Metabolism of Afloqualone, a New Centrally Acting Muscle Relaxant, in the Rat

Abstract

The metabolism of afloqualone (6-amino-2-fluoromethyl-3-(o-tolyl)-4 (3H)-quinazolinone, AFQ) was studied in rats. AFQ was extensively metabolized by rats after oral administration of ³H-AFQ. Thirteen unconjugated and three conjugated metabolites were isolated from the 24-h urine. Their chemical structures were identified or characterized by infrared (IR), nuclear magnetic resonance (NMR) and mass spectrometry in comparison with synthetic samples. One of the major metabolic pathways of AFQ was acetylation at the 6-amino group followed by hydroxylation of the methyl carbons of the acetyl and 2'-methyl groups. Another important metabolic pathway was the formation of sulfur-containing metabolites in which the fluorine atom at the 2-position of AFQ is replaced by a methylsulfinyl or methylsulfonyl group. These metabolites may be formed via the mercapturic acid conjugate (s) of AFQ. Five metabolites were detected in plasma 1 h after oral administration. They were the N-acetylated and hydroxylated metabolites ; the sulfur-containing metabolites found in the urine were not detected in plasma.