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Lower Dose Flexeril (Cyclobenzaprine) Relieves Acute Painful Muscle Spasm With Less Sedation Than Higher Dose

Patients Report Onset of Relief Within 24-48 Hours from the Start of Treatment, According to Studies Published in Clinical Therapeutics

FORT WASHINGTON, PA -- April 14, 2003 -- FlexerilŽ (cyclobenzaprine HCl) 5 mg tablets provide clinically significant rapid relief from the pain of acute musculoskeletal spasm of the back and neck, with less drowsiness than seen in the older 10 mg version of the most frequently prescribed muscle relaxant suggest the authors of two studies published in the April issue of Clinical Therapeutics. And, they add, the ability of Flexeril 5 mg to provide symptomatic relief and reduced recovery time are of potential socioeconomic importance for the approximately 15 to 20 percent of the U.S. population who suffer from low back pain in any given year.

Although the pain of acute musculoskeletal spasm generally resolves in a week with or without treatment for 60 percent of patients, treatment with cyclobenzaprine, the active ingredient in Flexeril 5 mg, has been shown to shorten the time to relief of back/neck symptoms by two days versus no treatment.

The findings suggest that comparable benefits may be derived between Flexeril 5 mg and Flexeril 10 mg. In the pooled results of the studies, the 5 mg and 10 mg strengths of Flexeril demonstrated an ability to relieve muscle spasm pain, regardless of the location of the spasm, versus placebo, but patients taking Flexeril 5 mg reported significantly less drowsiness than patients taking the 10 mg tablet. Patients who received Flexeril 5 mg reported experiencing discernible relief more rapidly than those receiving placebo, with an onset of efficacy observed within 24-48 hours from the start of treatment.

"Two days in a seven-day period translates into 30 percent faster improvement with treatment than without it," said study lead author David Borenstein, MD, FACR, FACP, Clinical Professor of Medicine and former Medical Director of The Spine Center at The George Washington University Medical Center in Washington, D.C. "The sooner a patient obtains relief from pain, the sooner normal activity can be resumed and the lower the medical costs."

Direct medical costs for back pain in the United States totaled $24 billion in 1990, and disability compensation and decreased work productivity accounted for another $75 billion. "The nonmonetary costs of back problems, such as the inability to perform routine daily activities also can be substantial," noted Dr. Borenstein.

The U.S. Food and Drug Administration approved Flexeril 5 mg on February 4, 2003 as a 2-3 week adjunct to rest and physical therapy for the relief of muscle spasm associated with acute, painful musculoskeletal conditions. McNeil Consumer & Specialty Pharmaceuticals is marketing the product in the United States. It reached pharmacy shelves in April, giving physicians greater dosing flexibility for the initial treatment of sprains, strains, and other painful musculoskeletal injuries.

Study Details

Both studies were seven-day, double-blind, placebo-controlled, randomized, multi-center clinical trials. Together, they enrolled 1,405 patients with acute (<14 days), physician-rated moderate or moderately severe painful muscle spasm in the lower back or neck. Concomitant use of analgesics, psychotropic agents and drugs with the potential to cause sedation were prohibited.

Over a one-week course of treatment, patients reported that Flexeril 5 mg provided relief of musculoskeletal spasm symptoms significantly greater than placebo. On average, most patients experienced some, a lot, or complete symptom relief within 24-48 hours of starting treatment with both strengths. Analyses of the data show that Flexeril produces clinical improvement whether or not sedation occurs. "The data demonstrate that the efficacy of Flexeril is not due to sedation," said Dr. Borenstein.

The incidence of sedation was significantly lower in patients taking Flexeril 5 mg compared with those taking Flexeril 10 mg (29% vs. 38%, respectively; 10% for placebo). Most patients who reported sedation developed it on the first or second day of dosing. Most episodes were mild and did not result in discontinuation of therapy. Only two percent of patients reported severe sedation. Clinicians say that a patient who does not experience sedation in the early stages of treatment will most likely not experience drowsiness later in the course of treatment.

Dry mouth, another side effect associated with most muscle relaxants, was also significantly lower in the Flexeril 5 mg patient group compared with the Flexeril 10 mg group (21% vs. 32%, respectively; 7% for placebo). Other adverse events reported in greater than three percent of patients include fatigue and headache.

Musculoskeletal pain

Approximately 15% to 20% of the U.S. population suffers from low back pain in any given year, and according to the federal Agency for Health Care Policy and Research, about two-thirds of adults have low back pain at some point in their lives. In fact, low back pain is the most frequent cause of disability in people under age 45. It is estimated that up to half of all working adults experience back pain each year. Including disability and lost days of work, low back pain accounts for $50 billion in costs annually.

Flexeril should not be taken by patients during acute recovery phase of myocardial infarction or by patients with arrhythmias, heart block, conduction disturbances, congestive heart failure, allergies to cyclobenzaprine or other ingredients in Flexeril, hyperthyroidism, current or recent use (within 14 days after discontinuation) of monoamine oxidase inhibitors (MAOIs). Flexeril may enhance the effects of alcohol, barbiturates, and other CNS depressants. Flexeril may impair mental and/or physical abilities required for performance of hazardous tasks, such as operating machinery or driving a motor vehicle.

Hyperpyretic crisis seizures and deaths have occurred in patients receiving cyclobenzaprine (or structurally similar tricyclic antidepressants) concomitantly with MAO inhibitor drugs. Cyclobenzaprine is closely related to the tricyclic antidepressants, which have been reported to produce arrhythmias, sinus tachycardia, prolongation of the conduction time leading to myocardial infarction, and stroke. Because of its atropine-line action, Flexeril should be used in caution in patients with a history of urinary retention, angle-closure glaucoma, increased intraocular pressure, and in patients taking anticholinergic medication.



SOURCE: McNeil Consumer & Specialty Pharmaceuticals

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