Importance of the field: Cyclobenzaprine immediate-release (CIR) is a widely prescribed skeletal muscle relaxant with an established efficacy and safety profile in patients with muscle spasm associated with acute, painful conditions, although it is commonly associated with sedation. CIR is typically prescribed at a dosage of 10 mg three-times-daily. This review focuses on the pharmacokinetic profile of a new formulation, cyclobenzaprine extended-release (CER), which delivers a sustained plasma cyclobenzaprine concentration over 24 h, allowing once-daily dosing.
Areas covered in this review: Results from CER pharmacokinetic studies conducted through August 2010 are summarized.
What the reader will gain: This review provides information on the first four studies assessing the single-dose and steady-state pharmacokinetic profile of CER.
Take home message: Once-daily CER 30 mg and three-times-daily CIR 10 mg produced comparable systemic exposures to cyclobenzaprine, but pharmacokinetic profiles were qualitatively different. CER was characterized by a single daily peak in cyclobenzaprine concentration versus three peaks/day for CIR. With once-daily dosing of CER, cyclobenzaprine concentration is sustained over 24 h. CER 30 mg provides approximately twice the exposure as CER 15 mg. Systemic exposure to CER is increased in the presence of food and in elderly subjects. Steady-state is achieved by day 7 of dosing.