The United States Food and Drug Administration (US FDA) has informed healthcare professionals and patients in the US that drug interactions between the hepatitis C virus (HCV) protease inhibitor boceprevir (Victrelis®) and certain ritonavir-boosted human immunodeficiency virus (HIV) protease inhibitors (atazanavir, lopinavir, darunavir) can potentially reduce the effectiveness of these medicines when they are used together.

A pharmacokinetic study in healthy volunteers (n=39) found that taking boceprevir with ritonavir in combination with atazanavir or darunavir, or with Kaletra® (lopinavir/ritonavir) reduced the blood levels of the HIV medicines and boceprevir in the body. The FDA will be updating the boceprevir drug label to include information about these drug interactions and has advised:

• Healthcare professionals who have started patients infected with both chronic HCV and HIV on boceprevir and antiretroviral therapy containing a ritonavir-boosted protease inhibitor should closely monitor patients for HCV treatment response and for potential HCV and HIV virologic rebound.

• Healthcare professionals and patients are encouraged to report adverse events or side effects related to the use of these products to the FDA's MedWatch Safety Information and Adverse Event Reporting Program

• Patients should not stop taking any of their medicines without talking to their healthcare professional. Patients should contact their healthcare professional if they have any questions or concerns.

Boceprevir was launched in the UK in August 2011 for the treatment of chronic hepatitis C genotype 1, in combination with peginterferon alfa and ribavirin in patients with previously treated or untreated disease.

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