Gabapentin Treatment of Burning Mouth Syndrome

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Gabapentin Treatment of Burning Mouth Syndrome

Burning mouth syndrome (BMS) is a debilitating disorder consisting of persistent and painful oral burning sensations of the mouth, particularly on the tongue, hard palate, and inner lip, in the absence of mucosal abnormalities.1 Affecting women more frequently than men, BMS has a prevalence rate of 2.5% to 5%. The pain from BMS lasts an average of 2–3 years and in most cases is unremitting, although levels may vary throughout the day.2,3 Local causes of BMS include candidiasis, food allergies, and potential friction on the oral mucosa caused by dentures. Common systemic causes include anemia, diabetes mellitus, menopause, anxiety, depression, smoking, and medications such as diuretics, clonazepam, and antidepressants.1,4-6

Interestingly, while tricyclic antidepressants (TCAs), selective serotonin reuptake inhibitors (SSRIs), and clonazepam have been reported to cause BMS,5-7 in other cases they have been effective remedies for this condition.1,8-10 Now comes a report on the effectiveness of the anticonvulsant gabapentin for the treatment of BMS.11

A 67-year-old woman presented to the Smell and Taste Disorders Clinic at State University of New York Upstate Medical University in Syracuse with a chief complaint of burning pain in the mouth and caustic-tasting saliva. She had experienced an abrupt onset of pain in the right side of her mouth and tongue that gradually spread to the entire mouth 2–3 years earlier. At this initial visit, there may have been small lacerations on the inside of her cheeks. At approximately the same time she began to notice that the taste of her saliva was “strong, caustic, chemical, metallic, or bitter.” While previously she rated the strength of this unpleasant salivary taste as level 3–4 on a scale of 1–10, during the year prior to her visit the burning sensation had gradually increased in intensity to a 10 on the same scale, at times becoming powerful enough to arouse the patient from sleep. She tried various treatments including amitriptyline, cephalexin, erythromycin, and viscous lidocaine; however, none of these medications relieved her symptoms.

At the time of presentation to the clinic, the subject had been evaluated by 18 different physicians, including gastroenterologists, otolaryngologists, neurologists, rheumatologists, and dentists. Previous testing included magnetic resonance imaging scans, the Schirmer test, a histologic evaluation of her lower lip, and measurements of her sedimentation rate, antinuclear antibody titer, rheumatoid factor screening, serum iron level, total iron-binding capacity, ferritin, triiodothyronine uptake, thyrotropin, and folate, all of which were within normal limits. The patient’s medical history was significant for chronic erosive gastritis, esophagitis, pyloric ulcer, hiatal hernia, diverticular disease, hyperlipidemia, and fibromyalgia. At the time of evaluation, she was taking nabumetone for fibromyalgia and ranitidine for her gastrointestinal conditions, but no other medications.

When queried about the effect of BMS on her life, the subject reported feeling discouraged and anxious to obtain relief but denied being depressed or suicidal. Otorhinolaryngologic evaluation was within normal limits. Oral examination revealed a slightly pink mucosa without any sign of inflammation. There were slight fissures on the anterior part of the tongue but no swelling, redness, or other abnormality. The saliva pH was 6.8 and dental work was in good repair. Olfactory testing via the University of Pennsylvania Smell Identification Test was also within normal limits. Gustatory ability was somewhat impaired, with the patient identifying only 16 of 36 tastants on a spatial taste test, although her intensity ratings were in the normal range. Chemosensory testing demonstrated an increased intensity of oral burning after anesthetization of the entire oral cavity, indicative of a release of inhibition and of a centrally mediated pain syndrome. A neurologic examination revealed slightly decreased vibrations in the lower extremities and slightly decreased pinprick perception in an L4-5 distribution on the left.

Given the patient’s dual sensory complaints of BMS and fibromyalgia, it was theorized that she may have been suffering from an idiopathic sensory neuropathy or ganglioneuritis. She was started on nortriptyline 50 mg/day. However, her symptoms persisted and she began to experience an increasingly dry mouth. As a result, nortriptyline was replaced with sertraline, which was gradually increased from 50 mg/day to 100 mg/day and then to 150 mg/day over the course of a year. After having been on sertraline 150 mg/day for 2 months, the patient reported an approximately 50% reduction in the level of oral pain. Sertraline subsequently had to be discontinued due to diarrhea.

Next, due to reports of its efficacy in other pain syndromes, such as diabetic neuropathy and trigeminal neuralgia, gabapentin was initiated at 800 mg/day, then increased to 300 mg TID. Soon after, the patient reported that the burning sensation in her oral cavity had decreased substantially, rating it as 2 on a 1–10 scale, and that her fibromyalgia had also improved. She denied any side effects and at last follow-up had been doing well with gabapentin for the past 3 years.

While the pathophysiology of BMS is not known, some have viewed it as a phantom pain syndrome associated with a release in the inhibition normally exerted by cranial nerve VII on cranial nerves V and IX.12,13 The primary inhibitory neurotransmitter in the brain, γ-aminobutyric acid (GABA), increases neural inhibition and should therefore decrease the oral burn. The effectiveness of the GABAergic drug gabapentin in alleviating BMS in this patient is consistent with this explanation. Gabapentin is an anticonvulsant indicated for adjunctive therapy in the treatment of partial seizures, with and without secondary generalization, in adults with epilepsy. Gabapentin has also been used off-label for a number of other medical and psychiatric conditions including anxiety disorders,14-17 somatization disorder,18 tinnitus,19 ciguatera poisoning,20 and neuropathic pain.21,22 Gabapentin is well absorbed, renally excreted, does not bind to plasma proteins, and has few, if any, drug interactions. The most frequent adverse effects are drowsiness, dizziness, ataxia, gastrointestinal upset,23 and, on occasion, anorgasmia.24-26

Given the severity of BMS and the absence of well validated remedies, gabapentin may be worth considering as a treatment option. Placebo-controlled, double-blind trials are indicated to confirm these preliminary anecdotal findings.


© 2009 Primary Psychiatry a Publication of MBL Communications