Excessive plasma concentration of tricyclic antidepressants resulting from usual doses: a report of six cases.

Six patients are described who achieved very high plasma concentrations of imipramine and desipramine during chronic therapy with usual doses. Side effects were minimal. Speculation as to apparent tolerance includes the presence of low metabolite concentrations. Plasma concentration monitoring may be indicated to identify the occasional patient who achieves potentially toxic plasma concentrations while taking recommended doses of tricyclics.