What is saquinavir? How does it work (mechanism of action)?

Saquinavir is an oral medication that is used for treating infections with the human immunodeficiency virus (HIV). It is in a class of drugs called protease inhibitors which also includes indinavir (Crixivan), nelfinavir (Viracept) and ritonavir (Norvir). During infection with HIV, the HIV virus multiplies within the body's cells. Viruses are released from the cells and spread throughout the body where they infect other cells. In this manner, HIV infection is perpetuated among new cells that the body produces continually. During the production of the viruses, new proteins are made. Some of the proteins are structural proteins, that, is, proteins that form the body of the virus. Other proteins are enzymes which manufacture DNA and other components for the new viruses. Protease is the enzyme that forms the new structural proteins and enzymes. Saquinavir blocks the activity of protease and results in the formation of defective viruses that are unable to infect the body's cells. As a result, the number of viruses in the body (the viral load) decreases. Nevertheless, saquinavir does not prevent the transmission of HIV among individuals, and it does not cure HIV infections or AIDS.

  • Saquinavir was approved by the FDA in December 1995.
  • Retorvir is the brand name for saquinavir.
  • Saquinavir is not available in generic form.
  • You need a prescription for Saquinavir.

What is the dosage for saquinavir?

The recommended dose of Invirase for adults is 600 mg three times daily. Invirase should be administered within 2 hours of a meal.

Which drugs or supplements interact with saquinavir?

Saquinavir interacts with many drugs. Some of the important interactions are mentioned below. Viewers should consult their health care provider before combining any drugs with saquinavir.

Saquinavir should not be used together with triazolam (Halcion), midazolam (Versed), sildenafil (Viagra) and ergotamine derivatives (for example, Ergostat) because saquinavir increases the concentration of these drugs in the body and this could cause serious side effects.

Saquinavir also may inhibit the break-down of the cholesterol-lowering drugs lovastatin (Mevacor), simvastatin (Zocor), atorvastatin (Lipitor) and cerivastatin (Baycol). Combining saquinavir with these drugs may increase the occurrence of muscle breakdown (rhabdomyolysis) which is seen when these drugs accumulate in the body.

Clarithromycin (Biaxin) and ketoconazole (Nizoral) may increase blood concentrations of saquinavir and cause increased severity or frequency of side effects from saquinavir. Saquinavir also increases the concentration of clarithromycin.

Rifampin (Rifadin) and rifabutin (Mycobutin) decrease blood concentrations of saquinavir and therefore could decrease the effectiveness of saquinavir.

The combination of saquinavir and ritonavir should not be combined with rifampin due to the risk of severe liver damage.

When digoxin is taken by patients receiving saquinavir (Invirase) with ritonavir (Norvir), the amount of digoxin (Lanoxin) in the body can increase by 50%, possibly leading to side effects such as potentially fatal rhythm disturbances, nausea, vomiting, and diarrhea, blurred or yellow vision; headache; weakness; dizziness; apathy; confusion; and mental disturbances such as anxiety, depression, delirium, and hallucinations.


A Timeline of the HIV/AIDS Pandemic See Slideshow

Is saquinavir safe to take if you are pregnant or breastfeeding?

  • Use of saquinavir during pregnancy has not been adequately evaluated.
  • It is not known whether saquinavir is secreted in breast milk. Nevertheless, HIV-infected mothers should not breast-feed because of the potential risk of transmitting HIV to an infant that is not infected.

What else should you know about saquinavir?

What preparations of saquinavir are available?

Tablets: 500 mg; Capsules: 200 mg

How should I keep saquinavir stored?

Store Invirase capsules at room temperature, 15 C - 30 C (59 F - 86 F).


Saquinavir (Invirase) is an oral medication that is used for treating infections with the human immunodeficiency virus (HIV). Side effects of saquinavir include changes in the shape or location of body fat, feeling tired, nausea, diarrhea, and stomach pain. Serious life threatening side effects include signs of an allergic reaction, cough with mucus, chest pain, heart problems, high blood sugar, and liver problems. Signs and symptoms of a new infection include cold sores, fever, night sweats, wheezing, and cough. Talk to your doctor about any side effects that you are concerned about. Drug interactions are many for saquinavir. Use of saquinavir has not been adequately evaluated. Saquinavir is secreted in breast milk so mothers who are breastfeeding should not be taken due to the potential risk of transmitted HIV to an infant not infected.

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FDA Prescribing Information.