POWDERS According to the British Pharmacopoiea, powders are defined as sub-divided solid particles classified according to their particle sizes which ranges between 1.25um – 1.7mm.
Powders can also be defined as dry mixture of finely divided solids containing medicinal and non-medicinal agents for internal and external use.
Pharmaceutically, powders can be defined as solid dosage forms in which the ingredient (additives) are in a state of divided particles.
ADVANTAGES OF POWDERS Powders are more stable than liquid preparations
It is convenient to disperse drugs with large doses
The rate of dissolution is faster compared to tablets and capsules.
Powders dispersed in water can easily be swallowed by children and old people.
Powders have flexibility in compounding i.e. it is easy to prepare powders.
DISADVANTAGES OF POWDERS They are not convenient for the patient to carry about.
Inaccuracy of measurement of dose in bulk powders.
It is difficult to mask unpleasant taste.
Powder is not suitable for volatile drugs that can cause irritation in the GIT and also not suitable for drugs that can be inactivated in the stomach.
COARSE POWDERS: These are powders in which all the particles pass through a sieve nominal mesh aparture of 1.7mm but not more than 40% will pass through a sieve with a nominal mesh aparture of 355um.
MODERATELY COARSE POWDERS:These are powders in which all the particles pass through a sieve with nominal mesh aparture of 710um but not more than 40% should pass through a sieve with nominal mesh aparture of 250um
FINE POWDERS: All the particles should pass through a sieve of nominal aparture of 180um but not more than 40% should pass through a sieve with nominal mesh aparture of of 125um.