Interactions depend on the macrolide antibiotic you take. Do not co-administer Norvir with an antibiotic without consulting a medical specialist.
Norvir is a well-known therapy prescribed to individuals diagnosed with HIV/AIDS to reduce the amount of virus in their body and boost CD4+ cell count. It’s a highly potent antiretroviral medicine used along with other ARV medications (i.e. protease inhibitors) to effectively treat HIV/AIDS [1].
Norvir has an active substance called ritonavir, which is a protease inhibitor. With its mechanism of action, this medicine inhibits an HIV enzyme called protease, which is used by the virus to multiply in the body.
Ritonavir can also be used as a booster, helping to boost the processes and absorption of other ARV protease inhibitors [2].
Various antibiotics interact with ritonavir at different levels. Some antibiotics can be used together without any interaction, some require dose adjustment for it to effectively work, while others cannot be coadministered with Norvir.
Most macrolides are prescribed to HIV-infected individuals to lower the HIV-related morbidity and mortality. Macrolides such as co-trimoxazole or a combination of azithromycin and atovaquone are very effective in preventing serious bacterial infections in HIV-positive patients. In fact, co-trimoxazole antibiotic is a potent prophylactic acting against PCP pneumonia in HIV-infected individuals.
However, some antibiotics can cause potentially serious negative effects such as induced hepatic injury with hypersensitivity-like reactions when administered. This can be accompanied by symptoms such as rash, fever, and eosinophilia. When administering this substance with other ARV meds, it’s highly recommended to assess the patient’s health including testing blood for the presence of liver problems [3].
Since there is a limited clinical test on antibiotics and ARV meds, only some of the macrolides such as clarithromycin, metronidazole, rifampin, and rifabutin have been studied.
Co-administering clarithromycin with ritonavir has no significant change on ritonavir AUC, but causes an increase of Cmax by 15%. In contrast, the same combination increased clarithromycin effects. Clarithromycin AUC, Cmax, and Cmin are increased by 77%, 31%, and 182% respectively. Nonetheless, no dose adjustment is necessary.
Metronidazole with ritonavir combination is not recommended.
Combined with rifabutin, there is an increase of 400% in levels of rifabutin AUC and a 250% increase in Cmax. In this case, if the combination is necessary, lower rifabutin to 150 mg QOD or administer 300 mg 3 times/week.
With rifampin, ritonavir AUC is decreased by 35% and Cmax decreased by 25%. As it decreases the Norvir effects, do not co-administer [4].
There might be other antibiotic interactions. Check with your medical specialist concerning all the antibiotics you are using prior to mixing with ARV drugs.