Saquinavir Mesylate (Invirase)

• Type of Drug: Protease inhibitor.
• Prescribed for: Advanced HIV infection.

Saquinavir Mesylate (Invirase) General Information

Saquinavir Is the first of a new class of anti-HIV drugs that works by a unique method of action: protease inhibition. It ii always used together with one of the older nucleoside drugs, such as AZT, ddl, or ddC. When the HIV virus attacks a cell, it must be converted into viral DNA. The older drugs work to prevent this step and are also known as reverse transcriptase inhibitors. Saquinavir works at the end of the process of HIV reproduction, when proteins are cut into strands of exactly the correct size. The protein is cut by an enzyme known as protease, and Saquinavir prevents the mature virus from being formed through prevention or inhibition of this cutting process. Improperly or uncut proteins are inactive.

Studies have shown that combining the two types of drugs is more effective than taking either one alone (as judged by CD4 cell levels), but there is no conclusive evidence that taking Saquinavir slows disease progression or improves survival.

Saquinavir Mesylate (Invirase) Cautions and Warnings

Do not take this drug if you are sensitive or allergic to the drug.

If a serious toxicity occurs while taking Saquinavir, the drug should be stopped so that your doctor can determine the reason for the toxic event or until it resolves. Then, treatment can be restarted.
Caution must be exercised if you have moderate to severe liver disease.

There is a chance that strains of the HIV virus may become resistant to Saquinavir and that other protease inhibitors under development will also be rendered ineffective, but this effect will have to be studied as other protease inhibitor drugs become available.

Possible Side Effects

Most Saquinavir side effects are mild.

• Most common: diarrhea, nausea, and abdominal discomfort. When Saquinavir is taken together with one of the older antiretroviral drugs, other side effects become more prominent, including weakness, muscle pain, and mouth ulcers.
• Less common: upset stomach, abdominal pain, mouth ulcers, headache, tingling in the hands or feet, numbness in the hands or feet, dizziness, nerve damage, appetite disturbances, and rash.
• Other: side effects of Saquinavir can affect almost any body system. Report anything unusual to your doctor.

Saquinavir Mesylate (Invirase) Drug Interactions

• Rifampin and Rifabutin increase the rate at which Saquinavir is broken down in the liver and drastically reduce the amount of Saquinavir (by 80 percent and 40 percent, respectively) in the blood. Do not mix these drugs. Other drugs that can reduce Saquinavir blood levels are Phenobarbital, Phenytoin, Carbamazepine, and Dexamethasone.
• Blood levels of Saquinavir may be elevated by Terfenidine, Astemizole, Ketoconazole, Itraconazole, calcium channel blockers, Clindamycin, Dapsone, Quinidine, and Triazolam. Taking these drugs with Saquinavir may lead to drug side effects.

Food Interactions

Take Saquinavir within 2 hours of a full meal. The amount of Saquinavir absorbed into the blood is vastly reduced when it is taken on an empty stomach. You will not get any antiviral activity unless it is taken with food.

Usual Dose

Adult (age 16 and older): 600 mg 3 times a day within 2 hours of a full meal.
Child (under age 16): not recommended.

Saquinavir Mesylate (Invirase) Overdosage

No acute problems developed in one person who took 8000 mg of Saquinavir at once after the victim was made to vomit. In a study of people taking up to 7200 mg a day for 25 weeks, no unusual effects were seen. Call your local poison center’ for more information. Overdose victims should be taken to a hospital emergency room for treatment. ALWAYS bring the medicine bottle with you.

Special Information

Saquinavir does not cure HIV infection or AIDS. You may develop opportunistic infections or other illnesses associated with advanced HIV disease. Saquinavir has not been shown to reduce the possibility of transmitting the HIV virus to another person. The long-term effects of this drug are not known.

Saquinavir should be taken at the same time as you take your nucleoside antiviral drug. If you forget a dose of Saquinavir, take it as soon as you remember. If it is almost time for your next dose, skip the forgotten dose and continue with your regular schedule. Do not take a double dose of Saquinavir.

Saquinavir Mesylate (Invirase) Special Populations

Pregnancy/Breast-feeding
Animal studies with pregnant animals have shown no negative effects of Saquinavir on the developing fetus. There are no reports of pregnant women receiving this drug, but it should be used with caution if you are pregnant.
It is not known if this drug passes into breast milk. Nursing mothers who must take Saquinavir should bottle-feed their babies.

Seniors
Older adults can take this drug without special precaution.