The European Commission has approved Boehringer Ingelheim's protease inhibitor Aptivus to be used in combination with Abbott Laboratories' Norvir for HIV/AIDS patients who have become resistant to other drugs, Boehringer said on Wednesday, Reuters reports (Reuters, 10/26). The approved dosage of Aptivus, which is known generically as tipranavir, is 500 milligrams in combination with 200 milligrams of Norvir, which is known generically as ritonavir, taken twice daily (Boehringer release, 10/26). Protease inhibitors work by blocking the action of an enzyme that cuts HIV proteins into the shorter sections that the virus needs to replicate. FDA in June gave accelerated approval for Aptivus to be used in combination with Norvir (Kaiser Daily HIV/AIDS Report, 6/23). Aptivus also has been approved for use in Mexico and Switzerland and is under review by other regulatory agencies, AFX/Forbes reports (AFX/Forbes, 10/26).