Efavirenz (Sustiva(tm) ) and Saquinavir (Fortovase«) Combination: Pharmacologic Interaction

Anyone taking both efavirenz and saquinavir should know that the combination can reduce the plasma level of saquinavir by about 60%--which will likely result in underdosing of the protease inhibitor. DuPont Merck (soon to be called DuPont Pharmaceuticals), the maker of efavirenz, "strongly urges patients taking Sustiva with Fortovase to talk to their physicians about changing their regimens."
Currently efavirenz is not marketed but is available through clinical trials or through an expanded access program. The company has sent detailed information to physicians in those programs.