Pharmaceutical powders are mixtures of dry, finely divided drugs and chemicals that can be used internally or externally. Powders have advantages like masking unpleasant tastes, being more stable than liquids, and allowing rapid drug effect. However, powders are also difficult to protect from decomposition and require more preparation effort than other dosage forms. There are two main types of powders: divided powders packaged in individual doses, and bulk powders for dusting or mixing. Effervescent powders contain acids and bases that react when mixed with water, masking bitter tastes and promoting gastric secretions.