When a capsule or tablet is swallowed, it enters liquids; the process that breaks it down into particles is called disintegration. Dissolution happens when a solid is dissolved in gastrointestinal fluids, and a medicine's dissolution rate determines its bioavailability, or usability, via absorption into the bloodstream, says Oluwatoyin A. Odeku for Pharmainfo.net.
A medicine's solubility, or ability to be dissolved in liquid, determines its dissolution rate, but some medicines are designed to be soluble without partial or complete disintegration, according to Odeku. In addition to solubility, a medicine must be able to pass through the barrier of the intestines to be bioavailable. Thus, both the degree of solubility and the degree of permeability affect a capsule or tablet's dissolution rate, notes Khadka et al. in an article in the Asian Journal of Pharmaceutical Sciences.
Because poor solubility lowers dissolution rate, and therefore decreases bioavailability, methods have been developed to make solid medicines more soluble. Reducing solids to powder form by grinding, mixing and pounding has been practiced by chemists and pharmacists since the early beginnings of their science. More advanced methods of powder technology reduce solids to even finer powders through particle size reduction and other particle technologies. Some of these techniques include freeze-drying, ball and jet milling and high-pressure homogenization, according to Khadka et al.