Drug Interactions between Mepron and naltrexone

ADJUST DOSING INTERVAL: Food, particularly high-fat food, significantly enhances the oral absorption and bioavailability of atovaquone. In 16 healthy volunteers, administration of a single 750 mg dose of atovaquone suspension following a standard breakfast (23 g fat: 610 kCal) resulted in an approximately 3.4-fold increase in the mean peak plasma concentration (Cmax) and a 2.5-fold increase in the mean area under the plasma concentration-time curve (AUC) of atovaquone compared to administration following an overnight fast. In a study consisting of 19 HIV-infected volunteers receiving atovaquone suspension 500 mg/day, Cmax and AUC of atovaquone increased by 72% and 66%, respectively, in the fed state relative to the fasting state.

MANAGEMENT: To ensure maximal oral absorption, atovaquone products (suspension, tablet, or in combination with proguanil) should be administered with a meal or milky drink, or enteral nutrition at the same time(s) each day. Because plasma atovaquone concentrations have been shown to correlate with the likelihood of successful treatment and in some cases, survival, alternative therapies may be appropriate for patients who have difficulty taking atovaquone with food.

GENERALLY AVOID: Coadministration of naltrexone with other agents known to induce hepatotoxicity may potentiate the risk of liver injury. Naltrexone, especially in larger than recommended doses (more than 50 mg/day), has been associated with hepatocellular injury, hepatitis, and elevations in liver transaminases and bilirubin. Other potential causative or contributory etiologies identified include preexisting alcoholic liver disease, hepatitis B and/or C infection, and concomitant usage of other hepatotoxic drugs.

MANAGEMENT: The use of naltrexone with other potentially hepatotoxic agents should be avoided whenever possible (e.g., acetaminophen; alcohol; androgens and anabolic steroids; antituberculous agents; azole antifungal agents; ACE inhibitors; cyclosporine (high dosages); disulfiram; endothelin receptor antagonists; interferons; ketolide and macrolide antibiotics; kinase inhibitors; minocycline; nonsteroidal anti-inflammatory agents; nucleoside reverse transcriptase inhibitors; proteasome inhibitors; retinoids; sulfonamides; tamoxifen; thiazolidinediones; tolvaptan; vincristine; zileuton; anticonvulsants such as carbamazepine, hydantoins, felbamate, and valproic acid; lipid-lowering medications such as fenofibrate, lomitapide, mipomersen, niacin, and statins; herbals and nutritional supplements such as black cohosh, chaparral, comfrey, DHEA, kava, pennyroyal oil, and red yeast rice). Patients should be advised to seek medical attention if they experience potential signs and symptoms of hepatotoxicity such as fever, rash, itching, anorexia, nausea, vomiting, fatigue, malaise, right upper quadrant pain, dark urine, pale stools, and jaundice. Periodic monitoring of hepatic function is advisable.