Drug interactions between Depakote and Zyprexa

MONITOR: Concurrent use of olanzapine and valproic acid may potentiate the risk of hepatotoxicity. The exact mechanism of interaction is unknown. In a retrospective study of 52 children, combined treatment with olanzapine and divalproex was associated with more frequent elevations of hepatic enzymes than either agent alone, and mean and peak hepatic enzyme levels during the observed course of treatment were also higher. All 12 patients who received combined treatment had at least one peak enzyme elevation above the normal range, versus 10 of 17 who received olanzapine alone and 6 of 23 who received divalproex alone. With the exception of 2 patients who required discontinuation of combination treatment (due to development of pancreatitis in one and steatohepatitis in the other), the observed peak and mean enzyme levels were less than 3 times the upper limit of normal (ULN) and were asymptomatic. The long-term significance of these findings is unknown.

MANAGEMENT: The authors of the study recommend monitoring liver function tests every 3 to 4 months during the first year of treatment with either olanzapine or valproic acid, at least in pediatric patients. If no elevations of liver enzymes or marked weight gain occur after one year, a decrease in frequency of monitoring to every 6 months can be considered. Patients should be advised to notify their physician if they experience signs and symptoms of hepatotoxicity such as fever, rash, anorexia, nausea, vomiting, fatigue, right upper quadrant pain, dark urine, and jaundice.