Valproic acid occasionally has a hepatotoxic effect which has been lethal in isolated cases. Children with forms of epilepsy that are difficult to treat, with advanced neurological disease, and who are treated with other antiepileptic agents, are particularly endangered. This is an 'idiopathic' reaction which normally occurs in the first six months of treatment. Encephalopathies due to increased ammonia levels and pancreatitis are very rare.

About a quarter of all the treated subjects experience side-effects, particularly of gastrointestinal nature (nausea, vomiting, gastric pain, diarrhea or constipation). An asymptomatic increase of transaminases, weight gain, alopecia, tremor, fatigue and headaches are not uncommon. Hematologic anomalies (especially thrombocytopenia), skin rashes and hirsutism are rare.

Valproic Acid: Interactions

As an enzyme inhibitor, valproic acid can reinforce the plasma levels and the effects of other antiepileptic agents. Salicylates increase and enzyme inducers reduce the valproate effect.

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