Merck & Co.'s hepatitis C virus (HCV) treatment Victrelis (boceprevir) considerably lessens the effectiveness of some widely used HIV drugs, U.S. regulators and Merck recently announced.
"These drug interactions may be clinically significant for patients infected with both chronic hepatitis C virus and HIV by potentially reducing the effectiveness of these medicines when co-administered," Merck said in a Feb. 6 letter to health care professionals.
The drug interactions were seen in a study of healthy volunteers who took Victrelis, which is an HCV protease inhibitor, and certain HIV protease inhibitors boosted by Norvir (ritonavir). Victrelis reduced the concentrations in the blood of Reyataz (atazanavir), Prezista (darunavir), and Kaletra (lopinavir/ritonavir) an average of 49 percent, 59 percent, and 43 percent, respectively. Levels of Victrelis itself were reduced by 45 percent among those taking it with Kaletra, and 32 percent among those taking it in combination with Norvir and Prezista.
Patients should not stop taking any of their medicines without talking to health care professionals. Drug interactions have previously been found between Victrelis and the non-nucleoside reverse transcriptase inhibitor Sustiva (efavirenz). Merck said it is conducting drug-interaction studies for other HIV drugs, including the NNRTI Intelence (etravirine) and the integrase inhibitor Isentress (raltegravir).
For more information, visit: www.fda.gov/Drugs/DrugSafety/ucm291119.htm.