[Valproic acid and protein supplements: possible clinically relevant drug interaction]

Introduction: valproic acid (VPA) is a drug with narrow therapeutic index (50-100 µg/mL) with a high pharmacokinetic variability due to plasma protein binding saturation (PPBU). Case report: we present a clinical case of a 60-year-old patient under treatment with VPA, whose plasma VPA concentrations were analyzed and a decrease in these concentrations was detected when administrated with protein supplement. When the intake was spaced out, VPA serum concentrations returned to the therapeutic range. Discussion: administration with food does not appear to be important according to the majority of the literature available to date. However, this case seems to show that protein supplements can interact with VPA and it is important to space out the intake between them to minimize variation in plasma concentrations.