Protease Inhibitors

A category of prescription medications called Protease Inhibitors (PIs) are used to prevent or treat AIDS by inhibiting viral reproduction. The HIV virus replicates itself by causing healthy cells to produce certain proteins and enzymes. Part of the process uses an enzyme called protease as a key tool to shorten normally long protein chains. PI’s prevent protease from participating in the making of new virus copies, thus interrupting the creation of more infected cells. A Protease Inhibitor throws a "monkey wrench" into one segment of the HIV assembly line. Thus the PI’s goal is to slow down the spread of the HIV virus by reducing its replication.

Protease inhibitors are often used in combination with drugs called reverse transcriptase inhibitors, which target another key enzyme called reverse transcriptase. This is the enzyme HIV employs to insert itself into the nucleus of an infected cell. The operations of protease and reverse transcriptase occur at different points of the virus' replication, so the drugs designed to inhibit these two enzymes can be used together to slow down the virus at two different critical reproductive steps.

The combination of Protease Inhibitors with other anti-HIV drugs such as reverse transcriptase inhibitors can prevent many opportunistic infections and help to extend an infected person's life. This combination of potent medications is called Highly Active Antiretroviral Therapy (HAART).

Testing of PIs in laboratory settings but not yet in humans is also occurring, to see if they can be used as anti-anti-cancer and anti-Hepatitis C agents. Development of the drugs began in the 1990s, with FDA approval for marketing starting in 1995. Therefore most of these medications are under patent protection for another ten or more years.

PIs are also referred to as antiretroviral Protease Inhibitors. Additional names for these medications include:
• Agenerase (Amprenavir)
• Aptivus (Tipranavir, Tipranavir Disodium)
• Crixivan (Indinavir)
• Invirase (Saquinavir, the first PI approved by the FDA)
• Kaletra (Lopinavir)
• Lexiva (Fosamprenavir)
• Norvir (Ritonavir)
• Prezista (Darunavir)
• Reyataz (Atazanavir)
• Viracept (Nelfinavir)

If your doctor prescribes a Protease Inhibitor, it is essential to follow dosing instructions carefully and to maintain a consistent schedule of taking the medication. It is usually taken at least two times a day, but your doctor or pharmacist can answer any questions you may have about dosage and side effects. You should ask whether the drug is to be taken on an empty or full stomach. A thorough medical check-up prior to starting on these drugs is strongly suggested.

The benefits of Protease Inhibitors include a reduction of the amount of HIV virus in the blood, improvement in CD4 cell counts, and general improvement in well-being and activity level. Like any medication taken for the long term, they may lose effectiveness over time.

Many people are able to tolerate the drugs well, but others have serious and significant side effects. These can include high blood sugar and diabetes. Watch for symptoms such as increased urination, excessive thirst and hunger, weight loss, fatigue, and itching occurring within the first two or three months of using a protease inhibitor.

Another serious side effect is lipodystrophy, or the development of a high level of blood fat such as cholesterol and triglycerides. High blood fat can lead to fatigue and loss of well-being, in addition to heart attacks, pancreatitis, and body changes such as a swollen belly, enlarged breasts, and muscle loss. Your doctor should regularly check your cholesterol and triglyceride levels while you are taking PIs.

A less common side effect is liver toxicity and the development of problems with liver function or infections such as hepatitis. Your doctor should do regular blood tests to check the health of your liver.

Remember that it is crucial to adhere to the proper dosage and schedule for these medications and to follow instructions carefully. Be sure to discuss any side effects or other concerns you may have with your doctor or pharmacist.

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