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Generic name: enfuvirtide

Brand name: Fuzeon
Dosage form: subcutaneous powder for injection (90 mg)
Drug class: Miscellaneous antivirals

Medically reviewed by  A Ras MD.

What is enfuvirtide used for?

Enfuvirtide is a prescription medicine that is used to treat HIV infection.


FUZEON (enfuvirtide) is an inhibitor of the fusion of HIV-1 with CD4 cells. Enfuvirtide is a linear 36-amino acid synthetic peptide with the N-terminus acetylated and the C-terminus is a carboxamide. It is composed of naturally occurring L-amino acid residues.

Enfuvirtide is a white to off-white amorphous solid. It has negligible solubility in pure water and the solubility increases in aqueous buffers (pH 7.5) to 85-142 g/100 mL. The empirical formula of enfuvirtide is C204H301N51O64, and the molecular weight is 4492. It has the following primary amino acid sequence:

CH3CO-Tyr-Thr-Ser-Leu-Ile-His-Ser-Leu-Ile-Glu-Glu-Ser-Gln-Asn-Gln-Gln-Glu-Lys-Asn-Glu-Gln-Glu-Leu-Leu-Glu-Leu-Asp-Lys-Trp-Ala-Ser-Leu-Trp-Asn-Trp-Phe-NH2 and the following structural formula:

Chemical Structure

The drug product, FUZEON (enfuvirtide) for Injection, is a white to off-white, sterile, lyophilized powder. Each single-dose vial contains 108 mg of enfuvirtide for the delivery of 90 mg. Prior to subcutaneous administration, the contents of the vial are reconstituted with 1 mL of Sterile Water for Injection to provide the delivery of 1 mL of the solution. Each 1 mL of the reconstituted solution contains approximately 90 mg of enfuvirtide with approximate amounts of the following excipients: 22.55 mg of mannitol, 2.39 mg of sodium carbonate (anhydrous), and sodium hydroxide and hydrochloric acid for pH adjustment as needed. The reconstituted solution has an approximate pH of 9.0.

Before taking enfuvirtide, tell your doctor:

  • If you are allergic to enfuvirtide; any part of this medicine; or any other drugs, foods, or substances. Tell your doctor about the allergy and what signs you had.
  • If you are breast-feeding. Do not breast-feed while you take enfuvirtide.

This medicine may interact with other drugs or health problems.

Tell your doctor and pharmacist about all of your drugs (prescription or OTC, natural products, vitamins) and health problems. You must check to make sure that it is safe for you to take enfuvirtide with all of your drugs and health problems. Do not start, stop, or change the dose of any drug without checking with your doctor.

What are some things I need to know or do while I take enfuvirtide?

For all patients taking enfuvirtide:

  • Tell all of your health care providers that you take enfuvirtide. This includes your doctors, nurses, pharmacists, and dentists.
  • Avoid driving and doing other tasks or actions that call for you to be alert until you see how enfuvirtide affects you.
  • Do not run out of enfuvirtide.
  • Have blood work checked as you have been told by the doctor. Talk with the doctor.
  • If you smoke, talk with your doctor.
  • If you have a bleeding problem or take a blood thinner, talk with your doctor. The risk of bleeding after an injection may be higher.
  • It is common to have reactions where the injection is given. This includes pain, redness, itching, bruising, and swelling. Call your doctor if any of these effects are severe, bother you, or do not go away.
  • Nerve problems have happened when enfuvirtide was given with a certain device (Biojector 2000 needle-free device). This includes nerve pain or a burning, numbness, or tingling feeling. These effects can last up to 6 months. If you have questions, talk with the doctor.
  • This medicine does not stop the spread of diseases like HIV or hepatitis that are passed through blood or having sex. Do not have any kind of sex without using a latex or polyurethane condom. Do not share needles or other things like toothbrushes or razors.
  • This medicine is not a cure for HIV. Stay under the care of your doctor.
  • Tell your doctor if you are pregnant or plan on getting pregnant. You will need to talk about the benefits and risks of using enfuvirtide while you are pregnant.


  • If giving enfuvirtide to your child and your child’s weight changes, talk with the doctor. The dose of enfuvirtide may need to be changed.

How is enfuvirtide best taken?

Use enfuvirtide as ordered by your doctor. Read all information given to you. Follow all instructions closely.

  • Keep taking enfuvirtide as you have been told by your doctor or other health care provider, even if you feel well.
  • It is important that you do not miss or skip a dose of enfuvirtide during treatment.
  • It is given as a shot into the fatty part of the skin on the top of the thigh, belly area, or upper arm.
  • If you will be giving yourself the shot, your doctor or nurse will teach you how to give the shot.
  • Wash your hands before and after use.
  • This medicine needs to be mixed before use. Follow how to mix as you were told by the doctor.
  • Do not shake.
  • Do not use if the solution is cloudy, leaking, or has particles.
  • Do not use if solution changes color.
  • If solution is foamy or jelly-like, let sit for more time to let the drug to dissolve.
  • Move the site where you give the shot with each shot.
  • Do not give into skin that is tattooed or into irritated skin. This includes moles, scars, bruises, and burns. Do not give into areas near the elbow, knee, or groin.
  • Do not give into skin within 2 inches of the belly button.
  • Each vial is for one use only. Throw away any part not used after the dose is given.
  • Throw away needles in a needle/sharp disposal box. Do not reuse needles or other items. When the box is full, follow all local rules for getting rid of it. Talk with a doctor or pharmacist if you have any questions.

What do I do if I miss a dose?

  • Take a missed dose as soon as you think about it.
  • If it is close to the time for your next dose, skip the missed dose and go back to your normal time.
  • Do not take 2 doses at the same time or extra doses.

What are the side effects of enfuvirtide that I need to call my doctor about immediately?

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

  • Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
  • Signs of a pancreas problem (pancreatitis) like very bad stomach pain, very bad back pain, or very bad upset stomach or throwing up.
  • Fever or chills.
  • Very upset stomach or throwing up.
  • Very bad dizziness or passing out.
  • Fast breathing.
  • Eye irritation.
  • Changes in your immune system can happen when you start taking drugs to treat HIV. If you have an infection that you did not know you had, it may show up when you take enfuvirtide. Tell your doctor right away if you have any new signs after you start enfuvirtide, even after taking it for several months. This includes signs of infection like fever, sore throat, weakness, cough, or shortness of breath.
  • Very bad and sometimes deadly kidney problems have happened with enfuvirtide. Call your doctor right away if you are unable to pass urine or if you have blood in the urine or a change in the amount of urine passed.
  • A nervous system problem called Guillain-Barre syndrome has happened with enfuvirtide. Sometimes, this has been deadly. Call your doctor right away if you have weakness or a burning, numbness, or tingling feeling that is not normal.
  • Some people taking enfuvirtide may get pneumonia more often than people not taking enfuvirtide. It is not clear if this effect is caused by enfuvirtide. Call your doctor right away if you have a cough, fever, shortness of breath, or trouble breathing.

What are some other side effects of enfuvirtide?

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

  • Stomach pain or diarrhea.
  • Upset stomach.
  • Feeling tired or weak.
  • Not hungry.
  • Weight loss.
  • Sinus irritation.
  • Pain in arms or legs.
  • Flu-like signs.
  • Dry mouth.

These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.

You may report side effects to the FDA at 1-800-332-1088. You may also report side effects at https://www.fda.gov/medwatch.

If overdose is suspected:

If you think there has been an overdose, call your poison control center or get medical care right away. Be ready to tell or show what was taken, how much, and when it happened.

How do I store and/or throw out enfuvirtide?

  • Store at room temperature.
  • Store in a dry place. Do not store in a bathroom.
  • Use right away after mixing or you may store in a refrigerator for up to 24 hours.
  • Keep all drugs in a safe place. Keep all drugs out of the reach of children and pets.
  • Throw away unused or expired drugs. Do not flush down a toilet or pour down a drain unless you are told to do so. Check with your pharmacist if you have questions about the best way to throw out drugs. There may be drug take-back programs in your area.


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