USA. Elan Pharmaceuticals has issued a ‘Dear Healthcare Professional’ letter in the US advising prescribers of important updates to the prescribing information for zonisamide (Zonegran) used in the treatment of refractory epilepsy. The update provides new information about oligohidrosis and hyperthermia in paediatric patients. The company says that, as of December 2001, there have been 40 reported cases of oligohidrosis and hyperthermia in paediatric patients. 38 cases were reported during the first 11 years of marketing in Japan and 2 cases were reported in the first year of marketing in the US, providing estimated reporting rates of 1 and 12 cases per 10,000 patient-years of exposure, respectively. The cases typically involved decreased sweating and elevated body temperatures and many were reported after exposure to elevated environmental temperatures. Some patients developed heat stroke requiring hospitalisation, but no deaths have been reported.

The company says that paediatric patients appear to be at an increased risk of zonisamide-associated oligo-hidrosis and hyperthermia. Patients, particularly paediatric patients receiving zonisamide should be monitored for evidence of decreased sweating and elevated body temperature, particularly in warmer weather. Prescribers are also advised to use caution when prescribing zonisamide with other drugs that may predispose patients to heat-related disorders such as carbonic anhydrase inhibitors or drugs with anticholinergic activity.

Elan Pharmaceuticals also notes that the safety and efficacy of zonisamide in paediatric patients has not been established and that zonisamide is not approved for use in paediatric patients.

Reports in WHO-file: Sweating decreased 13

Reference:

‘Dear Healthcare Professional’ letter from Elan Pharmaceuticals Inc, Jul 2002.
Available from URL: http://www.fda.gov/medwatch/ SAFETY/2002/safety02.htm#zonegr