Valproic acid and phenobarbital blood levels during the first month of treatment with the ketogenic diet

Objective – The aim of this study was to assess how the ketogenic diet influences the blood levels of antiepileptic drugs in the first month of treatmentinapediatricpopulationwithdrug-resistantepilepsy. Methods – The plasma concentrations of antiepileptic drugs were investigated in an open study on 36 consecutive children and adolescents (20 males), aged between 6 months and 16 years (mean age 4.7 years), who were put on the ketogenic diet because of medically refractory epilepsy. The plasma levels of antiepileptic drugs were determined 30 days and immediately before the diet and on days 8, 15, 22 and 29 after the start of the diet. The daily dose of each drug was not changed during the first month of treatment, while the daily dose of benzodiazepines was reduced by up to 30% if excessive sedation or drowsiness occurred. Results – While plasma concentrations of phenobarbital did not change in the first month on the ketogenic diet (mean increase of 2.3 mg ⁄ l 1.0), valproic acid showed a slight but not significant decrease (mean decresase of 6.7 mg ⁄ l 3.2), 2 weeks after the start of the diet. Conclusions – Adjustments in the daily dose of either drug before the start of the diet do not however appear to be justified.