Chapter 27. Pharmaceutics, Pharmacokinetics and Biopharmaceutics

Abstract

This chapter analyzes different phenomena of importance in pharmaceutics, pharmacokinetics, and biopharmaceutics. The phenomenon of drug dissolution, diffusion, and interaction continue to be of paramount importance in the overall picture of drug absorption by the body. Dissolution rates of benzoic acid in surfactant solutions were much less than those anticipated on the basis of solubilization data. The ratios of these dissolution rates in the surfactant solution to those in pure solvent were found to be much greater under static conditions than those under stirred conditions, suggesting a difference in the dissolution mechanism. Dissolution rates of benzocaine were determined in water and polysorbate using both the propeller-driven stirrer and the rotating disc method providing a unique method for distinguishing dissolution mechanisms. The data in the above study confirmed the fact that the rotating disc model rather than the diffusion layer model is operative under stirred conditions and that the Danckwert's model is operative under static conditions. The quantification of the distributions of acute doses of a drug and its metabolites in the multi-compartmental complex organism and its rates of metabolism and excretion are also discussed in the chapter.