Concomitant intake of nortriptyline and carbamazepine

A 73-year-old woman with bipolar manic-depressive illness was treated with nortriptyline, 75 mg/day, for more than 2 years. At this dose her mean (+/- SD) serum nortriptyline concentration (SNT) was 355 +/- 49 nM (n = 13). Nevertheless, the patient again was depressed and was admitted to initiate prophylactic treatment with carbamazepine. During concomitant intake of 500-600 mg/day carbamazepine, the SNT decreased to 140 and 134 nM and the depression persisted. The nortriptyline dose was therefore increased to 150 mg/day; the mean SNT rose to 402 +/- 69 nM (n = 4) and the depression disappeared. This case shows that carbamazepine induces nortriptyline metabolism.