ritonavir, Norvir (cont.)

Pharmacy Author:
Medical and Pharmacy Editor:

Ritonavir decreases the concentration of meperidine (Demerol) and increases the buildup of meperidine's toxic breakdown product in the body. Therefore, ritonavir reduces the beneficial effect of meperidine while increasing its side effects.

Ritonavir may increase the blood concentration of lovastatin (Mevacor), simvastatin (Zocor), and atorvastatin (Lipitor). This may result in increased occurrence of myopathy (muscle pain) or rhabdomyolysis (muscle breakdown). Lovastatin and simvastatin should not be combined with ritonavir.

St. John's wort and rifampin (Rifadin) decrease the concentration of ritonavir in the body and this could reduce the effectiveness of ritonavir.

Clarithromycin (Biaxin), ketoconazole (Nizoral), fluconazole (Diflucan) and fluoxetine (Prozac) may increase blood concentrations of ritonavir and result in increased side effects from ritonavir.

Ritonavir increases blood levels of sildenafil (Revatio) and the risk of side effects such as low blood pressure, prolonged erection, and fainting. Both drugs should not be combined.

PREGNANCY: Use of ritonavir during pregnancy has not been adequately evaluated. To monitor outcomes of pregnant women that received ritonavir, an Antiretroviral Pregnancy Registry has been established. Physicians are encouraged to register patients by calling 1-800-258-4263.

NURSING MOTHERS: It is not known whether ritonavir is secreted in breast milk. Nevertheless, HIV-infected mothers should not breast-feed because of the potential risk of transmitting HIV to an infant that is not infected.

SIDE EFFECTS: The most serious side effects are liver failure, inflammation of the pancreas (pancreatitis), heart block, and severe allergic reactions. Ritonavir also may elevate blood glucose resulting in new onset diabetes. Fat redistribution, elevated triglycerides, and elevated cholesterol levels also occur. Patients with hemophilia may experience spontaneous bleeding. Immune reconstitution syndrome which is an inflammatory response to infection may occur in patients treated with combination antiretroviral therapy. Other side effects include diarrhea, nausea and vomiting, taste disturbance, abnormal skin sensations (burning, prickling and tingling), headache, weakness, and insomnia (difficulty sleeping).

Reference: FDA Prescribing Information


Last Editorial Review: 9/10/2012



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