Confusion, a Rather Serious Adverse Drug Reaction with Valproic Acid: A Review of the French Pharmacovigilance Database

Introduction: Confusion is an adverse drug reaction frequently observed with valproic acid. Some case reports are published in the literature but no systematic study from a sample of patients has been published. We performed this study in order to describe the main characteristics of this adverse drug reaction. Methods: Using the French Pharmacovigilance database, we selected the cases of confusion reported since 1985 with valproic acid. Results: 272 cases of confusion were reported with valproic acid: 153 women and 119 men. Confusion mostly occurred during the two first weeks following valproic acid exposure (39.7%). It was "serious" for almost 2/3 of the patients (62.5%) and its outcome favourable in most of the cases (82%). The occurrence of this ADR was more frequent in patients aged between 61 and 80 years. Conclusion: This work shows that confusion with valproic acid is a serious, rather frequent but reversible adverse drug reaction. It occurs especially in older patients and during the first two weeks of treatment.