Clinical effects of allopurinol on intractable epilepsy

We studied the clinical efficacy of allopurinol as add-on therapy in 31 patients with intractable epilepsy. When administered for a short time, allopurinol was effective in 17 patients (55%); 8 were seizure-free, 8 had 75% decrease in seizure frequency, and 1 had greater than 50% decrease. Allopurinol was most effective in patients with localization-related epilepsy, especially in secondarily generalized tonic-clonic seizures. Allopurinol was not as effective in patients with Lennox syndrome or West syndrome, or in severe myoclonic epilepsy in infants. When allopurinol was administered greater than 1 year, its initial effectiveness continued in 8 of 14 patients who exhibited initial improvement. In 2 of the remaining 6 patients, the initial improvement disappeared during the course of treatment but control was regained by increasing the dosage of allopurinol. Mild side effects were observed in 4 patients (13%): drowsiness in 3 and abdominal pain in 1. Allopurinol may be a useful antiepileptic drug (AED), and a double-blind placebo-controlled trial should be performed.