Metabolic fate of strychnine in rats

1. The urinary and faecal excretions of radioactivity, in rats dosed with 3H-strychnine at 0.5 mg/kg subcutaneously, were approx. 30% and 65% of the dose in 7 days, respectively. The radioactivity was mostly excreted within 24 h. 2. Approx. 6% and 3% dose was excreted into urine and faeces, respectively, as unchanged strychnine. 3. Urinary metabolites were extracted from rat urine and purified by silica gel column, t.l.c. and h.p.l.c. Six urinary metabolites, namely, strychnine N-oxide, 21 alpha,22 alpha-dihydroxy-22-hydrostrychnine, 21 alpha,22 beta-dihydroxy-22-hydrostrychnine, 2-hydroxy-strychnine, strychnine 21,22-epoxide and 16-hydroxystrychnine, were identified by comparison with authentic samples by g.l.c.-mass spectrometry. The major metabolites of strychnine in vivo was strychnine 21,22-epoxide.