Mass spectrometric identification of DL-verapamil metabolites

DL-verapamil [2,8-bis(3,4-dimethoxyphenyl)-6-methyl-2-isopropyl-6-azaoctanitrile; Isoptin] is metabolized in man by N-dealkylation -- mainly by cleavage of the N6-C7 bond -- and by demethylation of the methoxy groups. After oral administration, besides unchanged verapamil, 12 metabolites could be isolated from urine and their structures were elucidated by (GC-) mass spectrometry.