Steady-state plasma concentrations of cis- and trans-10-OH amitriptyline metabolites

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Abstract
Plasma concentrations of the geometric isomers of 10‐OH amitriptyline (10‐OH AT) and 10‐OH nortriptyline (10‐OH‐NT) were determined by reversed‐phase high‐pressure liquid chromatography. Steady‐state concentrations of AT, NT, and the four 10‐OH metabolites were measured in 27 patients taking AT for depression. All of the unconjugated hydroxylated metabolites were usually detectable and trans‐10‐OH NT always predominated. Mean concentrations, expressed as percentage of the sum of all six compounds, were: AT 30%, NT 27%, cis‐10‐OH AT 1.1%, trans‐10‐OH AT 4.0%, cis‐10‐OH NT 4.0%, and trans‐10‐OH NT 33%. Repeated measurements on 10 patients over several weeks indicated that interindividual variations in absolute and relative 10‐OH metabolite concentrations are much greater than day‐to‐day variations. Five patients who also received a phenothiazine had a lower proportion of 10‐OH metabolites. Clinical Pharmacology and Therapeutics (1982) 31, 609–616; doi:10.1038/clpt.1982.85