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Cyclobenzaprine Pharmacokinetics, Including the Effects of Age, Gender, and Hepatic Insufficiency
Author(s) -
Winchell Gregory A.,
King Joyce D.,
ChavezEng Cynthia M.,
Constanzer Marvin L.,
Korn Scott H.
Publication year - 2002
Publication title -
the journal of clinical pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.92
H-Index - 116
eISSN - 1552-4604
pISSN - 0091-2700
DOI - 10.1177/0091270002042001007
Subject(s) - pharmacokinetics , medicine , pharmacology
The pharmacokinetics and bioavailability of cyclobenzaprine, a widely used muscle relaxant, were investigated in four clinical studies, and the effects of age, gender, and hepatic insufficiency were characterized. Cyclobenzaprine plasma clearance was 689 ml/min, and the bioavailability of a 5 mg oral dose was 0.55. Following oral doses of 2.5 to 10 mg tid in healthy young subjects, cyclobenzaprine pharmacokinetics were linear, and plasma concentrations generally increased proportional to dose. There was about a fourfold accumulation of the drug in plasma on multiple dosing, corresponding to an effective half‐life of 18 hours. Steady‐state plasma concentrations of cyclobenzaprine in elderly subjects were twice as high as in young subjects following oral doses of 5 mg tid. Steady‐state plasma concentration also appeared to be up to two fold higher in subjects with mild hepatic insufficiency compared to healthy controls. The magnitude of any difference in steady‐state plasma concentration between males and females appears to be small relative to intersubject variability. A reduction in dose or dosing frequency should be considered in the elderly and in patients with liver disease.