Valproate-induced Hyperammonaemia in a Bipolar Disorder Patient: A Case Report

Valproate is a widely used mood stabiliser in neurology and psychiatric practice. It can cause rare but serious adverse effects, including hyperammonaemia. Hereby, the authors present a case report of 40-year-old married male diagnosed with bipolar affective disorder, who presented with manic symptoms and subsequently developed hyperammonaemia after the initiation of Sodium Valproate. Despite normal liver function and no history of substance use, the patient exhibited excessive drowsiness and constipation five days after increasing the valproate dosage to 1500 mg/day. Serum ammonia levels were significantly elevated, prompting the cessation of all psychiatric medications and the initiation of lactulose treatment. Over six days, ammonia levels normalised, revealing the underlying manic symptoms. The patient was transitioned to Lithium for mood stabilisation while Valproate was not reintroduced. The case highlights the potential for hyperammonaemia in patients receiving valproate, even in the absence of liver dysfunction. The mechanisms behind this adverse effect may include Carnitine depletion and toxic metabolite accumulation from valproate metabolism. The report underscores the importance of vigilance in monitoring for hyperammonaemia, particularly in patients receiving rapid dose escalations of valproate. Limitations of the report include the absence of serum Valproate levels at the time of hyperammonaemia, which would have aided in understanding the dose-response relationship. It also highlights the need for early detection of hyperammonaemia and appropriate management.