for Veterans and the Public
Protease Inhibitors (PIs)
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.
There are nine PIs (most of them are older medicines and are not used currently):
- Aptivus® (tipranavir)
- Crixivan® (indinavir)
- Invirase® (saquinavir)
- Kaletra® (lopinavir + ritonavir combined in one tablet)
- Lexiva® (fosamprenavir)
- Norvir® (ritonavir)
- Reyataz® (atazanavir)
- Viracept® (nelfinavir)
Many PIs are recommended or approved for use only with another drug that "boosts" their effect. One of these is low-dose Norvir®, the other is a non-HIV drug called Tybost® (cobicistat).
There are three fixed-dose combination tablets that include a "booster" plus a PI:
- Evotaz® (Reyataz® + Tybost®)
- Prezcobix® (Prezista® + Tybost®)
- Kaletra® (lopinavir + Norvir®)