There are currently five drugs approved for use in this class. PIs work by preventing protease from cutting long chains of proteins into shorter ones necessary for HIV to make new copies of itself. As a result, defective copies of HIV are made that are unable to infect other cells or reproduce. PIs work at a completely different stage of the HIV life cycle than the other two classes of antiretroviral drugs. This is one of the advantages of having PIs in a combination therapy.
Viracept (aka: nelfinavir)
Commonly known as Viracept this is the most commonly prescribed protease inhibitor today. Viracept is usually taken as three 250-mg tablets three times a day. Late last year, the FDA approved twice a day dosing at 1,250 mg per dose. Talk to your doctor if you want to change how often you take Viracept. It is recommended that this drug be taken with meals. The most common side effect associated with Viracept is severe diarrhea, and use of over-the-counter drugs to control the diarrhea is often required. Other possible side effects include headache and nausea. Viramune can have adverse drug interactions with various antihistamines, sedatives, and anti-fungal medications, so be sure your doctor and pharmacist know all of the medications you are taking when on Viracept.
Crixivan (aka: indinavir)
Commonly called Crixivan (or "crix" for short), this drug is usually taken as four 200-mg tablets three times a day, or two 400-mg tablets three times a day. Food restriction is to take on an empty stomach one hour before eating or two hours after eating. The most common side effect of Crixivan is kidney stones. You can reduce the risk of kidney stones by drinking at least eight glasses of water every day. Other possible side effects include anemia, fatigue, upset stomach, and rash. Crixivan capsules contain lactose, so if you are lactose intolerant this may increase stomach problems. Drug interactions can occur with several antihistamines, sedatives, and anti-fungal drugs.
Fortovase (aka: saquinavir)
Commonly called Fortovase, this drug is usually taken as six 200-mg tablets three times a day. Should be taken with food, or within two hours of a full meal. Common side effects are diarrhea, stomach pain, and nausea. Drug interactions can occur with several antihistamines, sedatives, and anti-fungals. Capsules can normally be stored at room temperature, but should be refrigerated in hot climates. (Fortovase is a stronger and improved version of the drug "Invirase.")
Norvir (aka: ritonavir)
Commonly called Norvir, this drug is usually taken as six 100-mg tablets twice a day. Should be taken with a full meal. Common side effects are weakness, diarrhea, peripheral neuropathy, and changes in taste. Lead-in dosing is recommended to help reduce side effects -- consult with your doctor or pharmacist. Low-dose Norvir is commonly being used in combination with other PIs to help boost the drug levels in the blood making them more effective.
Amprenavir (aka: agenerase)
Commonly called Amprenavir, this drug is usually taken as eight 150-mg tablets twice a day. Amprenavir can be taken with or without food, but high-fat foods should be avoided. Common side effects are diarrhea, nausea, rash, and numbness around the mouth. The usual PI drug interactions with some antihistamines, sedatives, and anti-fungals may occur. Amprenavir is reported to work better with the NRTI called abacavir.