Reduced induction of drug metabolism in the elderly.

Young and elderly subjects were given the hypnotic dichloralphenazone (Welldorm) in a dose of 20 mg/kg nightly for two weeks and the extent of induction of liver microsomal drug metabolism was assessed from alteration in the plasma elimination of quinine and antipyrine (phenazone). With both indices, there was a significant increase in plasma drug clearance in young subjects following dichloralphenazone treatment but no significant alterations occured in the elderly group. These results indicate that, in addition to being less able to metabolize some drugs, elderly patients show a reduced induction response. They may therefore be less likely to become tolerant to those drugs which are inactivated by metabolism.