Effect of Valproic Acid Concentration on Photic Response

The investigators will utilize intravenous sodium valproate at visit 3. Dosage will be individualized to each patient's body weight, age, and hepatic-enzyme-inducing status. Intravenous VPA dose predictions will be based upon population VPA pharmacokinetic parameters (Dutta 2003).

Each patient will have a placebo-infusion (with 0.9% NS or D5W) of 12-hour duration at visit 2.