Evaluation of carisbamate, a novel antiepileptic drug, in photosensitive patients: An exploratory, placebo-controlled study

Purpose: Carisbamate, a novel neuromodulatory agent with antiepileptic properties, was evaluated in patients with photoparoxysmal responses to intermittent photic stimulation (IPS) in this multicenter, non-randomized, single-blind, placebo-controlled, proof-of-concept study. Methods: Eighteen Caucasian patients (14 females, 4 males) with a mean age of 30 years (range: 16-51 years) underwent standardized IPS under three eye conditions (during eye closure, eyes closed and eyes open) at hourly intervals for up to 8 h after receiving placebo (Day 1), carisbamate (Day 2) and placebo (Day 3). Carisbamate was given at single doses of 250-1000 mg. All patients received one or two concomitant antiepileptic drugs, most commonly valproate. Results: Carisbamate produced a dose-dependent reduction in photosensitivity in the 13 evaluable patients, with abolishment of photoparoxysmal responses in 3 patients and clinically significant suppression of such responses in 7 additional patients. Photosensitivity was abolished or reduced in all five patients in the 1000-mg dose group. The onset of carisbamate occurred rapidly, with clinically significant suppression achieved before or near the time peak plasma drug levels were reached. The duration of action was dose-related and long-lasting, with clinically significant reductions of photosensitivity observed for up to 32 h after doses of 750 or 1000 mg. Carisbamate was generally well tolerated, with dizziness and nausea reported more frequently after active drug than placebo. Conclusion: This study shows that carisbamate exhibits dose-related antiepileptic effects in the photosensitivity model. Randomized, controlled studies of carisbamate in epilepsy patients inadequately controlled by their existing AED therapy are warranted.