9. POWDERS AND GRANULES

Powders and Granules

Powders:

Pharmaceutical powders are mixtures of finely divided drugs and/or chemicals in dry form, available in crystalline or amorphous states. Particle size affects the dissolution, absorption, and therapeutic efficacy.

Advantages of Powders:

One of the oldest dosage forms, used internally and externally.
More stable compared to liquid dosage forms.
Allows convenient dosing according to patient needs.
Less chance of incompatibility than liquids.
Rapid onset of action due to fine particle size and quick dissolution.
Large quantities can be orally administered by mixing in liquids.
Suitable for patients who cannot swallow tablets or capsules (children, elderly).
Economical and easy to carry.

Disadvantages of Powders:

Bitter or unpleasant tasting drugs are unsuitable for powders.
Deliquescent and hygroscopic drugs cannot be dispensed as powders.
Sensitive to atmospheric conditions.
Small quantities (<100 mg) are difficult to weigh accurately.
Dispensing powders is time-consuming.

Classification of Powders:

Bulk powders for internal use
Bulk powders for external use
Simple and compound powders for internal use
Powders enclosed in cachets and capsules
Compressed powders (tablets)

SIMPLE AND COMPOUND POWDERS:

Simple powders contain a single ingredient; compound powders contain two or more combined ingredients. Both are divided into individual doses wrapped in paper.

Example of simple powder: Dispense six powders of Aspirin 300 mg each.

Example of compound powder: Dispense eight powders of A.P.C. (Aspirin 300 mg, Paracetamol 150 mg, Caffeine 50 mg).

Insufflations:

Medicated dusting powders for body cavities (nose, throat, ears, vagina) administered via insufflators. Challenges include uniform dosing and blockage when wetted. Modern pressure aerosols improve dose control and protect products.

Dusting Powders:

For external skin application; should be finely subdivided (pass through sieve no. 80). Two types: medical (superficial skin) and surgical (wounds, burns). Sterilization is important. Common bases include talc and kaolin. Applied with containers, puffs, or gauze. Generally safe but inhalation by infants may cause inflammation.

Eutectic and Explosive Powders:

Eutectic mixtures liquefy when components with lower melting points combine; handled by separate powder dosing or absorbent mixing. Explosive powders (oxidizers + reducers) require separate preparation and cautious handling.

Dentifrices (Tooth Powders):

Bulk powders for teeth cleaning containing soap/detergent, mild abrasives (calcium carbonate, sodium chloride), and anticaries agents. Used with toothbrushes.

Example formula: Hard soap 5 g, precipitated calcium carbonate 94 g, saccharine sodium 2 g, peppermint oil 4 g for 100 g tooth powder.

Granules:

Granules are dry aggregates of powder particles (usually 2-4 mm diameter) prepared for better flow, reduced dust, and ease of administration. They are commonly used for oral medications requiring large doses or unstable in solutions. Granules may include flavoring, sweetening, and granulating agents and are dried and packed for patient use.

Effervescent Granules:

Contain medicament mixed with citric acid, tartaric acid, and sodium bicarbonate. When dissolved in water, produce carbon dioxide, mask bitter tastes, and aid gastric absorption. Preparation includes heat and wet methods with careful drying and packaging.