[Severe nortriptyline poisoning in poor metabolizers of the sparteine type]

Approximately 7% of the Danish population are so called poor metabolizers (PM) as regards the model compound sparteine. These individuals lack the P450 isozyme which is mainly responsible for elimination of at least 20 different medicaments including nortriptyline. A woman aged 42 years suffering from depression was treated with 100 mg nortriptyline daily and, during the course of treatment, she developed a toxic serum nortriptyline level (approximately 2,100 nM). Treatment was withdrawn temporarily on account of severe side-effects. The depression recurred. During the medicine-free period, a sparteine test was performed and this demonstrated that the patient was a poor metabolizer. Scarcely two months after hospitalization, treatment was recommenced with 25 mg nortriptyline daily after which the patient's depression disappeared completely without any side-effects of note.