Cyclobenzaprine pharmacokinetics, including the effects of age, gender, and hepatic insufficiency

J Clin Pharmacol. 2002 Jan;42(1):61-9. doi: 10.1177/0091270002042001007.

Abstract

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 twofold 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.

Publication types

  • Clinical Trial
  • Comparative Study
  • Randomized Controlled Trial

MeSH terms

  • Administration, Oral
  • Adult
  • Age Factors
  • Aged
  • Amitriptyline / analogs & derivatives*
  • Amitriptyline / blood
  • Amitriptyline / pharmacokinetics*
  • Analysis of Variance
  • Area Under Curve
  • Biological Availability
  • Confidence Intervals
  • Cross-Over Studies
  • Dose-Response Relationship, Drug
  • Female
  • Humans
  • Liver Diseases, Alcoholic / metabolism*
  • Liver Diseases, Alcoholic / physiopathology
  • Male
  • Middle Aged
  • Muscle Relaxants, Central / blood
  • Muscle Relaxants, Central / pharmacokinetics*
  • Sex Factors

Substances

  • Muscle Relaxants, Central
  • Amitriptyline
  • cyclobenzaprine