Variability in weight and drug content of split tablet may put patients at risk of receiving wrong dosage

Back and neck pain sufferers who divide the most frequently prescribed muscle relaxant may be getting anywhere from half to one-and-a-half times the amount of medicine they believe they are taking, suggests a new study examining the practice of tablet splitting. This may place them at an increased risk of encountering side effects such as drowsiness and fatigue from too much medication, according to the study's primary investigator.

Researchers at the Ernest Mario School of Pharmacy at Rutgers, The State University of New Jersey, recently conducted a study to determine the level of weight variability of tablet fragments when the muscle relaxant cyclobenzaprine HCl 10 mg was split into halves with two commonly used devices – a tablet splitter and a kitchen knife. Initiation of the study followed anecdotal reports that patients given a prescription for branded FLEXERIL® (cyclobenzaprine HCl) 5 mg tablets were being advised to split generic cyclobenzaprine HCl 10 mg tablets instead of taking the 5 mg tablet as prescribed by their physician. FLEXERIL® 5 mg, approved by the U.S. Food & Drug Administration in February 2003, is comparable in efficacy to the 10 mg strength, but has been shown to be less sedating.

"Ideally, an evenly split 10 mg tablet should have 100 percent of the half tablet weight and 5 mg of the medication," explained study investigator Thomas J. Cook, Ph.D., assistant professor, Department of Pharmaceutics. "In this study, the variance in estimated drug content due to uneven tablet splitting ranged anywhere from 50 to 150 percent of the ideal targets, meaning a patient would have no guarantee of receiving a full half-dose consistently throughout the course of therapy." According to its labeling, FLEXERIL® 5 mg is recommended as a two-three week adjunct to rest and physical therapy for the relief of muscle spasm associated with acute, painful musculoskeletal conditions.

Since generic cyclobenzaprine HCl 10 mg tablets are not designed for splitting (tablets are not scored), there is an increased likelihood that they will split unevenly, crumble or shatter, according to Dr. Cook. "In this instance, the practice of pill splitting may put patients at risk of receiving too little or too much medication, either depriving them of the intended therapeutic benefit of the medication or exposing them to unintended side effects such as dizziness or tiredness. The best way to be confident that a patient consistently gets the intended amount of medication is to take the 5 mg tablet as prescribed."

The research is consistent with a study in the March/April 2002 issue of the Journal of the American Pharmacists Association (APhA) which found that tablet splitting generally resulted in a lack of uniformity, even when the tablets were scored. The APhA, along with The National Association of Boards of Pharmacy and the American Society of Consultant Pharmacists are among groups opposing mandated tablet splitting by patients. The newly published "Tablet Splitting: Evaluating Appropriateness for Patients – Tool for pharmacists from the 2003-2004 APhA Strategic Directions Committee" appears in the May-June Journal of the American Pharmacists Association.

About the Study

Dr. Cook, a licensed pharmacist, and two fourth-year PharmD students at the Ernest Mario School of Pharmacy conducted the study, which evaluated the weight variability of 90 cyclobenzaprine HCl 10 mg tablets. Each of the three participants split a total of 30 tablets – 15 each with a commonly used tablet splitting device and a kitchen knife.

Prior to splitting, each whole tablet was weighed on a special scale and the weight was recorded. The participants practiced the splitting technique with each device with up to four tablets; the weights of which were not included in the analysis.

After each tablet was split, the individual fragment weights were measured and recorded. A theoretical half-fragment weight (THW) was used to calculate percent weight and drug content ranges from the average weight of the tablets for each trial.

McNeil Consumer & Specialty Pharmaceuticals, a division of McNeil-PPC, Inc., U.S. marketers of FLEXERIL® 5 mg tablets, sponsored the study.

About FLEXERIL® 5 mg

FLEXERIL® 5 mg should be used for relief of painful muscle spasm along with rest and physical therapy. It should only be used for short periods of time, usually two-three weeks.

FLEXERIL® 5 mg is a prescription medicine and should not be taken by patients who have had a recent heart attack or have heart disease. It should not be used by people with an overactive thyroid or who are currently or have recently used MAOIs. Use of FLEXERIL® 5 mg with MAOIs can result in serious health complications.

FLEXERIL® 5 mg may enhance the effects of alcohol and other medicines that work on the central nervous system. In clinical studies the most common side effects were drowsiness, dry mouth and fatigue. For more information about FLEXERIL® 5 mg, including full U.S. Prescribing Information, visit www.flexeril.info or call 1-888-440-7903.

Reference herein to Rutgers, The State University of New Jersey, the Ernest Mario School of Pharmacy or faculty members of these institutions is intended for identification only and does not constitute an express or implied endorsement or recommendation by the institutions or their agents. http://www.jnj.com