1. 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

2. 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

3. 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

4. 2- Bulk powders for external use
Examples:
- Douche powders
- Dentifrice powders
- Triturates
- Insufflations
- Dusting powders

5. B- Divided powders
Definition: Pharmaceutical powders dispensed as divided doses
Examples:
- Packets
- Cachets
- Powders for injection

6. 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

7. 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.

8. 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.

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

10. 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

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

12. 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.

13. 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.

14. 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.

15. 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.

16. Official powdered Drugs
A- Official powdered vegetable drugs
B- Official powdered drugs
Check the USP, BP and SFDA

17. 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

18. 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.

19. Mixers for Powders Tumbling Mixers/Blenders
Barrel blender V-shape blender

20. Tumbling Blenders
Cube blender Double cone blender

21. Tumbling Blenders

22. 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.

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

24. 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.

25. 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.

26. 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.