Hyperammonemia and carnitine deficiency with concomitant encephalopathy have been reported to result from valproic acid administration (Coulter DL, J Child Neurol 1991Jan; 6(1); 7-14 and Mock, CM, et al, Am J Health Syst Pharm, 2012 Jan; 69(1):35-9). Although there have been numerous publications regarding this adverse event in the neurology literature, there have been very few reports published in the psychiatric literature. The reported incidence of hyperammonemia in children treated with valproate is 19%. It is important that prescribers be aware of the risk of valproic acid induced hyperammonemic encephalopathy, as well as its diagnosis and management.

The current study explores the feasibility of reversing Valproate Induced Hyperammonemic Encephalopathy (VHE) by discontinuing valproic acid and normalizing the carnitine level via L-carnitine supplementation.

Three males (ages 10-16 years), are reported with 12 - 24 month histories of cognitive decline during treatment for “Bipolar Disorder of Childhood” with valproate. All were referred with multi-year histories of explosive/impulsive aggression and multiple unsuccessful psychopharmacological regimes. The one consistent medication throughout treatment was sodium valproate. The subjects received serial neuropsychological testing, complex EEG, MRI, valproic acid, carnitine, and ammonia blood levels. Oxcarbazepine titrated to 30-50 mg/kg/day was substituted for valproate after initial testing was completed. Normative reference laboratory levels were as follows: (1) ammonia (reference interval 15-45 mcg/dl), (2) total carnitine (reference interval 34-77 nmol/ml), and (3) valproic acid (reference interval 50-125 mcg/ml).

Case Study 1: Male, 10 years old, ammonia 78 mcg/dl; carnitine 17 nmol/ml; valproic acid 92 mcg/ml. IQ 79 (compared to 105 one year earlier); MRI cerebral atrophy; EEG - left temporal aberrancies.

Case Study 2: Male, 12 years old, ammonia 76 mcg/dL; carnitine 14 nmol/ml; valproic acid 104 mcg/ml. IQ 89 (compared to 109); MRI normal; EEG - left temporal aberrancies.

Case Study 3: Male, 16 years old, ammonia 72 mcg/dl; carnitine 24 nmol/ml; valproic acid 125 mcg/ml. IQ 45 (compared to 65); MRI normal; EEG - left temporal aberrancies.

In all three subjects, after valproate was removed (oxcarbazepine substituted) and supplemental L-carnitine added, ammonia and total carnitine levels normalized. At one year follow up, IQ’s returned to previous baselines, and MRI atrophy (Case 1) normalized. EEG aberrancies were unchanged. Patients were mood and behaviorally stable on oxcarbazepine.

Evidence of cognitive decline while on valproate warrants ammonia and carnitine level testing. If these levels are abnormal, VHE should be diagnosed and valproate should be removed as rapidly as feasible; L-carnitine supplementation (the lesser of 100 mg/kg/day or 2 grams/day) should be implemented to normalize the carnitine level.

No funding.