Valproic acid-induced hyperammonemic encephalopathy – a potentially fatal adverse drug reaction

BACKGROUND A patient with an early diagnosed epilepsy Valproic acid is one of the most widely used antiepileptic drugs. Hyperammonemic encephalopathy is a rare, but potentially fatal, adverse drug reaction to valproic acid. CASE DESCRIPTION A patient with an early diagnosed epilepsy, treated with valproic acid, experienced an altered mental state after 10 days of treatment. Valproic acid serum levels were within limits, hepatic function tests were normal but ammonia levels were above the normal range. Valproic acid was stopped and the hyperammonemic encephalopathy was treated with lactulose 15 ml twice daily, metronidazole 250 mg four times daily and L-carnitine 1 g twice daily. DISCUSSION AND EVALUATION Monitoring liver function and ammonia levels should be recommended in patients taking valproic acid. The constraints of the pharmaceutical market had to be taken into consideration and limited the pharmacological options for this patient's treatment. CONCLUSIONS Idiosyncratic symptomatic hyperammonemic encephalopathy is completely reversible, but can induce coma and even death, if not timely detected. Clinical pharmacists can help detecting adverse drug reactions and provide evidence based information for the treatment.