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

Powders As a Dosage FormBulk and DividedA – Bulk Powders

Definition: Pharmaceutical powders dispensed as a whole in one container

Types: 1- Oral powders:Examples: Antacid powder

Oral antibiotic powder

2 -Bulk powders for external use•Examples:

• -Douche powders• -Dentifrice powders

• -Triturates• -Insufflations

• -Dusting powders

B- Divided powders

Definition: Pharmaceutical powders dispensed as divided doses

Examples: - Packets - Cachets

- Powders for injection

Bulk Powdersmay be classified as oral powders, dentifrices, douche powders, dusting powders, insufflations 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 .

•

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

•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 Aero haler

Cartridge (Abbott) is an example .

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 shouldbe weighed individually and transferred to a powder paper. Following completion of this step the powder papers are folded.

Official powdered Drugs

A- Official powdered vegetable drugs

B- Official powdered drugs

Check the USP, BP and SFDA

Mixing

Importance:1. Ensure an even distribution of the active

component(s)2. Ensure an even appearance of the DF3. Ensure that the DF releases the drug at the correct

site and at the desired rate

Mechanisms of Mixing:1.Diffusion:Movement of single particles2.Convection:Movement of groups of particles3.Shear :Sliding of particles in planes over each other

Mixing of powders

Large-Scale Mixing Equipment

The ideal mixer should1 -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 .

Mixers for Powders

Tumbling Mixers/BlendersBarrel blender V-shape

blender

Tumbling Blenders

• Cube blender Double cone blender

Tumbling Blenders

Factors affecting mixing efficiency by tumbling mixers

1. Too high a rotation speed will cause the material to be held on the mixer walls by centrifugal force, and too low a speed will generate insufficient bed expansion and little shear mixing.

2. The addition of baffles or rotating bars will also cause convective mixing, for example the V‑mixer with agitator bar.

3. Presence of significant difference in particle size, as segregation is likely to occur.

Mixing of Powders

Extemporaneous Methods

1 -Spatulation2 -Trituration3-Levigation

Small-Scale Mixing Equipment

1 -SpatulationThe 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 .

2 -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 .

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 .