Steady-state plasma concentrations during single and multiple dosage schedules of amitriptyline

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Abstract
SYSNOPSIS: Plasma amitriptyline and nortriptyline concentrations were measured in a group of five adult subjects who each received two different dosage regimes of amitriptyline (Tryptizol) for 14 day periods—namely, 25 mg three times daily and 75 mg once nightly. Mean steady-state plasma concentrations during the two dosage regimes were in close accord. The daily variation in drugplasma concentrations were only minimal during the thrice daily dosage regime but during the once nightly dosage regime there was an average decline in total drug plasma concentrations (amitriptyline plus nortriptyline) of about 30%. It was concluded that antidepressant medication with amitriptyline using a single nightly dose schedule might be more reliably taken by patients without there being any significant reduction in therapeutic efficacy.