for Veterans and the Public

The third group of drugs is the protease (pronounced "pro-tee-ase") inhibitors (PIs).

Once HIV has infected a cell and made copies of itself, it uses an enzyme called protease to process itself correctly so it can be released from the cell to infect other cells. These medicines work by blocking protease.

Nine PIs are available:

• Aptivus^® (tipranavir)
• Crixivan^® (indinavir)
• Invirase^® (saquinavir)
• Kaletra^® (lopinavir + ritonavir combined in one tablet)
• Lexiva^® (fosamprenavir)
• Norvir^® (ritonavir)
• Prezista^®(darunavir)
• Reyataz^® (atazanavir)
• Viracept^® (nelfinavir)

Note: Many PIs are recommended or approved for use only with low-dose Norvir, which "boosts" their effect.