Use of Clozapine in persons with a history of seizures: A retrospective study

Seizures are considered to be one of the dreaded side effects of clozapine, and due to this, the use of clozapine is avoided in patients with treatment-resistant schizophrenia. Resultantly, there is little information about the use of clozapine among patients with seizure disorder.

To assess the safety of clozapine in patients with history of seizures in their lifetime before starting clozapine and receiving clozapine for the management of psychotic disorders.

Out of the 958 patients, 35 (3.65 %) had a history of at least one seizure episode before starting clozapine, with a mean of 5.06 (SD: 7.23; Median: 3.00) seizures before starting clozapine. The mean duration between the last seizure and the starting of clozapine was 123.75 (SD: 124.99; Median: 84) months, with nine patients having an episode of seizure in the previous 12 months and 15 patients being seizure-free for more than ten years. About one-fourth (25.7 %; nine out of 35) of the patients had recurrence of seizure while receiving clozapine for a mean duration of about five years. When the recurrence of seizure after starting clozapine was evaluated in patients receiving antiepileptics along with clozapine, the incidence of at least one seizure was 26.67 % (4 out of 15), and among those not receiving antiepileptics, the incidence of at least one seizure was 25 % (5 out of 20). The dose of clozapine at which seizure was noted ranged from 12.5 mg to 600 mg/day with a mean of 236.25 (SD: 169.04; Median: 162.5) mg/day. In none of the patients, clozapine had to be stopped due to the continuation of seizures.

About one-fourth of the patients with history of an episode of seizure have recurrence of seizure while receiving clozapine. The demographic and clinical variables do not differ between those who develop and who do not develop seizures after starting clozapine, including concomitant use of antiepileptics.