Dissolution profiles of drugs from tablets.

A theoretical equation to describe the drug dissolution from a tablet was derived by combining and equation for the disintegration rate of a tablet with an equation for the dissolution of particles. The theory is based on the assumptions that: (a) dissolution occurs only from the particles released in a medium by tablet disintegration, (b) the number of particles released into a medium obeys the equation N = NO(T/Td)m, and (c) the dissolution of particles, which are spherical in shape, is represented by the equation previously given by Brooke. Tablet dissolution versus time plots, obtained by calculating the equation with a computer, gave an S-shaped curve between the dissolution curve for particles starting at time zero and the curve for particles starting at the tablet disintegration time. The joint influences of disintegration and particle dissolution on the overall tablet dissolution profile also were examined. When dissolution of powders was rapid, disintegration of a tablet directly influenced its dissolution. When powders intrinsically dissolved slowly, the effect of disintegration on the tablet dissolution profile was slight.