What is Dissolution?
Dissolution is the process where a solid is introduced into a solvent to yield a solution. Solid oral dosage forms, typically tablets and capsules, are swallowed. Then the tablet begins to disintegrate into large irregular pieces which then further deaggregate into particles. Dissolution begins when the particles are small enough to pass into solution and continues until the tablet has dissolved.
Disintegrating tablets are formulated to break apart to expose the Active Pharmaceutical Ingredient (API) to the solvent.
Disintegration is defined as the point where the dosage form is reduced to a soft mass having no palpably firm core. (US Pharmacopeia <701> Disintegration).
The rate of disintegration can be measured by the disintegration test.
The aggregates break down into discrete particles that greatly increase the surface area creating a solid-liquid interface that facilitates the dissolution phase. Particles are typically less than 0.25 mm in diameter.
In the body, an Active Pharmaceutical Ingredient must be in solution before it can permeate through the gastro-intestinal tract, be absorbed by the blood, and ultimately be carried to the receptor site to render a therapeutic effect (in vivo). The dissolution test verifies the rate of release of drug substance from a dosage form as particles dissolve under simulated physiological conditions (in vitro). Based on this, in vitro dissolution testing may be predictive of in vivo performance.