CLEVELAND-For people who suffer from burning mouth syndrome, low doses of the drug clonazepam may offer significant relief, according to a study by a Case Western Reserve University professor in the November issue of Oral Surgery.
About 1.3 million American adults, mostly postmenopausal women, are afflicted with burning mouth syndrome (BMS), a chronic, often debilitating condition whose cause remains a medical mystery. Only in recent years has science begun to seek an organic basis for the intense burning pain, notes researcher Miriam Grushka, an associate professor of oral diagnosis at the CWRU School of Dentistry.
"Until the late 1980s or early '90s, it was treated as an emotional problem that was thought to be associated with depression, anxiety, or other neuroses," says Grushka, a pioneer in the treatment of BMS. Although recent research has focused on various physical explanations for burning mouth, there is no consensus on the cause or treatment.
BMS seems to follow a pattern in many sufferers, Grushka observes. The burning pain begins by late morning and usually reaches peak intensity by evening, which makes falling asleep difficult yet doesn't awaken the patient during the night.
Grushka's study tested the effect of clonazepam, a form of benzodiazepine that is often used an anticonvulsant. Her sample consisted of 30 patients who had experienced BMS for anywhere from one month to 12 years. One subject was an 83-year-old male and the rest were females age 45 to 87 (with a median age of 65).
The patients began taking 0.25 mg of clonazepam at bedtime for one week and could increase the daily dose by as much as 0.25 mg each week, up to a total dosage of 3 mg.
"Patients were carefully instructed about increasing the dose only until they either experienced significant pain relief or until they experienced untoward side effects, especially drowsiness," Grushka reports.
At the conclusion of the study, 43 percent of the patients reported partial to complete relief and were still using the medication. Twenty-seven percent found the drug helpful but quit using it due to side effects, usually drowsiness. For the remaining 30 percent, the clonazepam offered no relief.
When Grushka compared patient age, history of BMS, and final dose levels among these three groups, she found that patients in the group that got the most relief were significantly younger than those in the group that had some relief, but side effects. Those who got the most relief also had shorter histories of BMS and got relief with lower doses of clonazepam than either of the other two groups.
Since a total of 70 percent of subjects experienced reduced pain, Grushka believes clonazepam may be the best available treatment for many BMS patients. "When it works, it's really dramatic," she says. "The pain just disappears."
Many BMS patients also experience taste disturbances, usually a persistent bitter taste. "When the clonazepam works, it also wipes out the funny taste," Grushka says. "This is the first published treatment for altered taste."
In August, Grushka and a co-author presented a review of current knowledge about BMS at the World Workshop on Oral Medicine in Chicago at the American Dental Association headquarters.
"For the majority of BMS subjects, the onset of pain is usually spontaneous with no known precipitating factors," they reported. However, from 34 to 43 percent of subjects relate the onset to a previous dental procedure or illness, such as an upper respiratory infection. Grushka believes this points to nerve damage as a possible cause. As an anticonvulsant, the clonazepam may prevent spontaneous firing of the cranial nerve that carries sensations of pain to the brain.
Eating seems to relieve the pain, which supports the nerve damage theory, according to Grushka. If the cranial nerve that senses taste were damaged, she explains, the cranial nerve that senses pain could be spontaneously sending pain messages to the brain even though there is no stimulus for the pain. When the BMS patient eats, this stimulates the taste nerve to send taste messages to the brain and stops the spontaneous firing of the pain nerve.
Even though eating offers relief from the pain of BMS, Grushka adds, BMS sufferers do not usually become overweight.
Journal
Oral Surgery