Formation and urinary excretion of cyproheptadine glucuronide in monkeys, chimpanzees, and humans

The urinary excretion of cyproheptadine glucuronide (a quaternary ammonium glucuronide) was studied in monkeys, chimpanzees, and humans after a single 5-mg oral dose of cyproheptadine. Humans and chimpanzees excreted, over a 48-hr period, an average 12.4 and 8.6% of the dose, respectively, as cyproheptadine glucuronide. Various species of monkeys excreted less than 0.5% of the dose as the quaternary ammonium glucuronide conjugate. According to these and previously published data, these unusual drug metabolites are excreted in the urine in relatively large amounts only in higher primates.