Topiramate (Topamax®, Janssen-Cilag), a sulphamate-substituted monosaccharide antiepileptic, was registered in 1998 in Singapore for the treatment of adults and children with partial onset seizures and generalized seizures.

Janssen-Cilag has revised the local package insert of Topamax® to provide updated information about oligohidrosis (decreased sweating) and hyperthermia. Oligohidrosis and hyperthermia may have potentially serious sequelae, which may be preventable by prompt recognition of symptoms and appropriate treatment.

This updated information is based on clinical trials and post-marketing experience in more than 2 million patients worldwide. The reports have primarily involved children. Most cases have occurred in association with exposure to elevated environmental temperatures and/or vigorous activity, and children should be observed closely under these conditions. In the majority of patients, Topamax® therapy has been continued. Proper hydration before and during activities such as exercise or exposure to warm temperatures is recommended.

As of February 2002, the rate for spontaneous post-marketing reports of all potential cases of oligohidrosis is approximately 35 per 1,000,000 patients treated and 1.6 per 1,000,000 patients treated for serious or medically significant oligohidrosis or its sequelae. It is generally recognized that post-marketing data are subject to substantial under-reporting.

Patients, especially paediatric patients, when treated with topiramate should be monitored closely for evidence of decreased sweating and increased body temperature, especially in warm or hot weather. Caution should be used when topiramate is prescribed with other drugs that predispose patients to heat-related disorders; these drugs include, but are not limited to, carbonic anhydrase inhibitors and drugs with anticholinergic activity.