ritonavir, Norvir (cont.)

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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.

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