Bupropion-induced acute dystonia

OBJECTIVE: To report a case of acute dystonia consisting of neck stiffness, trismus, and unilateral temporomandibular joint (TMJ) pain and subluxation secondary to an increase in sustained-release (SR) bupropion. CASE SUMMARY: A 44-year-old white man with a history of chronic low-back pain and tension headaches, taking no other medications, was started on bupropion SR 150 mg once a day for depression. The dosage was increased to 150 mg SR twice a day and eventually augmented with buspirone 15 mg 3 times a day. He developed bilateral trismus, inability to rotate his head laterally, and spontaneous left TMJ subluxation. Symptoms recessed with discontinuation of both medications and failed to reappear with a trial of buspirone 15 mg 3 times a day alone. A retrial of bupropion alone evidenced no adverse effects at a dosage of 150 mg SR once a day. However, when the dosage was increased to 150 mg SR twice a day, the patient reexperienced initial signs of neck stiffness, jaw muscle tightness, and left TMJ subluxation within 24-48 hours. Reduction of the bupropion dosage to 150 mg SR once daily stopped the symptoms; the patient has continued at this dosage without adverse effects for > 1 year. DISCUSSION: Medication-induced focal dystonias usually present with dramatic head (most frequently oral-buccal) and neck muscle spasm with occasional jaw clenching, bruxism, and TMJ syndrome. In this case, the rapid onset of neck and jaw symptoms within 24-48 hours of an increase of bupropion SR from 150 mg once a day to 150 mg twice a day suggest that the patient may have been sensitized by an initial trial of bupropion and buspirone, or by the increased dose of bupropion alone. Both agents are reported to interact with both the dopaminergic and serotonergic systems. Although buspirone has been implicated in inducing acute dystonia, it did not do so in this case when used alone at a dose of 45 mg a day. During a second trial of bupropion SR 150 mg a day, neck and jaw symptoms recurred within 24-48 hours of increasing the dose to 150 mg SR twice a day. The symptoms receded when the bupropion dose was returned to 150 mg SR once a day, suggesting a dose-response relationship. The Naranjo probability scale indicated that this untoward reaction was probable. CONCLUSIONS: This case suggests that selected patients may experience dose-related acute dystonic adverse reactions to bupropion with or without buspirone augmentation. Dystonias, which usually follow administration of antipsychotics, have been linked to acute dopamine depletion and basal ganglion-derived gamma synchronization dysfunction. Acute dystonia symptoms may begin within hours of starting or changing antipsychotic drug dosage; however, 90% of symptoms are observed during the first 3-5 days of starting or increasing dosage. To the best of our knowledge, there have been no reports of bupropion-induced dystonia.

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