Tricyclic antidepressants (TCAs) taken in large quantities during suicide attempts have altered pharmacokinetics. A significant enterohepatic recirculation delays the final elimination of a large fraction of the drug. The enzymes responsible for TCA benzyl-hydroxylation can become saturated & thus reduce TCA elimination to zero-order kinetics. The elderly have slower rates of drug elimination & thus are particularly susceptible to TCA antidepressants taken in overdose. (85 refs.)