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 Form Bulk and Divided A – 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 Powders may 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 should be 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: Ensure an even distribution of the active component(s) Ensure an even appearance of the DF Ensure that the DF releases the drug at the correct site and at the desired rate Mechanisms of Mixing: 1.Diffusion:Movement of single particles 2.Convection:Movement of groups of particles 3.Shear :Sliding of particles in planes over each other

Mixing of powders The ideal mixer should 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.

Mixers for Powders Tumbling Mixers/Blenders Barrel 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. The addition of baffles or rotating bars will also cause convective mixing, for example the V‑mixer with agitator bar. Presence of significant difference in particle size, as segregation is likely to occur.

Extemporaneous Methods 1- Spatulation 2- Trituration 3-Levigation Mixing of Powders Extemporaneous Methods 1- Spatulation 2- Trituration 3-Levigation

Small-Scale Mixing Equipment 1- 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.

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.