Estimation of dissolution rate of salicylamide in complexing media using a theoretical diffusion model.

Dissolution rates of salicylamide in water and caffeine solutions under perfect sink conditions were predicted by theoretical diffusion equations applicable to dissolution in complexing media. Experimental dissolution rates were measured using a compartmentalized rotating-basket apparatus under two sets of conditions. Agreement was found between experimental and predicted rates. Use of the theoretical equation for estimating dissolution rates involves simple calculations of diffusion coefficients and diffusion layer thickness under the operative dissolution conditions. The increase in dissolution rate caused by addition of the complexant can be calculated for diffusion-controlled dissolution directly if the stability constant and the drug solubility in water are known or measured.