Hepatotoxicity of citalopram in rats and first-pass metabolism.

A chronic oral toxicity study of citalopram in rats revealed dose dependent hepatic fatty infiltrations in male rats while female rats were unaffected. Subsequent studies demonstrated markedly reduced availability due to first-pass hepatic metabolism in male rats and roughly complete availability in females. Pretreatment of male rats with phenobarbital for 2 weeks caused increased metabolism and simultaneous administration of phenobarbital and citalopram gave more pronounced fatty infiltrations than citalopram alone. A connection is suggested between the first-pass metabolism in male rats and the hepatotoxicity, which is possibly mediated through a metabolite or intermediate formed in toxic amount during the first passage of the liver.