Coarse

> 1000

2 – 10

Coarse

355 -1000

20 – 40

Moderately Coarse

180 – 355

40 – 80

Fine

125 – 180

80 – 120

Very Fine

90 – 125

120 – 200

A good powder formulation has an uniform particle size distribution. If the particle size distribution is not uniform, the powder can segregate according to the different particle sizes which may result in inaccurate dosing or inconsistent performance. A uniform particle size distribution insures an uniform dissolution rate if the powder is to dissolve, an uniform sedimentation rate if the powder is used in a suspension, and minimizes stratification when powders are stored or transported.

Reducing the particle size of a powder will result in an uniform distribution of particle sizes. The process of reducing the particle size is called comminution. In extemporaneous compounding, there are three methods of comminution:

· Trituration is the continuous rubbing or grinding of the powder in a mortar with a pestle. This method is used when working with hard, fracturable powders.

· Pulverization by Intervention is used with hard crystalline powders that do not crush or triturate easily, or gummy-type substances. The first step is to use an “intervening” solvent (such as alcohol or acetone) that will dissolve the compound. The dissolved powder is then mixed in a mortar or spread on an ointment slab to enhance the evaporation of the solvent. As the solvent evaporates, the powder will recrystallize out of solution as fine particles.

· Levigation reduces the particle size by triturating it in a mortar or spatulating it on an ointment slab or pad with a small amount of a liquid in which the solid is not soluble. The solvent should be somewhat viscous such as mineral oil or glycerin. This method is also used to reduce the particle size of insoluble materials when compounding ointments and suspensions.

Classification of Powders

Bulk Powders

Bulk powders are nonpotent and can be dosed with acceptable accuracy and safety using measuring devices such as the teaspoon, cup, or insufflator. This practically limits the use of orally administered bulk powders to antacids, dietary supplements, laxatives, and a few analgesics. Many bulk powders are used topically.

Dusting Powders

Dusting powders are fine medicinal (bulk) powders intended to be dusted on the skin by means of sifter-top containers. A single medicinal agent may be used as a dusting powder; however, a base is frequently used to apply a medicinal agent and to protect the skin from irritation and friction. Bentonite, kaolin, kieselguhr, magnesium carbonate, starch, and talc are used as inert bases for dusting powders. Powder bases absorb secretions and exert a drying effect, which relieves congestion and imparts a cooling sensation. All extemporaneous dusting powders should be passed through a 100-200 mesh sieve to ensure that they are grit free and will not further mechanically irritate traumatized areas.

Douche Powders

Douche powders are used to prepare solutions that cleanse the vagina. Most douche powders are used for their hygienic effects, but a few contain antibiotics.

Douche powders are prescribed as a matter of convenience for the patient, since a powder is more portable than a bulky solution. The formula is developed so that a teaspoonful or tablespoonful of powder dissolved in a specified volume of water provides the desired concentration. The pH usually ranges from 3.5 to 5 when the solution is prepared. Feminine bulb syringes or fountain syringes are used for vaginal irrigation. Since many of the ingredients are volatile (e.g., menthol, thymol, and volatile oils), douche powders should be packaged in glass jars with a wide mouth. Some commercial douche powders are available in metal foil packets, which contain the proper amount of powder for a single douche. Many douches are also available as prepared unit of use solutions in disposable applicators.

Insufflations

Insufflations are extremely fine powders to be introduced into body cavities. To administer an insufflation, the powder is placed in the insufflator, and when the bulb is squeezed, the air current carries the fine particles through the nozzle to the region for which the medication is intended. All extemporaneously compounded insufflations must be passed through a 100 mesh sieve. Pressurized packages provide an elegant approach to the administration of insufflations.

Powder Sprays

In contrast to dusting powders, powders dispensed under pressure will deliver targeted and uniform application at the desired site. Also, in an aerosol container medicated powders may be maintained in a sterile condition. The powder particles must be a definite size range to prevent clogging of the valve orifice and to provide uniformity of application. In general, powders that are to be packaged as powder sprays must not contain particles greater than 50 microns if they are to be sprayed successfully.

POWDERS are solid medicinal forms for internal and external application consisting of one or some medicinal substances and having a loose property

Powders

• Powders are dry mixtures of finely divided medicinal and non-medicinal agents intended for internal or external use.

• Powders may be dispensed to a patient and used in

1. bulk form (such as powders measured by the spoonful to make a douche solution);

2. divided into single dosage units and packaged in folded palters or unit of use envelopes.

¡ Powders

¡ A Pharmaceutical powder is a mixture of finely divided drugs or chemicals in a dry form meant for internal or external use.

¡ Advantages of powders :

¡ 1-flexibility of compounding.

¡ 2-Good chemical stability

¡ 3-Rapid dispersion of ingredients (because of small particle size

¡ Disadvantage of powders:

1-Time-consuming preparation

2-Inaccuracy of dose( size of measuring spoon, density of powder, humidity, degree of settling , fluffiness.

3-Unsuitability for many unpleasant tasting, hygroscopic and deliquescent drugs

¡ Mixing of powders

Large-Scale Mixing Equipment

The ideal mixer should

1- produce a complete blend rapidly to avoid product damage.

2- It should be cleaned and discharged easily

3- be dust-tight

4 require low maintenance and low power consumption.

¡ Small-Scale Mixing Equipment

1- Mortar and pestle

* The pharmacist most generally employs the mortar and pestle for the small-scale mixing

* The mortar and pestle method is a single operation. Thus, it is particularly useful where some degree of particle-size reduction as well as mixing is required as in the case of mixtures of crystalline material.

Morters are prepared usually from Wedgwood ware, porcelain or glass.

A- Glass mortars:

* Are designed primarily for use in preparing solutions and suspensions of chemical materials in a liquid. Also are suitable for Preparing ointments

* Glass has advantage of being comparatively nonporous and of not staining easily and thus is particularly useful when-substances such as flavoring oils or highly colored substances are used. Glass cannot be used for comminuting hard solids.

¡ B- Wedgwood mortars

Are suited for comminution of crystalline solids.

* Wedgwood is relatively porous and will stain quite easily. A Wedgwood mortar is available with a roughened interior which aids in the comminution process but requires care in washing since particles of the drugs may be trapped in the rough surface and cause contamination.

¡ C- Porcelain mortars

are very similar to Wedgwood, except that the exterior surface of the former is usually glazed and thus less porous.

¡ Pestles

* Are made of the same material as the mortar.

* Pestles made entirely of porcelain are objectionable, because they are broken easily. Pestles and mortars should not be interchanged.

* The efficiency of the grinding or mixing operation depends largely on a maximum contact between the surfaces of the head of the pestle and the interior of the mortar

¡ Small-Scale Mixing Equipment

2- Spatulation

The blending of powders with a spatula on a tile or paper used sometimes for small quantities or when the mortar and pestle technique is undesirable.

It is not suitable for large quantities of powders or for powders containing one or more potent substance because homogenous blending may

not occur.

¡ Small-Scale Mixing Equipment

3- Sieving

Sieving usually is employed as a pre-or

post-mixing method to reduce loosely held

agglomerates and to increase the overall

effectiveness of blending process.

¡ Extemporaneous Techniques

1. Use of geometric dilution for the incorporation of small amounts of potent drugs

2. Reduction of particle size of all ingredients to the same range.

3. Sieving wheecessary to achieve mixing or reduction of agglomerates, especially in powders into which liquids have been incorporated.

4. Heavy trituration, when applicable, to reduce the bulkiness of a powder.

5. Protection against humidity, air oxidation and loss of volatile ingredients.

Powders are prepared most commonly either as:

1- Divided powders and bulk powders which are mixed with water prior to administration

2- Dusting powders which are applied locally.

3- Dentifrices

4- Insufflations

¡ Extemporaneous Techniques( cont. )

The manually operated procedures are trituration, pulverization by intervention and levigation.

1- Trituration: is used to comminute( reduce particle size) & to mix powders.

1-A porcelin preferred than glass morter.

2- A glass morter is preferrable for chemicals that stain a porcelin. When granular or crystalline materials are to be incorporated in to powdered product ,these materials are comminuted individually and then blended together in the morter.

2- Pulverization by Intervention

Substance are reduced& subdivided with an additional material ( i.e solvent) that can be removed easily after pulverization is complete.

* This technique is applied to

Substances which are gummy and tend to reagglomerate or which resist grinding. As camphor which is gummy, so addition of alcohol or other volatile solvent can be reduced readily to a fine powder.

Similarly, iodine crystals may be comminuted with the aid of ether.

In both instances the solvent is permitted to evaporate and the powdered material is recovered

¡ 3- Levigation

In this process

A- paste is first formed by the addition of a suitable non solvent to the solid material.

B-Particle-size reduction then accomplished by rubbing the paste in a mortar with a pestle or on an ointment’ slab using a spatula.

¡ Divided Powders

Are dispensed in the form of

individual doses and generally are

dispensed in papers, properly folded

(chartulae). They also may be

dispensed in metal foil, small heat-

sealed plastic bags or other

containers.

¡ Divided Powders

– After weighing, comminuting and mixing

the ingredients, the powders must be

divided accurately into the prescribed

number of doses. In order to achieve

accuracy consistent with the other steps in

the preparation, each dose should

be weighed individually and transferred to a

powder paper. Following completion of this

step the powder papers are folded.

¡ Powder Papers

– Four basic types of powder papers are available.

1. Vegetable parchment, a thin semi-opaque moisture-resistant paper.

2. White bond, an opaque paper with no moisture-resistant properties.

3. Glassine, a glazed, transparent moisture-resistant paper.

4. Waxed, a transparent waterproof paper.

¡ Powder Papers

Hygroscopic and volatile drugs can be protected best by using a waxed paper, double-wrapped with a bond paper to improve the appearance of the completed powder.

Parchment and glassine papers offer limited protection for these drugs.

¡ Special Problems

1-Volatile Substances – The loss by volatilization may be prevented or retarded by use of heat-sealed plastic bags or by double wrapping with a waxed or glassine paper inside of a bond paper.

¡ Special Problems

2-Eutectic Mixtures

Liquids result from the combination of phenol, camphor, menthol, thymol, antipyrine, phenacetin, acetanilid, aspirin, salol and related compounds at ordinary temperatures.

These so-called eutectic mixtures may be incorporated into powders by addition of an inert diluent.

Magnesium carbonate or light magnesium oxide are used commonly and effective diluents for this purpose, although kaolin, starch, bentonite and other absorbents have been recommended.

¡ Special Problems( cont )

3-Liquids – In small amounts, liquids may be incorporated into divided powders.

Magnesium carbonate, starch or lactose may be added to Increase the absorbability of the powders if necessary.

When the liquid is a solvent for a nonvolatile heat-stable compound, it may be evaporated gently on a water bath. Lactose may be added during the course of the evaporation to increase the rate of solvent loss by increasing the surface area.

¡ Special Problems( cont )

4-Hygroscopic and Deliquescent Substances – Substances that become moist because of affinity for moisture in the air may be prepared as divided powders by adding inert diluents. Double-wrapping is desirable for further protection. Extremely deliquescent compounds cannot be prepared satisfactorily as powders.

¡ Bulk Powders

may be classified as oral powders, dentifrices, douche powders, dusting powders, insuffiations and triturations.

Oral Powders – These generally are supplied as finely divided powders or effervescent granules.The finely divided powders are intended to be suspended or dissolved in water or mixed with soft foods, e.g, applesauce, prior to administration.

Antacids and laxative powders frequently are administered in this form

¡ Effervescent granules

* Contain sodium bicarbonate and either citric acid, tartaric acid or sodium biphosphate in addition to the active ingredients.

* On solution in water, carbon dioxide is released as a result of the acid-base reaction. The effervescence from the release of the carbon dioxide serves to mask the taste of salty or bitter medications.

* The completed product must be dispensed in tightly closed glass containers to protect it against the humidity of the air.

¡ Effervescent powders

– Other preparative techniques have been reported for effervescent powders such as a fluidized-bed procedure in which the powders are blended and then suspended in a stream of air in a Wurster chamber. Water is sprayed into the chamber resulting in a slight reaction and an expansion of the particles to form granules ranging in size from 10- to 30-mesh.

¡ Effervescent powders

¡ This approach apparently offers a number of advantages over the older techniques. The extent of reaction and particle size are controlled during the manufacture. A drying oven, trays and even grinding devices are not required. Furthermore, the technique lends itself to a continuous as well as a batch operation.

¡ Dentifrices

¡ These may be prepared in the form of a bulk powder, generally containing a soap or detergent, mild abrasive and an anticariogenic agent.

¡ Douche Powders

¡ These products are completely soluble and are intended to be dissolved in water prior to use as antiseptics or cleansing agents for a body cavity.

¡ They most commonly are intended for vaginal use, although they may be formulated for nasal, otic or ophthalmic use. Generally, since aromatic oils are included in these powders.

¡ Dispensing in wide-mouth glass jars serves to protect against loss of volatile materials and permits easy access by the patient

¡ Dusting Powders

– These are locally applied nontoxic preparations that are intended to have no systemic action.

– They always should be dispensed in a very fine state to enhance effectiveness and minimize irritation.

– Extemporaneously prepared should be dispensed in sifter-top packages. Commercial powders are available in sifter-top containers or pressure aerosols. The latter, more expensive than the other containers, offer the advantage of protection from air, moisture and contamination, as well as convenience of application.

–

¡ Dusting Powders

¡ Dusting powders are applied to various parts of the body as lubricants, protectives, absorbents, antiseptics, antipruritics, anti bromhidrosis agents, astringents and antiperspirants.

¡ Insufflations

– These are finely divided powders introduced into body cavities such as the ears, nose, throat, tooth sockets and vagina. An insufflator (powder blower) usually is employed to administer these products.

¡ Insufflations

¡ However, the difficulty in obtaining a uniform dose has restricted their general use.

¡ Specialized equipment has been developed for the administration of micronized powders of relatively potent drugs. The Norisodrine Sulfate Aerohaler Cartridge (Abbott) is an example.

In the use of this Aerohaler, inhalation by the patient causes a small ball to strike a cartridge containing the drug. The force of the ball shakes the proper amount of the powder free, permitting its inhalation. Another device, the Spin haler turbo-inhaler (Fisons), is a propeller-driven device designed to deposit a mixture of lactose and micronized cromolyn sodium into the lung as an aid in the management of bronchial asthma.

– These are dilutions of potent powdered drugs, prepared by intimately mixing them with a suitable diluent in a definite proportion by weight. They were at one time official as 1 to 10 dilutions.

¡ The pharmacist sometimes prepares triturations of poisonous substances, eg, atropine, in a convenient concentration using lactose as the diluent, for use at the prescription counter.

The correct procedure for preparing such triturations or any similar dilution of a potent powder medicament, to insure uniform distribution of the latter, is:

1- Reduce the drug to a moderately fine powder in a mortar.

2-Add about an amount of diluents & mix well by thorough trituration in the mortar.

3-Successively add portions of diluent ,triturating after each addition ,until the entire quantity of diluent has been incorporated. Under no circomostances should the entire quantity of of diluent be added at once to the drug that is to be diluted, ununiform dispersion will be achieved

Advantages of Powders

 When it is not possible to dispense a drug as a solution or a suspension, because of its insolubility or because it is susceptible to microbial continuation if it is wetted, then it is a good idea to dispense it as a powder. A Few decades ago, when crude vegetable drugs were the most often prescribed drugs, dispensing them as powders was a good option.

 When a bulky drug that has a large dose is to be administered, a powder is a good way of administering it. Several compound bulk powders used to be there and mostly these were given for stomach conditions, such as indigestion, constipation and diarrhea. They used to contain large amounts of light materials such as Magnesium Carbonate. You can see the prescription of Gregory’s powder, as an example for this, in the last part of this article where prescriptions are discussed. When we are using powders for this type of use, we give the instruction “take a teaspoonful of the powder and swallow with water”. We can easily see that this is not an accurate way of administering medicines, as the same weights of various medicaments often have different volumes. So, potent substances should never be given in the form of bulk powders.

 When tablets and capsules were not known administering insoluble, potent substances as powders was an option.

 Small children and old people cannot swallow tablets and capsules. In such situations powders are a good option.

 Powders dispense fast in the Gastro Intestinal tract and the drugs are absorbed faster from these. Whereas tablets have to disintegrate first, the capsule shell has to dissolve first and then there may be some problems because excipients are included in these.

 When the patient has to mix the ingredients before administration, dispensing in separate divided powders is a convenient way.

 Powders are very good from chemical stability point of view.

Disadvantages of Powders

 They are time consuming to prepare and pack.

 They are bulky to carry about.

 Powders may spill when they are being opened.

 When a tablet or a capsule is not suitable, a well formulated suspension may be a suitable alternative.

 When a medicament with an unpleasant taste has to be administered, it may be given as a suspension or in a hard capsule form.

 Powders are not an ideal way of dispensing substances that are volatile deliquescent, hygroscopic or oxygen-sensitive.

CLASSIFICATION AND prescription METHODS OF POWDERS.

Depending on compound powders divided into

simple consisting of one ingredients(Pulveres simplices)

complex consisting of some substances (Pulveres compositi)

Depending on quantity of doses powders divided on

powders with separate doses (Pulveres divisi)

undivided powders (Pulveres indivisi)

Depending on a method of application powders are divided into two groups:

powders for internal use

powders for external use

METHODS OF POWDER prescribing :

1. Distributive – the prescription indicates the amount of a substance per one dose and amount of doses, which are necessary to prepare (this method is the most frequently used).

Rp.: Dibazoli 0.01

Papaverini hydrochloridi 0.02

Sacchari 0.25

Misce, fiat pulvis

Da tales doses N 10

Signa. 1 powder 3 times per day.

2. Separating – the prescription indicates of a medicinal substance for all powders at once and the quantity of doses, which are necessary to divide the total mass

Rp.: Dibazoli 0.1

Papaverini hydrochloridi 0.2

Sacchari 2.5

Misce, fiat pulvis

Divide in partes aequales N 10

Signa. 1 powder 3 times per day.

The first method of prescribing is more convenient for checking doses of the substances from lists A and B.

The MAIN TECHNOLOGICAL PROCEDURES

of POWDER’S PREPARING

The technological process of preparing of medicines in a chemist’s consists of separate stages and operations, which should be carried out in the appropriate sanitarian conditions.

The main requirements for powders:

1.A loose property and optimum degree of a finess of all components of a complex powder (dispersibility).

2. Proportional distribution of substances in the total mass of a complex powder (homogeneity).

3. Correct dosing and stability of substances during storage.

4. For some powders – sterility (dusting powders on wounds, for newborns).

THE MAIN STAGES OF POWDER PREPARATING:

1. Weighing, powdering and sifting of medicinal substances.

2. Blending of components (for complex powders).

3. Dosing on a mass, packing of doses and quality control of powders 4. Powder registration for dispensing.

The necessity of fulfilment of all technological stages during preparation of powders depends on:

 amount of prescribed medicinal substances and their physical and chemical properties;

 density, volumetric or bulk mass, degree of fineness, spraying or dyeing ability, hygroscopicity of prescription formula substances, medical purpose of a powder.

According to these factors, various requirements exist concerning the degree of a fineness, method of preparation, packing and dispensing of powders.

In all variety of formulas of complex powders 2 cases may be distinguished:

 The 1-st case – when the medications of a complex powder are prescribed in equal or approximately equal amounts

 The 2-nd case – when the medications of a complex powder prescribed in extremely different amounts

In the first case, when medicinal substances are prescribed in equal amounts and their physical and chemical properties are the same, the order of blending has not significant, they are mixed in order of prescribing, as a rule.

If the amounts of prescribed substances are the same, but their physical and chemical properties differ, there are following rules of blending:

1. The substance without activity should be powdered first.

2. If there is no substance without activity in the formula, at first the substance having the least percent of rubbing in pores of a mortar is triturated. Frequently the value of powder’s losses is explained by electrization of mortar’s wales and a powder (different charges). Therefore, it is important to foresee the value of losses correctly for solving the problem of ingredients’ trituration in a clean mortar because the losses while triturating a substance in a clean mortar are rather great.

3. At first the coarse-crystalline substances should be powdered, then fine-crystalline ones and, at last, amorphous ones.

4. The heavy substances should be added in the mortar first, then –lighter substances are added. The easily spraying substances added last.

Let’s consider the example when the medicinal substances of a complex powder are prescribed in equal amounts:

Rp.: Magnesii oxydi

Bismuthi subnitratis ana 0.25

Misce, fiat pulvis

Da tales doses N 12

Signa. 1 powder 3 times per day.

The given medicine is a complex dosed powder for internal use, which includes 2 substances in its composition prescribed in equal amounts, but they are different by their density, bulk mass, spraying as well as by the trituration in pores of a mortar.

By the density bismuth subnitrate is more heavy than magnesium oxide (4.9g/sm³ against 3.65). If we look at the table describing volumetric or bulk mass, the mass for magnesium oxide is 0.387, therefore it will be sprayed, and the mass for bismuthi subnitrate is 1.735. Thus, what substance should be powdered first? The substance with bigger bulk mass and which is not sprayed. However,basic bismuth subnitrate penetrates deeper in the mortar’s pores (42 mg), than magnesium oxide (16 mg). Therefore, it is better by a portion of magnesium oxide to rub pores of the mortar, then add bismuth subnitrate in the mortar, and at last remaining quantity of magnesium and mix carefully.

When the medicinal substances of a complex powder are prescribed in different amounts, the main rules of blending are:

1. Start powdering in the mortar with medicinal substances without therapeutical activity, and if there is not such a substance in the formula, the preparation should begin from a component prescribed in greater quantity and which is less lost in the mortar’s pores (taking into account the crystalline structure and spraying ability of a substance).

2. After that it is nesessary to start powdering and blending of medicinal substances with a component prescribed in the smallest amount ( in the mortar where the substance without activity previously added).

Then add the remaining components gradually, taking into account their amounts. The procedure of blending from the smallest component to the biggest one must be the same.

The homogeneity of a powder mixture is reached when components are prescribed in the ratio from 1:1 (for poisonous and strong-effective substances) to 1:5 (for substances of the general list).

When the ratio is increased more than 1:5, the homogeneity of a mixture is greatly disturbed.

POWDERS WITH DYEING SUBSTANCES.

Medicinal substances which have colour can be divided into 2 groups:

 Dyeing substances: acriquin, methylene dark blue, diamond green, riboflavine, etacridine lactate, furaciline, potassium permanganate etc;

 Coloured substances: dermatol, quinosol, protargol etc

Dyeing medicinal substances, as well as their solutions, mixtures leaving a coloured trace on containers, parking materials, equipment and other subjects belong to the 1-st group. This trace is impossible to wash out by usual sanitary and technical processing. They are stored in a separate cabinet on the wale of laboratory, where there are also separate manual balances for weighing of these substances.

Coloured medicinal substances do not leave the coloured trace on containers, packing materials. They are stored as usual and the powders with such medicinal substances are prepared according to the general rules.

During the preparation of powders with dyeing substances, it is necessary to take into account that dyeing substances can make the mortar, pestle and working place dirty.

1. Therefore, for preparation of powders with dyeing substances it is necessary: To have a separate working place or to work on the assistant table covered with a sheet of paper, which should be displaced and burnt after work.

2. At first, it is necessary to place substance without any colour, then add dyeing substance and, at last, add the second colourless substance.If the colourless substances are prescribed in different quantities, mix them and then divide into two parts and dyeing substances should be between two layers of colorless substances.

After work, the mortar and pestle should be washed out immediately.

POWDERS WITH POORLY POWDERED MEDICINAL SUBSTANCES

There are several poorly powdered substances such as: camphora, menthol, thymole, phenylsalisilate, iodine, boric acid, streptocide etc. Their fineness is improved in the presence of an auxiliary liquid with rendering effect.

While powdering in a dry form the substances such as camphora, menthol, thymol, iodine cling together, adhere to the walls of the mortar and pestle. For these substances add the liquid calculated on 10-15 drops for each 1.0 g of the substance. It is necessary to add the same quantity of alcohol for phenylsalicylate, which has solid crystals.

For some medicinal substances, such as boric acid, streptocide, sodium tetraborate the amount of liquid is decreased twice: 5 drops of alcohol or 8 drops of ether for 1.0 g of the substance powdered. The remaining components of a complex powder are added without complete evaporation of the alcohol.

The volatile liquids are used also for grinding of dusting substances, which irritate the mucous membranes (salicylic acid), for extremely poisonous substances (arsenic anhydride, mercury dichloride, etc).Furthermore some of poorly powdered substances are also highly volatile, odours ones (such as camphora, menthol, thymol). Aromatic medicinal substances should be stored in a separate cabinet, which is caled « Aromatic and dyeing substances ») from other substances in the closed containers, impenetrable for odour. While working with them they should be weighed on the separate balances. The blending of such medicinal substances is carried out according to the general rules for preparating powders, but it is necessary to add them in the last queue.

For example:

Rp.: Camphorae 0,1

Sacchari 0,25

Misce, fiat pulvis

Da tales doses N10.

Signa. 1 powder 3 times a day.

The given medication is a complex dosed powder for internal use, with aromatic, volatile, poorly powdered substance -camphora.

Procedure: at first triturate 2.5 g of sugar and put it completely on the capsule. 1 g camphora is triturate with 10 drops of 95 % alcohol in the mortar, then, not waiting the evaporation of the alcohol, add remaining amount of powdered sugar. Weigh out 0. 35 g and pack in the parchment capsules. The waxed capsules are not recommended, because camphora with paraffin and wax form eutectic mixtures.

Pharmaceutical Powders in a WORLD

Powders were very popular dosage forms, once upon a time; at a time when it was common practice for a pharmacist to “compound” a prescription and dispense it. Today compounding is not thee and “oral powders” are almost non existent. Only you see occasionally, when old people or children cannot swallow tablets or capsules; the tablets or capsules are made into powders, by the people who are administering these medicines to them. Powders can be swallowed more easily but their taste is also felt more by the tongue. Let us today look at what are powders what are their advantages and disadvantages and let us consider a few prescriptions for powders. I want to just explain to you that the principles which are valid in the preparation of powders at a compounding level are also equally valid in the ‘“manufacture”’ of powders or which are ultimately becoming granules in the preparation of tablets.

Classification of Powders

Bulk Powders for internal use

Bulk Powders for external use

Divided (single dose) powders

Advantages of Powders

When it is not possible to dispense a drug as a solution or a suspension, because of its insolubility or because it is susceptible to microbial continuation if it is wetted, then it is a good idea to dispense it as a powder. A Few decades ago, when crude vegetable drugs were the most often prescribed drugs, dispensing them as powders was a good option.

When a bulky drug that has a large dose is to be administered, a powder is a good way of administering it. Several compound bulk powders used to be there and mostly these were given for stomach conditions, such as indigestion, constipation and diarrhea. They used to contain large amounts of light materials such as Magnesium Carbonate. You can see the prescription of Gregory’s powder, as an example for this, in the last part of this article where prescriptions are discussed ( 2.1 ). When we are using powders for this type of use, we give the instruction “take a teaspoonful of the powder and swallow with water”. We can easily see that this is not an accurate way of administering medicines, as the same weights of various medicaments often have different volumes. So, potent substances should never be given in the form of bulk powders.

When tablets and capsules were not known administering insoluble, potent substances as powders was an option. You can see the prescriptions on codeine phosphate and Hyoscine hydrobromide as examples for this principle in (2.5 &2. 6).

Small children and old people cannot swallow tablets and capsules. In such situations powders are a good option.

Powders dispense fast in the Gastro Intestinal tract and the drugs are absorbed faster from these. Whereas tablets have to disintegrate first, the capsule shell has to dissolve first and then there may be some problems because excipients are included in these.

When the patient has to mix the ingredients before administration, dispensing in separate divided powders is a convenient way. See the prescription on effervescent granules in (2.13).

Powders are very good from chemical stability point of view.

Disadvantages of Powders

They are time consuming to prepare and pack.

They are bulky to carry about.

Powders may spill when they are being opened.

When a tablet or a capsule is not suitable, a well formulated suspension may be a suitable alternative.

When a medicament with an unpleasant taste has to be administered, it may be given as a suspension or in a hard capsule form.

Powders are not an ideal way of dispensing substances that are volatile deliquescent, hygroscopic or oxygen-sensitive.

A pharmaceutical powder is a mixture of finely divided drugs and / or excipients in dry form, meant for internal or external use.

One of the following three methods was widely used by the pharmacist, in yester years, for the preparation of powders.

Methods of Preparation

Trituration: Trituration is a method by which we make coarse powders into small particles by rubbing them in a mortar with a pestle. We also use trituration to mix two dry powders.

Pulverization by Intervention: When it is difficult to powder a material in a mortar because it is soft or gummy, we add a second material which helps in the powdering and which is latter removed. So when material A resists grinding, we add we can then grind them or pulverize them easily. Them material B is removed. For example, powdering camphor is difficult, so we add a small amount of alcohol to it and we them powder it, then we allow alcohol to evaporate.

Levigation: The substance is powdered by adding a suitable non solvent (levigations agent) to it, to form a paste. We then rub the paste in a mortar and pestle. Liquid Paraffin is a commonly used levigations agent. This method is used to incorporate solids into dermatologic or ophthalmic ointments and suspensions to prevent a gritty feel.

Principles involved

There are four principles involved in the preparations of powders. These principles are true for yester year’s powders and they are true for the preparation of granules in today’s manufacture of tablets and capsules.

Drug Content Uniformity : When we are mixing powdered drugs, the final objective is to produce such a powder which is having drug content uniformity throughout. If the finished powder is taken in a paper, any 100mg sample, taken from any corner or middle or any place in it of the drugs should have the same ratio or the same contents of the drugs involved in the prescription.

Fine size : The size of the powder should be fine. Coarse powders are difficult to swallow.

Free flowing : The powders should not be wet. They should not be in lumps.

Good taste : Unpleasant taste should not be there. If it is there, it should be masked by adding sweetness.

Amount should not be too large or too small.

Dispensing Procedure

These points are achieved by preparing powders in the following way.

Geometric dilution : In this method we first take into the mortar, that drug which is minimum in weight (say drug A, 500mg) we powder it with the pestle, then we add to the mortar, the drug which is next higher in weight (say drug B, 1g); we add into the mortar that much of the second material which is approximately equal to the material in the mortar (500mg). We mix them and then we add the remaining quantity of B and mix them. Them we add the remaining drugs in order of increasing weights (say drug C, 2g; drug D 3g etc.). Each time we add an amount that is equal to the amount in the mortar. When we take the materials into the mortar in this way and mix them, we get very good mixing.

Weighing : After the material of the powder is prepared it is divided into individual doses. In weighing certain points are to be kept in mind. Today nobody is working in the imperial system; but if you are working in the imperial system 1 grain is the minimum that can be weighed and 2 grains are the minimum that can be dispensed. In the metric system, by convention 100mg is the minimum that can be weighed and 200mg is the minimum that can be dispensed. If the final weight of a divided powder in coming out to be, say 750mg, we take it to the nearest 100, that is 800mg, by adding an inert diluent such as lactose to it. The final weight of a divided powder or bulk powder is not allowed to be in a fraction or a part of 100mg.

Packing : The packing of powders in done in a very systematic and specific manner. Packs which are known as pharmacists packs are prepared by folding a neatly cut rectangular paper two times, each time keeping an edge. Then the final pack has a central portion and two flaps. After placing the powder in the center of the pack, the flaps are closed such that one flap goes into the other.

Dispensing : An envelope is taken and is neatly labeled. Below a sample label is given.

Labeling particulars change with each prescription. When writing labels one should be very careful, no errors should be committed, because the patient follows the labeling instructions.

After neatly labeling the envelope the powders should be kept in the envelope and the envelope should be neatly sealed and dispensed.

Different varieties of Powders

Bulk Powders for internal use

When prescriptions contain large amounts of light drug substances they fall into this category. We prepare a bulk powder, pack the whole powder into one pack and send it with the instruction that for every dose, the patient should take one teaspoonful of the Gregory’s powder NP whose formula is given below. Formula :

Heavy Magnesium Carbonate – 325 g

Light Magnesium Carbonate – 325 g

Rhubarb, in powder – 250 g

Ginger, in powder – 100 g

———

1000 g

———

The Principle and the procedure are given in the last section where 15 prescriptions are discussed.

Bulk powders for external use

Dusting powders

Medical : They are used for superficial skin conditions, they should not be used for application to open wounds or application or broken skin. The label should clearly specify this point. We need not sterilise the ingredients of these powders but we must be sure that they are not containing pathogens.

Surgical : These powders must be sterile because they are used in body cavities and are applied on wounds. They are sprayed on burnt areas and are placed on the umbilical cords of infants. These powders usually contain an antibacterial agent. The diluent is sterilizable maize starch, which is also called as absorbable dusting powder.

Insufflations

These are fine powders which are used to produce either a local effect, such as in the treatment of ear or nose or throat infections or a systemic effect, such as when they are inhaled into the lungs and get absorbed from the lungs. If a drug is destroyed in the GIT, when it is taken orally, then making it into an insufflation is a good option.

In fact this formulation is coming back into wide use now, with the difference being that it is being manufactured in pharmaceutical companies with the aid of the latest technologies. Making a drug into a fine powder, packing it into containers called inhalers, seeing that the powder goes and lodges in the lungs and then releases the drug there involves a lot of technology. But if that can be managed, it is a good dosage form, because absorption of drug from the lungs is very fast, the lungs are highly perfused and the area offered for absorption is equal to the area of a tennis court!

The diluent usually used for insufflation is lactose. For preparations meant for open wounds the diluent used is sterilisable maize starch.

Divided Powders

Each dose of the powder is separately packed into a packet. The number of packets in the envelope is the number of packets ordered by the doctor. We usually proceed for 2 or 3 powders more than the number ordered by the doctor, because some material may be wasted in triturations and weighing. If all the materials or drugs present in a powder are white in color, we usually add a drop of amaranth alcoholic solution to the powder and go on mixing it. The end point of the mixing would be the even spreading of the deep pink color of amaranth. If the final weight of the divided powder is less than 200mg, we add enough lactose as diluent to the whole mixture; such that the weight of individual powder comes to 200mg. If liquids have to be made into free flowing powders, we add enough lactose to absorb the liquid on to it. We add enough lactose such that, when the final powder is divided into doses, each dose is more than 200mg and is also rounded to the nearesh 100mg.

If a powder contains a potent medicine such as in the case of codeine phosphate or Hyoscine hydrobromide we dilute them with lactose to bring them up to enough weight such that they can be dispensed.

If a powder contains a hygroscopic drug, the final powder is double wrapped.

If a powder contains materials that form a eutectic mixture the eutectic formation is allowed, and is absorbed onto a diluent the final powder is sent in a double wrapped condition.

If a powder contains an effervescent mixture, the acid and the alkaline salt are separately packed and dispensed with suitable directions.

Aspirin Powder

Rx Aspirin – gr v

Mitte tales decim

Signa : Unam Somni nocte sumenda

Translation:

Aspirin – 300 mg

Send 10 powders.

label: Take one at night.

Weight of one powder is 300 mg.

Principle : Single ingredient is there. So there is no need for any mixing. If the powder is coarse, it should be made into a fine powder.

Procedure : Take the drug into a mortar and make it into a fine powder. Weigh out 300mg into each of 10 packets. Neatly label the envelope, keep the packs in the envelope and dispense.

Prescription No 2

Sodium bicarbonate – 300mg

Activated Charcoal – 60mg

Prepare powders and send six powders.

Label : Take one powder after meals.

Weight of one powder is 360 mg.

Principle : The two ingredients should be thoroughly mixed until the black colour of charcoal is uniformly distributed.

Procedure : Calculate for 8 powders. Take 480mg of activated charcoal into a mortar. Add approximately equal amount of sodium bicarbonate to it and mix thoroughly. Then add the remaining amount of sodium bicarbonate and mix thoroughly. Weigh out 360mg of the final powder into each of 6 packets. Put the packets in a neatly labeled envelope and dispense.

Prescription No 3

Phenacetini – gr iv

Caffinae – gr i

Fiat pulvis Mitte tales Decem

Signetur : Capiat unum dolore urgente

Translation:

Phenacetin – 240 mg

Caffeine — 60 mg

Prepare a powder. Send 10 powders.

Label: Take one when pain is severe.

Weight of one powder is 300 mg.

Principle :

Minimum weight that can be weighed is 100mg.

Minimum weight that can be dispensed is 200mg.

When both the ingredients are white in colour add a drop of amaranth, alcoholic solution to impart colour to the preparation.

Procedure :

Calculate for 12 doses.

Take Caffeine 120mg into the mortar, powder it and add an approximately equal amount of Phenacetin and mix. Then add the remaining amount of Phenacetin and mix.

Add a drop of alcoholic solution of amaranth and go on mixing until the colour is uniformly spread.

Weigh out 300mg into each of ten packets and dispense in a neatly labelled envelope.

Prescription No 4

Aspirin – 5gr

Citric Acid – ½gr

Calcium Carbonate – 1½gr

Label : The Powders

Dissolve in water and take wheecessary.

Send 12 powders.

Translation:

Aspirin – 300mg

Citric Acid – 30mg

Calcium Carbonate – 90mg

Label: The Powders

Dissolve in water and take wheecessary.

Send 12 powders.

Calculations:

For 14 powders:

Aspirin — 4200mg

Citric Acid — 420 mg

Calcium Carbonate —– 1260 mg

Lactose — 1120 mg

Weight of one powder is 500 mg.

Principle : Because citric acid is hygroscopic iature the final powder should be double wrapped.

Procedure :

Calculate for 14 powders.

Add lactose to bring the final weight of each powder to 500mg

Take 420mg of Citric Acid into mortar, add an equal amount of calcium carbonate and mix; then add the remaining amount of calcium carbonate and mix; then gradually add the lactose and the aspirin and thoroughly mix.

Weigh 500mg into each of 12 packets, double wrap and dispense in a neatly labeled envelope.

Double wrapping involves, spreading an inside layer of wax paper in each packet.

Prescription No 5

Codeine Phos – gr 1/6

Fiat Pulvis : Mitte tales decem.

Signa : Unus omni nocte sumendus.

Translation:

Codeine Phosphate – 10mg

Prepare a powder. Send 10 such powders.

Label : Take one every night.

Calculations in Imperial System:

For 12 powders.

Codeine phosphate – 2gr = 120mg

Lactose (2×12) – 2gr – 22gr = 1320mg

Calculations in Metric System:

For 12 powders:

Codeine Phosphate—120 mg

Lactose — 2280 mg

Weight of one powder is 200 mg.

Principle: Codeine phosphate is a potent medicine and is prescribed in a small amount. It should be diluted with enough lactose to bring it up to sufficient weight, i.e. 200 mg.

Procedure: Both are fine powders. Take codeine phosphate in the mortar, and triturate, adding the lactose in progressively increasing portions. Weigh out 200 mg into each of 10 packets and dispense in a neatly labeled envelope.

Prescription No 6

Hyoscinae Hydrobromidi – gr 1/150

Fiat pulvis : Mitte duodecim.

Signa : Capiat Unum bis in die

Translation:

Hyoscine hydrobromide — 0.4mg

Prepare a powder. Send 12 powders

Label : Take one twice a day.

Calculations in Imperial System:

Calculations for 15 powders : 15 powders should weigh 30 grains.

Take 1gr (60mg) of Hyoscine hydrobromide and thoroughly mix with 9gr of lactose.

1gr of this mixture(I) contains 1/10 th grain of Hyoscine hydrobromide.

Take 1gr of I and mix with 29gr of lactose. After thorough mixture, 1gr of this

contains 1/10*1/30=1/300th gr of Hyoscine hydrobromide and 2gr contain (1/300)*2=1/150th

grain of Hyoscine hydrobromide.

Weight of one powder is 120 mg.

Calculations in Metric System:

100mg is the minimum that can be weighed and 200mg is the minimum to be

dispensend.

Take 100mg of hyoscine hydrobromide and mix with 900mg of lactose (I).

(b) 100mg of I contains 10mg of Hyoscine hydrobromide; mix 100mg of I with

4,900mg of lactose.

Now 500mg contain 10mg

? contain 0.4mg

5000×0.4 = 200mg

Weight of one powder is 200 mg.

Principle: Hyoscine hydrobromide is a very potent substance. It should be double diluted for dispensing.

Procedure:

As per the calculations above , take 100 mg of Hyoscine hydrobromide and mix with 900 mg of lactose. This is mixture I.

Take 100 mg of mixture I and mix with 4900 mg of Lactose. This is mixture II.

Weigh out 200 mg of mixture II into 12 packs.

Put the packs in a neatly labeled envelope and dispense.

Prescription No 7

Creosote – m ss

Lactose – q.s

Mitte tales six.

Signa : Unum nocte sumendum.

Translation:

Creosote – = 0.03ml

Lactose – enough

Send six powders.

Label : Take one at night.

Weight of each powder is determined by weighing the final powder after mixing Creosote with Lactose.

Principle: Creosote is a liquid. The doctor wants it to be given as a powder. So it should to be incorporated into a solid like Lactose.

Procedure:

Proceed for 8 powders 8×0.03 = 0.24ml

Take 0.24ml of creosote into a small amount of lactose in a glass mortar.

Triturate, adding lactose until a free flowing powder is obtained (All the liquid must be incorporated in it.)

Transfer onto a piece of butter paper and find the weight of the powder.

Divide the weight by 8 to get the weight of a single powder. Weigh out six such powders, double wrap and dispense in a neatly labeled envelope.

Prescription No 8

Send zi of boric acid containing 1% w/w iodine (8% w/v of alcoholic iodine solution is provided). Label : Apply on the affected part.

Calculations:

Boric Acid – 4g

100 grams of the bulk powder should contain 1 gram of iodine.

g should contain

8g of iodine is contained in 100ml

0.04g iodine is contained ?

Weight of the bulk powder ( single packet) is 4 g.

Principle: Alcoholic solution of Iodine should be incorporated into Boric acid.

Procedure:

Take Boric Acid into a glass mortar( because Iodine forms a stain on a porcelein mortar which cannot be removed easily), add 0.5ml of the alcoholic solution of iodine to it, and triturate till there is a dry powder. All the alcohol should evaporate, till then trituration should be done.

Double wrap and dispense as a single packet.

Prescription No 9

Rx.

Sodii Bicarbonatis – gr x

Rhei Pulverati – gr iii

Olei Menthae Piperitae – mss

Fiat pulvis : Mitte novem.

Signentur : Unus e cyatho vinoso aquae post cibos quoties opus sit capiendus.

Translation:

Sodium Bicarbonate – 600 mg

Powdered rhubarb — 180 mg

Oil of Peppermint — 0.03 ml

Prepare a powder. Send 9 powders.

Label: When necessary, take daily, one, with a wine glass of water after meals.

Principle:

The prescribed amounts yield a powder weighing between 13 and 14 grains, hence adjustment to 14grains with lactose will be suitable.

The formula for 10 powders will be

Sodium Bicarbonate – 100gr

Powdered Rhubarb – 30gr

Oil of Peppermint – 5 minims

Lactose – to 140gr

In Metric System: For 10 powders

Sodium bicarbonate – 6000 mg

Powdered Rhubarb — 1800 mg

Oil of Peppermint — 0.3 ml

Lactose —- to 8000 mg

Powdered Rhubarb is a plant material. Plant materials are often supplied as coarse materials. Rhubarb powder should be finely powdered before it is included in the prescription.

Procedure: After admixture of the first three ingredients, transfer the whole of the material to a scale, add lactose to produce 8000 mg , return to the glass mortar and mix thoroughly, double wrap and dispense as divided powders in a neatly labeled envelope..

Prescription No 10

Zinc Oxide – z ss

Calamine – gr xx

Starch – z i

Fiat pulvis subtitis : Mitte z i

Signa : Pulvis conspensus.

Apply three times a day.

Translation:

Zinc oxide – 2 g

Calamine — 1200 mg

Starch — up to 32 g

Prepare a fine powder. Send 4 g.

Label: The Dusting Powder.

Apply three times a day.

Principle:

This is a dusting Powder. So there should not be any coarse or gritty particles. It should be triturated into a fine powder.

Procedure:

Take the ingredients into a mortar , finely powder them, mix them thoroughly and dispense as a single packet in a neatly labeled envelope.

Prescription No 11

Salicylic Acid – 0.05g

Benzoic Acid – 0.06g

Camphor – 0.01g

Menthol – 0.02g

Phenol – 0.01g

Starch – 1g

Mix and send 10g.

Signa : Sprinkle between toes.

Principle:

Camphor, menthol and phenol are separately solids at room temperature. But if any two of these three are mixed in a mortar they will form a liquid, this is known as eutectic formation.

Procedure: This problem of eutectic formation is overcome like this: Take the three eutectic forming liquids into a mortar and mix; eutectic formation will be there; now incorporate this liquid in the starch, add the other ingredients and mix thoroughly. Double wrap and dispense as a single bulk powder in a neatly labelled envelope.

Prescription No 12

Benzoic Acid – 1g

Zinc Oxide – z ss

Mix : Label : Dusting powder

Signa : To be applied to face and neck frequently.

Principle: This is a bulk powder containing two white powders; a drop of amaranth solution should be added to the powder to ascertain thorough mixing.

Procedure: Take the ingredients into a mortar , add a drop of amaranth solution and mix thoroughly. Dispense as a bulk powder in a single pack in a neatly labeled envelope.

Prescription No 13

Sodium Potassium tartarate – 7.5grams

Sodium bicarbonate – 7.5grams

Tartaric Acid – 25g

Supply in two packets.

Signa : Dissolve powder (i) in a glass of water and then add powder (ii), stir and take

the liquid while effervescing.

Priciple: Sodium bicarbonate reacts with tartaric acid and gives off effervescense.

Procedure: Sodium potassium tartarate and sodium bicarbonate should be kept in one pack. Tartaric Acid should be kept in a second pack. Both of them should be kept in an envelope and dispensed with proper directions on the label.

Prescription No 14

Heavy Magnesium Carbonate – 325mg

Light Magnesium Carbonate – 325mg

Rhubarb powder – 250mg

Sugar – 100mg

Mix. Take 1 teaspoonful of powder at night.

Principle: Large doses of light substances are prescribed in this prescription. So the ingredients are taken in geometric dilution method and mixed thoroughly. Powder Rhubarb thoroughly if it is coarse.

1- Properties of powders :

Powders offer some unique advantages:

· each dose can contain a different amount of active drug

· can be administered easily to infants and young children who cannot swallow tablets or capsules

· drug will have a rapid onset of action since disintegration is not required

· can be applied to many body cavities such as ears, nose, tooth socket, throat

· drugs tend to most stable as a solid

· can be made into many different dosage formulations (capsules, tablets, powders for reconstitution, dusting powders, bulk powders, powders for inhalation, etc.)

Mesh Opening Size

Mesh Size Number

millimeters

microns

9.52

9520

4.76

4760

2.38

2380

2.00

2000

0.84

840

0.59

590

0.42

420

0.297

297

0.250

250

0.210

210

0.177

177

100

0.149

149

120

0.125

125

200

0.074

The USP 24/NF19 uses descriptive terms to define powder fineness. The table below shows the correlation their classification

Description Term

Mesh Opening Size (microns)

Mesh Size Number

Very Coarse

> 1000

2 – 10

Coarse

355 -1000

20 – 40

Moderately Coarse

180 – 355

40 – 80

Fine

125 – 180

80 – 120

Very Fine

90 – 125

120 – 200

· Trituration is the continuous rubbing or grinding of the powder in a mortar with a pestle. This method is used when working with hard, fracturable powders.

2- Classification of powders:

Bulk Powders:

Douche Powders:

Douche powders are used to prepare solutions that cleanse the vagina. Most douche powders are used for their hygienic effects, but a few contain antibiotics.Douche powders are prescribed as a matter of convenience for the patient, since a powder is more portable than a bulky solution. The formula is developed so that a teaspoonful or tablespoonful of powder dissolved in a specified volume of water provides the desired concentration. The pH usually ranges from 3.5 to 5 when the solution is prepared. Feminine bulb syringes or fountain syringes are used for vaginal irrigation. Since many of the ingredients are volatile (e.g., menthol, thymol, and volatile oils), douche powders should be packaged in glass jars with a wide mouth. Some commercial douche powders are available in metal foil packets, which contain the proper amount of powder for a single douche. Many douches are also available as prepared unit of use solutions in disposable applicators.

Insufflations:

Powder Sprays:

4Preparation of divided powder

Divided powders or charts are single doses of powdered medicinals individually wrapped in cellophane, metallic foil, or paper. The divided powder is a more accurate dosage form than bulk powder because the patient is not involved in measurement of the dose. Cellophane and foil-enclosed powders are better protected from the external environment until the time of administration than paper-enclosed powders. Divided powders are commercially available in foil, cellophane or paper packs.

All drugs are reduced to a fine state of subdivision before weighing , the weighed powders are blended by geometric dilution or mixing in ascending order of amount.