Cyclobenzaprine 
(Trade Name: Flexeril^®)

September 2007 DEA/OD/ODE

Cyclobenzaprine is a central nervous system (CNS) muscle relaxant intended for short-term use in the treatment of pain, tenderness, and limitation of motion caused by muscle spasms. Although not controlled under the Controlled Substances Act (CSA), cyclobenzaprine may enhance the effects of other CNS depressants including alcohol, barbiturates, benzodiazepines and narcotics and anecdotal reports indicate it is used nonmedically to induce euphoria and relaxation.

Licit Uses:

Cyclobenzaprine HCl is approved for use in the United States as a muscle relaxant. It is marketed in brand name (Flexeril^®) and generic formulations in 5, 7.5, and 10 mg tablets intended for short-term (2 to 3 week) oral administration. Usual starting dose is 5 mg three times a day. The maximum recommended dose is 10 mg three times daily.

Cyclobenzaprine HCl is a white crystalline tricyclic amine salt that is freely soluble in water or alcohol.

Cyclobenzaprine has been shown to reduce or abolish skeletal muscle hyperactivity. It is thought to act within the CNS at brain stem rather than spinal chord levels, although the latter may contribute to some of its therapeutic effect on skeletal muscle relaxant activity. Pharmacological studies in animals have shown a similarity between the effects of the structurally-related tricyclic antidepressants and cyclobenzaprine. The most frequently encountered adverse effects of cyclobenzaprine include the anticholinergic effects of drowsiness, dry mouth and dizziness. Other CNS effects include blurred vision, confusion, anxiety, agitation, psychosis, abnormal thinking, and hallucinations. Cardiovascular effects include increased heart rate and palpitations. The likelihood of experiencing many of these effects is dose related. Nausea, headache and malaise may be experienced upon abrupt termination of prolonged use.

A number of indicators suggest that cyclobenzaprine is being intentionally misused or abused.

According to poison control data, Toxic Exposure Surveillance System (TESS), exposures for cyclobenzaprine are numerous and have resulted in serious medical outcomes and deaths. In 2004, there were over 7,743 cyclobenzaprine exposures reported to TESS with 61 percent classified as intentional use. There were 335 major outcomes (the patient exhibited signs or symptoms as a result of the exposure that were life-threatening or resulted in significant residual disability or disfigurement) and 33 deaths.

According to the National Forensic Laboratory Information System (NFLIS), state and local forensic laboratories analyzed 783 cyclobenzaprine drug items from 724 law enforcement cases in 2006. Massachusetts (84 items), Missouri (90 items), Texas (107 items) and Virginia (121 items) accounted for about a half of all cyclobenzaprine drug items analyzed by state and local laboratories in 2006.

Anecdotal reports found on the Internet suggest that individuals are taking cyclobenzaprine alone or in combination with other illicit drugs to produce or enhance psychoactive effects. Individuals have reported taking cyclobenzadrine both orally and intranasally at doses ranging from 10 mg to about 60 mg. Sedation, relaxation and increased heart rate were the most common effects reported. Euphoria was reported by a smaller number of individuals.

Cyclobenzaprine is not controlled under the CSA.