To the Editor: Methadone maintenance treatment is the most common pharmacological intervention for opioid dependence. In clinical trials (1, 2), about 45% of the patients in established methadone maintenance treatment suffered from excessive sweating.
Biperiden is an anticholinergic drug that is well known from clinical use in parkinsonism and schizophrenia. We present what we believe are the first reported cases of methadone-induced excessive sweating that were successfully treated with biperiden. During the observation period, all three patients had no additional medication, and none of them reported adverse effects such as sedation, dizziness, dryness of the mouth, or blurred vision.
Mr. A was a 30-year-old computer technician who had suffered from excessive sweating since adolescence. He tested different treatments, including Salvia tea, benzodiazepines, carvedilol, and atropine drops, but none of them worked. After entering methadone maintenance treatment (current dose: 50 mg/day), he suffered intolerable sweating, especially at business meetings. After he received biperiden during a psychiatric emergency to antagonize the extrapyramidal side effects of a typical antipsychotic, he noticed a cessation of sweating for several hours. With a dose of 2–4 mg/day of biperiden 3–4 days per week, we could reproduce and maintain this positive effect.
Mr. B was a 43-year-old electrician who had started methadone maintenance treatment 3 years earlier. He had never had a problem with sweating, but from the first day of taking methadone and independently of the dose (20–90 mg/day, currently 40 mg/day), he had to change his wet clothes numerous times a day and suffered from negative reactions at his workplace. Treatment with biperiden resulted in a prompt and stable cessation of the generalized sweating (current dose: 2 mg/day).
Mr. C was a 37-year-old man who had been taking methadone for 6 years (current dose: 18 mg/day). He had had a problem with sweating previously, but with methadone, it became much worse: "In the summer I felt like a hydrant. It was really crazy." Seeking help, he tried several remedies without any success. Finally, biperiden (a 4-mg controlled-release tablet every morning) resulted in an effective control of the symptom.
Little is known about the exact mechanisms by which methadone influences autonomic thermoregulatory control and produces increased sudomotor activity. However, the mainly centrally acting antimuscarinic agent biperiden appears to antagonize this overactivation very efficiently.
Recovery from opioid addiction can be a long-term process and requires prolonged periods of methadone maintenance treatment. Excessive sweating due to methadone may be so disturbing in the long run that the question arises if this is an important and yet underestimated reason for premature dropouts and treatment failures. Patients with a high level of psychosocial functioning seem to suffer from it especially. We think that the treatment of this important side effect needs more concern and that biperiden in a dose of 2–4 mg/day could be a significant contribution toward overcoming this treatment complication.