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Ann Pharmacother. 2006 Jan;40(1):147-50. Epub 2005 Dec 20.

Possible interaction between lopinavir/ritonavir and valproic Acid exacerbates bipolar disorder.

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  • 1Faculty of Pharmacy, University of Montréal, Montréal, Québec, Canada. nancy.sheehan@umontreal.ca

Abstract

OBJECTIVE:

To describe a case of exacerbated mania potentially related to an interaction between lopinavir/ritonavir and valproic acid (VPA) and propose a mechanism of action for this interaction.

CASE SUMMARY:

A 30-year-old man with bipolar disorder and HIV initiated treatment with lopinavir/ritonavir, zidovudine, and lamivudine. Prior to beginning therapy with these antiretrovirals, he was receiving VPA 250 mg 3 times daily, with his most recent VPA concentration measured at 495 micromol/L. Twenty-one days after starting antiretroviral treatment, he became increasingly manic. His VPA concentration at admission was 238 micromol/L, a 48% decrease. The daily VPA dose was increased to 1500 mg, and olanzapine was introduced. The VPA concentration following this dose escalation was 392 micromol/L, and the patient improved clinically.

DISCUSSION:

Fifty percent of VPA is metabolized by glucuronidation, 40% undergoes mitochondrial beta-oxidation, and less than 10% is eliminated by the cytochrome P450 isoenzymes. Ritonavir can induce glucuronidation of several medications including ethinyl estradiol, levothyroxine, and lamotrigine. We believe that ritonavir-mediated induction of VPA glucuronidation resulted in a decrease in VPA concentrations and efficacy. An objective causality assessment suggested that the increased mania was probably related to the decrease in VPA concentration and that a possible interaction exists between lopinavir/ritonavir and VPA.

CONCLUSIONS:

A potential interaction exists between VPA and all ritonavir-boosted antiretroviral regimens. Clinicians should monitor patients closely for a decreased VPA effect when these medications are given concomitantly.

PMID:
16368918
[PubMed - indexed for MEDLINE]
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