Effects of marketed antiepileptic drugs and placebo in the human photosensitivity screening protocol

A study of epilepsy patients with a reproducible range of photoparoxysmal responses (PPR) (epileptiform discharges evoked by flashing lights) has been used as a "proof-of-concept" trial to determine if novel potential antiepileptic drugs (AEDs) should proceed in development. The standard design for this trial requires a 3-day inpatient stay and is single-blind. We evaluated two marketed and effective AEDs-one narrow-spectrum [carbamazepine (CBZ)], and one broad-spectrum [levetiracetam (LEV)]-using a novel double-blinded, cross-over outpatient version of the trial to detect acute drug effects of the two marketed AEDs on photosensitivity. We tested 6 patients with a known stable photosensitivity response, using single oral doses of CBZ 400 mg and LEV 1000 mg, compared to 2 test days with single placebo doses. Patients who received LEV had the lowest mean PPR (compared with placebo and CBZ). The mixed effect model showed a significant effect of LEV in all eye closure conditions (p < 0.001). There was no evidence of a significant change in PPR after CBZ or placebo treatment. In conclusion, LEV 1000 mg, but not CBZ 400 mg, was effective in suppressing photosensitivity within a 6-h period compared with placebo showing the ability of our novel photosensitivity trial design to demonstrate effects of broad-spectrum AEDs. We cannot confirm the ability of the photosensitivity trial to detect the narrow-spectrum AED CBZ in our design. The novel outpatient study design is feasible and is expected to reduce costs compared with previous methodology.