Metabolic fate of fenetylline in rat and man

1. Metabolic fate of 7-[2-(alpha-methylphenylethylamino)ethyl]theophylline hydrochloride (fenetylline) was investigated in male Sprague-Dawley rats and three male volunteers. 2. Six metabolites were identified in the rat urine as amphetamine(AP), p-hydroxy-AP, acetylaminoethyl-theophylline(TP), aminoethyl-TP, hydroxyethyl-TP and carboxymethyl-TP by comparison of their spectral properties and h.p.l.c. and g.l.c. characteristics with those of authentic samples. All these metabolites was also detected in the urine of humans receiving fenetylline. 3. Quantification of these metabolites using h.p.l.c. and g.l.c. showed that carboxymethyl-TP, p-hydroxy-AP and acetylaminoethyl-TP were the major metabolites in 0-24 h rat urine at 13.7%, 11.2% and 9.3% of dose, respectively. In men, carboxymethyl-TP(39-43% dose) and AP(23-33% dose) were the major metabolites in 0-48 h urine. 4. These results suggest that fenetylline metabolism proceeds via oxidative cleavage at two different sites to produce aminoethyl-TP and AP, respectively. The pathway producing AP predominates, in both man and rat, but is more predominant in the former.