An Overview of Viracept (Nelfinavir)

Brand Name: Viracept
Other Name(s): NFV, nelfinavir mesylate
Drug Class: Protease Inhibitors

Viracept tablet


Nelfinavir can cause serious, life-threatening side effects. These include liver problems in people with moderate or severe liver impairment and life-threatening drug interactions.

The artificial sweetener (aspartame) in nelfinavir oral powder contains phenylalanine. Phenylalanine may be harmful to people with PKU.

While taking nelfinavir, it is important to keep all of your appointments with your health care provider.

What Is Nelfinavir?

Nelfinavir is a prescription medicine approved by the U.S. Food and Drug Administration (FDA) for the treatment of HIV infection in children 2 years of age and older and adults. Nelfinavir is always used in combination with other HIV medicines.

Nelfinavir belongs to a class (group) of HIV drugs called protease inhibitors (PIs). PIs block an HIV enzyme called protease. (An enzyme is a protein that starts or increases the speed of a chemical reaction.) By blocking protease, PIs prevent HIV from multiplying and can reduce the amount of HIV in the body.

HIV medicines can't cure HIV/AIDS, but taking a combination of HIV medicines (called an HIV regimen) every day helps people with HIV live longer, healthier lives. HIV medicines also reduce the risk of HIV transmission. If you are taking HIV medicines, including nelfinavir, don't cut down on, skip, or stop taking them unless your health care provider tells you to.

What Should I Tell My Health Care Provider Before Taking Nelfinavir?

Before taking nelfinavir, tell your health care provider:

  • If you are allergic to nelfinavir or any other medicines.
  • If you have liver problems. People with moderate or severe liver problems should not use nelfinavir.
  • If you have kidney problems.
  • If you have phenylketonuria (PKU). The artificial sweetener (aspartame) in nelfinavir oral powder contains phenylalanine. Phenylalanine may be harmful to people with PKU.
  • If you have diabetes or high blood sugar.
  • If you have hemophilia.
  • If you have any other medical condition.
  • If you are pregnant or plan to become pregnant. Whether nelfinavir can harm an unborn baby is unknown. Nelfinavir should be used during pregnancy only if the potential benefits outweigh the risks. Talk to your health care provider about possible risks with taking nelfinavir when pregnant.
  • If you are breastfeeding or plan to breastfeed. Do not breastfeed if you are infected with HIV or are taking nelfinavir.
  • If you are using hormone-based birth control (such as pills, implants, or vaginal rings). Nelfinavir may make these forms of birth control less effective. Your health care provider can help you decide how to adjust your birth control while you are taking Nelfinavir. For more information about using birth control and HIV medicines at the same time, view the AIDS_info_ HIV and Birth Control infographic.
  • About other prescription and nonprescription medicines, vitamins, nutritional supplements, and herbal products you are taking or plan to take, especially St. John's wort. Nelfinavir can affect the way other medicines or products work, and other medicines or products can affect how nelfinavir works. Taking nelfinavir with certain medicines or products may cause serious, life-threatening side effects.

How Should I Take Nelfinavir?

Nelfinavir (brand name: Viracept) comes in the following forms and strengths:

  • 250-mg tablets.
  • 625-mg tablets.
  • 50-mg/g oral powder.

Take nelfinavir according to your health care provider's instructions.

Nelfinavir tablets should always be taken with a meal. If you or your child has trouble with swallowing the tablets, you can dissolve the tablets in a small amount of water. Once the tablets are dissolved, the liquid will be cloudy. Mix the cloudy liquid well and drink immediately. To make sure you or your child get the full dose of nelfinavir, add water to the glass to rinse the glass and then drink the rinse.

Nelfinavir oral powder is another option for people who have trouble with swallowing nelfinavir tablets. The oral powder may be mixed with a small amount of water, milk, formula, soy formula, soy milk, or liquid dietary supplements. Do not mix oral powder in the container that it comes in. Do not mix the powder with any acidic food or juice. Once mixed, the entire dose of nelfinavir must be taken. If the mixture is not taken immediately, it must be stored in the refrigerator, but not for longer than 6 hours.

If you are also taking the HIV medicine didanosine (brand names: Videx; Videx EC), take nelfinavir with food 1 hour after or more than 2 hours before you take didanosine.

Always take nelfinavir in combination with other HIV medicines.

If you take too much nelfinavir, contact your health care provider or local poison control center (1-800-222-1222) right away, or go to the nearest hospital emergency room.

For more information on how to take nelfinavir, see the FDA drug label from DailyMed. (DailyMed is a federal website that includes the most recent drug labels submitted to FDA.)

What Should I Do If I Forget a Dose?

If you miss a dose of nelfinavir, take the missed dose as soon as you remember it. But if it is almost time for your next dose, skip the missed dose and just take your next dose at the regular time. Do not take two doses at the same time to make up for a missed dose.

What Side Effects Can Nelfinavir Cause?

Nelfinavir may cause side effects. Many side effects from HIV medicines, such as nausea or occasional dizziness, are manageable. See the AIDS_info_ fact sheet on HIV Medicines and Side Effects for more information.

Some side effects of nelfinavir can be serious. Serious side effects of nelfinavir include liver problems in people with moderate or severe liver impairment and life-threatening drug interactions. (See the WARNING box above.)

Other possible side effects of nelfinavir include:

  • Diabetes and high blood sugar (hyperglycemia).
  • Increased bleeding in people with hemophilia.
  • Changes in body fat (including gain or loss of fat).
  • Changes in your immune system (called immune reconstitution inflammatory syndrome or IRIS). IRIS is a condition that sometimes occurs when the immune system begins to recover after treatment with an HIV medicine. As the immune system gets stronger, it may have an increased response to a previously hidden infection.
  • Diarrhea.

Tell your health care provider if you have any side effect that bothers you or that does not go away.

These are not all the possible side effects of nelfinavir. To learn more about possible side effects of nelfinavir, read the drug label or package insert or talk to your health care provider or pharmacist.

You can report side effects to FDA at 1-800-FDA-1088 (1-800-332-1088) or online at

How Should Nelfinavir Be Stored?

  • Store nelfinavir tablets and oral powder at room temperature, 59°F to 86°F (15°C to 30°C).
  • Store nelfinavir in its original container and keep the container tightly closed.
  • Do not use nelfinavir if the original seal over the container opening is broken or missing.
  • Throw away nelfinavir that is no longer needed or expired (out of date). Follow FDA guidelines on how to safely dispose of unused medicine.
  • Keep nelfinavir and all medicines out of reach of children.

Where Can I Find More Information About Nelfinavir?

More information about nelfinavir is available:

Manufacturer Information


The above Patient Version drug summary is based on the following FDA label(s): Powder, tablet (film coated).

[Note from This article was created by AIDSinfo, who last updated it on Oct. 16, 2017. We have cross-posted it with their permission.]