HIV Disease and AIDS
Managing HIV Disease: Getting the Most from Your Therapy
PIs: Protease Inhibitors
Protease inhibitors are considered a major advance in the control of HIV disease. As the name implies, they inhibit the action of a substance called protease. PIs are especially effective when used in combination with Nucleoside Reverse Transcriptase Inhibitors (NRTIs).
Drugs within this group:
- PrCRIXIVAN® (indinavir sulfate)
- PrNorvir™ (ritonavir)
- PrInvirase™ (saquinavir)
- PrViracept® (nelfinavir)
CRIXIVAN® is a trademark of Merck & Co., Inc., Merck Frosst Canada & Co., licensed user.
Norvir™ is a trademark of Abbott Laboratories Ltd.
Invirase™ is a trademark of Hoffman-La Roche Ltd.
Viracept® is a registered trademark of Agouron Pharmaceuticals Inc.
What PIs do:
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PIs go to work during one of the last and most critical stages of the HIV-copying process. They are often used in combination with NRTIs, which affect an early stage of HIV development.
- Protease is the enzyme or substance that enables HIV to spread. Like a cutting device on an assembly line, protease automatically slices long HIV strips into smaller sections. It is these shorter pieces of the virus that move on to infect additional CD4 cells.
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Protease inhibitors interfere with the protease cutting stage. In effect, PIs get in the way of the protease blade so it is unable to cut the long HIV strips into the short pieces which HIV needs to copy itself. The long strips of HIV are unable to infect additional CD4 cells unless they are cut into shorter pieces.
How PIs differ from Reverse Transcriptase Inhibitors (RTIs)
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RTIs go to work soon after HIV infects a cell. PIs act at a much later stage -- just as HIV is preparing to mount its attack against other cells.
- In most studies to date, treatments combining RTIs and a PI have been shown to be more powerful than RTIs alone in both slowing HIV reproduction and in helping to increase the numbers of infection-fighting CD4 cells.
