Nortriptyline, the N-demethylated metabolite of amitriptyline, is as effective as imipramine in the treatment of depressive episodes of major depression and bipolar disorder. It may also be useful in dysthymic disorder and atypical depression.Plasma concentrations <50 ng/mL are thought to be ineffective and those >150−175 ng/mL are often associated with a suboptimal response in patients with major depression; therefore, excessive dosage may diminish responsiveness. In addition, active metabolites of nortriptyline may accumulate in elderly patients, and toxic side effects may develop despite plasma nortriptyline concentrations <150 ng/mL; however, in one study, the pharmacokinetic parameters of nortriptyline in frail elderly patients were similar to those in younger individuals. Nortriptyline may be less likely than other tricyclic agents to produce orthostatic hypotension, particularly in the elderly. It also may be relatively safer than other tricyclic antidepressants in cardiac patients, including those who have received a transplant
Serum or plasma
Red-top tube, lavender-top (EDTA) tube, or green-top (heparin) tube. Do not use a gel-barrier tube. The use of gel-barrier tubes is not recommended due to slow absorption of the drug by the gel. Depending on the specimen volume and storage time, the decrease in drug level due to absorption may be clinically significant.
Transfer separated serum or plasma to a plastic transport tube. For therapeutic monitoring, collect specimen immediately prior to next dose.