Valproic Acid–Induced Eosinophilic Pleural Effusion: A Case Report and Review of the Literature

Abstract

To report a case of valproic acid-induced eosinophilic pleural effusion and to review the existing literature. A 25-year-old African-American man receiving valproic acid, 250 mg/d, had a moderate-sized right pleural effusion. Pleural fluid analysis revealed 75% eosinophils. The patient had no evidence of parasitic infection, hemothorax, or pneumothorax. One month after valproic acid was discontinued, there was no evidence of a pleural effusion by both chest radiography and thoracic ultrasonography. Valproic acid-induced pleural effusions have been reported in the medical literature in 5 case reports. Pleural fluid eosinophilia is almost always related to pneumothorax, hemothorax, parasitic infection, or drug toxicity; therefore, when the first 3 causes have been eliminated, a drug should be suspected. Only a few medications are known to cause pleural fluid eosinophilia, one being valproic acid. The Naranjo probability scale rated this adverse reaction as probably drug-related. In all 6 patients discussed in this review, the pleural effusions resolved after discontinuation of the valproic acid. None of these patients had associated pulmonary infiltrates. Valproic acid eosinophilia may be associated with peripheral blood eosinophilia. Valproic acid should be added to the list of medications that can cause an eosinophilic pleural effusion.