Suspected bromide intoxication due to ketogenic diet?

Introduction: Bromide is the oldest antiepileptic drug acting by increasing GABA induced cerebral inhibition. It is licensed for primary or secondary generalized tonic-clonic seizures and is especially useful for infantile idiopathic generalized epilepsy syndromes. Favored drug combination is with valproic acid. Usual side effects are dose related drowsiness and provoked seizures by sudden reduction. Chronic side effect is bromism with mainly dermatological problems.

Ketogenic diet is a high-fat, low-carbohydrate and adaequate-protein diet. It imitates metabolic state of fasting. Combination of ketogenic diet with bromide is a rare antiepileptic therapy regime, little is known about possible interactions.

Case report: We present a 6 year old boy with Dravet syndrome treated with potassium bromide (50mg/kg body weight- plasma level 1200mg/L – therapeutic level: 750–2000mg/L). After starting ketogenic diet plasma levels of bomide increased up to 3800mg/L although dosage was not increased. Clinically there were no signs of side effects. As reduction of bromide dosage resulted in increased seizure frequency, bromide dosage was again increased up to 50mg/kg body weight. Since 8 months the patient has no side effects, but plasma levels of bromide measured repeatedly are still high suggesting intoxication.

Conclusion: Little is known about interaction of antiepileptic drugs and ketogenic diet. Bromide interacts with ketogenic diet resulting in higher plasma level of bromide. In this case no clinical signs of bromide intoxication were observed.

Keywords: ketogenic diet, Dravet syndrome, Bromide