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Other Names: NFV, Viracept®
Manufacturer: Agouron, Inc.

What is it?

Nelfinavir belongs to a group of drugs known as protease inhibitors. It is used to treat HIV, a retrovirus. Retroviruses use the genetic material in the body’s cells to produce more virus which can infect other cells.

How does it work?

Nelfinavir interferes with the life cycle of HIV to stop it from producing more virus. Specifically, nelfinavir ties up the protease enzyme, which slows the production of new virus to prevent other cells from becoming infected.

How do I take it?

  • Nelfinavir is available as 250 mg and 625 mg tablets.
  • The dose varies but can be 750 mg (three 250 mg tablets) three times daily or 1250 mg (two 625 mg tablets) twice daily.
  • Nelfinavir must be taken within 2 hours of a meal to increase absorption of the medication into the bloodstream.

It is extremely important that you take nelfinavir and your other antiretroviral medications exactly as directed. You should set up a system that will help you remember to take your medicines so that you do not miss any doses. If you miss a dose, take it as soon as possible; however, if you skip a dose, do not take two doses at once. Do not stop taking the medication for any reason at any time unless you are directed to do so by your study clinician. If you are unable to continue taking your medication due to side effects, you should contact your study clinician immediately.

Special Considerations

  • Nelfinavir should be stored at controlled room temperature in a dry place, out of reach of children.
  • Please bring your medication bottles (empty and partially used) to each study visit.


Some drugs taken together may have interactions that cause illness or impair the effectiveness of the drugs. Nelfinavir has a number of serious drug interactions. You need to be familiar with the names of medications that you are taking and compare them to the medications listed below. Make sure that everyone who is prescribing or dispensing medications to you knows that you are taking nelfinavir.

Nelfinavir should not be taken with any of the following medications:

  • astemizole (Hismanal®)
  • cisapride (Propulsid®)
  • rifampin (Rifadin®)
  • terfenadine (Seldane®
  • triazolam (Halcion®)

Inform your study clinician if you are taking any of the following medications:

  • carbamazepine (Tegretol®)
  • diltiazem (Cardizem®)
  • felodipine (Plendil®)ergotamine
  • nifedipine (Procardia®)
  • rifabutin (Mycobutin®
  • phenobarbital
  • phenytoin (Dilantin®)
  • verapamil (Calan®, Isoptin®)

Many other drugs may interact with nelfinavir so you must tell your provider about all medications you are currently taking. This includes any medications that you may take on an ‘as needed’ basis, such as sleeping pills or pain medications and herbal or natural medicines.

If you are taking oral contraceptives with nelfinavir, an alternate form of birth control should be used.

Side Effects

Not everyone experiences side effects. When they do occur, they may be mild, moderate or severe. Some side effects cannot be felt by the patient but can be found through laboratory tests, so it is important to see your study clinician regularly for checkups so that side effects can be detected early and treated.

The most common side effect of nelfinavir is diarrhea. Diarrhea can usually be controlled with an over-the-counter drug called loperamide (Immodium®). Other side effects that may occur include abdominal pain, nausea, gas pain, or rash.

Rarely, nelfinavir may cause a decrease in white blood cells, red blood cells, or a change in liver function. These side effects can be detected and monitored with laboratory tests.

Increases in blood sugar or the development of diabetes has been reported in a small number of patients taking protease inhibitors. Symptoms of this include increased thirst or hunger, weight loss, increased need to urinate, fatigue, or dry, itchy skin. Please contact your study clinician if any of these side effects occur.

Also, a condition called lipodystrophy (abnormal use of fats in the body) has been reported in patients taking protease inhibitors. Symptoms vary among individuals, but they may include accumulation of fat tissue in the stomach area or the upper back, and a loss of mass in other areas of the body. Some people have experienced increases in cholesterol and triglycerides that have required the use of lipid lowering medications.

The benefits of taking protease inhibitors far outweigh the risk of developing lipodystrophy or diabetes. Therefore, at this time, we strongly encourage you to take your medications exactly as prescribed. Notify your study clinician if any of these side effects are bothersome and may prevent you from taking your medication.

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