Pharmacokinetic considerations of antidepressant use in the elderly.

The elderly can be more difficult to treat with antidepressants than are young adults. Older patients take more medications, which increases the potential for drug interactions. Their altered physiology results in widely variable plasma drug concentrations from standard doses. Pharmacokinetic and pharmacodynamic changes in this population may predispose patients to experience an increased number of adverse events. The newer antidepressants have been studied for pharmacokinetic changes in the elderly compared with younger volunteers. Most antidepressants show some changes, including slower metabolic clearance and an extended elimination half-life, although the changes described are not uniform between drugs. Recommended initial doses are lower for the elderly for all antidepressants, although optimal doses may not differ from those for younger patients once dosing is individualized.