Skip to main content


Generic name: nelfinavir [ nel-FIN-a-veer ]
Brand name: Viracept
Dosage form: oral tablet (250 mg; 625 mg)
Drug class: Protease inhibitors

Medically reviewed by on Oct 11, 2021. Written by Cerner Multum.

What is nelfinavir?

Nelfinavir is an antiviral medicine that is used to treat HIV (human immunodeficiency virus). HIV can cause acquired immunodeficiency syndrome (AIDS). Nelfinavir is not a cure for HIV or AIDS.

Nelfinavir is for use in adults and children at least 2 years old.

Nelfinavir may also be used for purposes not listed in this medication guide.


Tell your doctor about all your other medicines. Some drugs should not be used with nelfinavir.

Before taking this medicine

You should not use nelfinavir if you are allergic to it, or if you have moderate or severe liver disease.

Some drugs should not be used with nelfinavir. Your treatment plan may change if you also use:

Tell your doctor if you have ever had:

  • liver disease;

  • kidney disease;

  • diabetes; or

  • a bleeding disorder such as hemophilia.

Nelfinavir oral powder contains phenylalanine and could be harmful if you have phenylketonuria (PKU).

To prevent HIV in a newborn baby, use all medications to control your infection during pregnancy. Your name may be listed on an antiviral pregnancy registry.

Nelfinavir can make hormonal birth control less effective, including birth control pills, injections, implants, skin patches, and vaginal rings. Use barrier birth control to prevent pregnancy: condom, diaphragm, cervical cap, or contraceptive sponge.

Women with HIV should not breastfeed. The virus can pass to your baby in your breast milk.

How should I take nelfinavir?

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

Take with food.

Swallow the nelfinavir tablet whole.

If you cannot swallow a whole tablet, dissolve it in a small amount of water. Stir and drink this mixture right away. Add a little more water to the glass, swirl gently and drink right away.

Mix the oral powder in a cup with a small amount of water, milk, baby formula, soy milk, or a liquid dietary supplement. To avoid bitter taste, do not mix the powder with acidic liquids such as orange juice, apple juice, or applesauce.

Drink all of the mixed powder right away. If a child taking nelfinavir doesn't finish the entire dose, you may store the mixture in a refrigerator for up to 6 hours.

Doses are based on weight in children. Your child's dose may change if the child gains or loses weight.

Use all HIV medications as directed. Do not change your dose or stop using a medicine without your doctor's advice. Remain under the care of a doctor.

You will need frequent medical tests.

Store at room temperature away from moisture and heat.

What happens if I miss a dose?

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

Get your prescription refilled before you run out of medicine completely.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking nelfinavir?

Using nelfinavir will not prevent your disease from spreading. Do not have unprotected sex or share razors or toothbrushes. Ask your doctor how to prevent HIV transmission during sex. Sharing drug or medicine needles is never safe.

Nelfinavir side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Nelfinavir may cause serious side effects. Call your doctor at once if you have:

  • low white blood cell counts--fever, mouth sores, skin sores, sore throat, cough;

  • high blood sugar--increased thirst, increased urination, dry mouth, fruity breath odor; or

  • if you have hemophilia--easy bruising, unusual bleeding (nose, mouth, vagina, or rectum), purple or red pinpoint spots under your skin.

Nelfinavir can affect your immune system (even weeks or months after you've used this medicine). Tell your doctor if you have:

  • signs of a new infection--fever, night sweats, swollen glands, cold sores, cough, wheezing, diarrhea, weight loss;

  • trouble speaking or swallowing, problems with balance or eye movement, weakness or prickly feeling; or

  • swelling in your neck or throat (enlarged thyroid), menstrual changes, impotence.

Common side effects of nelfinavir may include:

  • low white blood cell counts;

  • nausea, diarrhea, gas, stomach pain;

  • loss of appetite;

  • rash; or

  • changes in the shape or location of body fat (especially in your arms, legs, face, neck, breasts, and waist).

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Nelfinavir dosing information

Usual Adult Dose for HIV Infection:

1250 mg orally twice a day or 750 mg orally 3 times a day

Use: In combination with other antiretroviral agents, for the treatment of HIV-1 infection

Usual Adult Dose for Nonoccupational Exposure:

US CDC recommendations: 1250 mg orally twice a day or 750 mg orally 3 times a day
Duration of therapy: 28 days

-Recommended as part of an alternative regimen for nonoccupational postexposure prophylaxis of HIV infection
-This drug should be used with (lamivudine or emtricitabine) plus (zidovudine or stavudine or abacavir or tenofovir or didanosine).
-Prophylaxis should be started as soon as possible, within 72 hours of exposure.
-Current guidelines should be consulted for additional information.

Usual Pediatric Dose for HIV Infection:

2 to less than 13 years: 45 to 55 mg/kg orally twice a day or 25 to 35 mg/kg orally 3 times a day
Maximum dose: 2500 mg/day

-Oral powder (50 mg/g):
9 to less than 10.5 kg: 500 mg orally twice a day or 300 mg orally 3 times a day
10.5 to less than 12 kg: 550 mg orally twice a day or 350 mg orally 3 times a day
12 to less than 14 kg: 650 mg orally twice a day or 400 mg orally 3 times a day
14 to less than 16 kg: 750 mg orally twice a day or 450 mg orally 3 times a day
16 to less than 18 kg: 500 mg orally 3 times a day
18 to less than 23 kg: 600 mg orally 3 times a day
23 kg or more: 750 mg orally 3 times a day

-Tablets (250 mg):
10 to 12 kg: 500 mg orally twice a day or 250 mg orally 3 times a day
13 to 18 kg: 750 mg orally twice a day or 500 mg orally 3 times a day
19 to 20 kg: 1000 mg orally twice a day or 500 mg orally 3 times a day
21 kg or more: 1000 to 1250 mg orally twice a day or 750 mg orally 3 times a day

13 years or older:
-Tablets: 1250 mg orally twice a day or 750 mg orally 3 times a day

Comments: For twice-daily dosing, the 250 mg tablets are recommended for children weighing 16 kg or more.

Use: In combination with other antiretroviral agents, for the treatment of HIV-1 infection

What other drugs will affect nelfinavir?

If you also take didanosine, take your nelfinavir dose (with food) 1 hour after or more than 2 hours before you take didanosine.

Many drugs can affect nelfinavir, and some drugs should not be used at the same time. Tell your doctor about all other medicines you use. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed here.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.