COMPARATIVE-STUDY OF THE PHARMACOKINETICS OF FENFLURAMINE, ETHYLAMPHETAMINE, DIETHYLPROPION AND THEIR METABOLITES

Apparent minor chemical changes in the structure of the anorectic agents ethyl-amphetamine, amphetamine, fenfluramine and diethylpropion have major effects on drug distribution, metabolism and elimination from the body. Fenfluramine and ethyl-amphetamine are metabolized by de-ethylation to primary amines with activity and physico-chemical properties similar to that of the parent compounds. They are then metabolized further to inactive compounds. Diethylpropion, however, is metabolized to give a complex mixture of metabolites with various pharmacological actions. Studies have shown that because of the different lipid solubilities of the ionised and non-ionised forms of the drugs, it is essential to control urinary pH at an acid level in man when comparing the differences in their pharmacokinetics. Diet and time of eating can affect urinary pH and, therefore, the rate of elimination of these various anorectics and the duration and character of their pharmacological action. © 1979 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.