Introduction: Hyperammonemia is one of the rare nevertheless serious side effects associated with valproic
acid treatment. Two cases of valproic acid induced hyperammonemia are detailed in this article.
Cases: Case one describes an adult male who developed hyperammonemia after acute exposure to valproic acid as a
treatment for his bipolar disorder-manic episode. Case two developed a similar pattern of toxicity but after chronic
exposure to valproic acid. Both patients were receiving a combination of valproic acid and quetiapine.
Discussion: Measurement of the ammonium level should be considered where there is a decreased level of consciousness
in patients receiving valproic acid irrespective of the diagnosis and even after a long term exposure. A possible risk of
hyperammonemia can result from a combination of valproic acid and quetiapine, however further studies are yet needed to
confirm this hypothesis.