Re-evaluation of the metabolism and excretion of diethylpropion in non-sustained and sustained release formulations.

A direct gas chromatographic method for unstable amino ketones, using a neutral column and moderately alkaline conditions during extraction has been developed. Its application has given a new perspective to the relative importance of the metabolic routes in the complex metabolism of diethylpropion which after oral administration in man is rapid and extensive (only 3-4% of the drug remains unchanged). Mono-N-de-ethylation is the main pathway (about 35% of the dose). N-De-ethylation is more important than carbonyl-reduction, occurring mainly with the unchanged drug (about 20% of the dose). Norephedrine, thought previously to be one of the main metabolites, has been shown to be present only in negligible amounts. About 30% of the dose, which cannot be accounted for as the sum of the amines recovered in urine, is probably metabolized by deamination, followed by oxidation and conjugation to give hippuric acid.