The ability of patients to accurately detect when they would need to use Flexeril 5 mg (cyclobenzaprine) is a significant hurdle the drug would need to overcome in a switch from the Rx to the OTC environment, according to discussions by FDA's Nonprescription Drugs and Arthritis Advisory Committees July 20.

At the meeting, a formal vote was not taken on whether the product should be allowed for sale over-the-counter. FDA will consider the joint committees' comments in its review of the switch; neither the agency nor Merck specified whether a second committee review was likely to occur.

The proposed indication for OTC Flexeril is: "Relieves painful muscle tightness and spasm of back or neck due to recent strain, overuse or minor injury." The drug would likely be named Flexeril MR if marketed OTC; Merck would probably continue to market a 10 mg Rx version. The committee's discussion focused on the question: "Is muscle spasm of the back or neck a consumer self-diagnosable condition?"

Arthritis Committee Chair Steven Abramson, MD, Hospital for Joint Diseases, New York City, commented, "It's a difficult thing to expect patients to make an accurate diagnosis." Relying on the patient might not be advisable, he said, and "one of the hazards might be that a greater proportion of people with back pain or other pain not due to spasm may begin to use this drug."

"With low back and neck pain, it's hard even for physicians often to understand where that pain is coming from," Abramson noted. Due to this difficulty, he said data on the "reliability of the patients diagnosing muscle spasm or tightness versus arthritis" would be helpful, since "we're relying on the patient to make that distinction."

Daniel Lovell, MD, Children's Hospital Medical Center, Cincinnati, commented on the fact Merck did not conduct a study examining "patients who say they have back spasm and then subsequently [are] evaluated by a physician to test the accuracy of that self-diagnosis."

Nigel Harris, MD, Morehouse School of Medicine, Atlanta, said "headache or menstrual cramps... [are] conditions that I feel relatively confident people can easily self-diagnose." Flexeril's indication, however, "is in a separate category," he said.

NDAC Chair Eric Brass, MD/PhD, Harbor-UCLA Medical Center, Los Angeles, noted "if you knew that when a consumer said 'I have back pain' that, in fact, independently you could say that 98% of them have muscle spasm, that would relieve your concern, but I'm not hearing any data set that looks like that."

When asked about the leading causes of back pain, David Borenstein, MD, George Washington University - a consultant to Merck - conceded "the answer to that depends...on the age range. You'll have more arthritis in the older group, while the younger group will have it more on the basis of muscle" problems.

Due to the difficulty inherent in determining the cause of most back and neck pain, additional concerns were raised regarding potential misuse of Flexeril as an analgesic. "I'm still not convinced that patients won't take this as they might an analgesic for back and neck pain alone, that it will end up being, in the minds of many patients, an analgesic rather than being used for spasm," Morehouse's Harris stated.

Hari Sachs, MD, Coleman, Coleman and Sachs, asked "if you gave this medicine to a consumer who is experiencing pain, would a serious diagnosis be missed...for example, with somebody who really has a slipped disc." Brass asked the committee if there are "any patients for whom the use of a muscle relaxant would be used as first-line therapy before initiating, or at the same time as initiating, analgesic therapy."

Arthritis Committee member David Yocum, MD, University of Arizona, explained that many rheumatologists may use muscle relaxants first line for fibromyalgia, but "unless I detect clear muscle spasm that I feel comfortable with...I would go to an analgesic, and even in the case of muscle spasm, I might do that anyway."

Abramson noted there are no solid comparative data on analgesics and muscle relaxants, but said the reason "we may often use analgesics or anti-inflammatories is the muscle spasm...is secondary to whatever the primary problem is."

Richard Neill, MD, University of Pennsylvania College of Medicine, said FDA should consider NSAIDs or other analgesics in comparison to muscle relaxants due to the possible superiority of one over the other, and the potential for consumer confusion between the two.

If patients "cannot distinguish between [Flexeril] and an analgesic, and they cannot then logically place [Flexeril] in a sequence that would give them the best chance for improvement with the lowest chance for side effects," the drug may not be appropriate for OTC sale, Neill stated.

Flexeril Indications Self-Diagnosis Seen As Significant Hurdle By Committee

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