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Medically reviewed by Last updated on Nov 19, 2020.


(en FYOO vir tide)

Index Terms

  • T-20

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Solution Reconstituted, Subcutaneous:

Fuzeon: 90 mg (1 ea)

Brand Names: U.S.

  • Fuzeon

Pharmacologic Category

  • Antiretroviral, Fusion Protein Inhibitor (Anti-HIV)


Binds to the first heptad-repeat (HR1) in the gp41 subunit of the viral envelope glycoprotein. Inhibits the fusion of HIV-1 virus with CD4 cells by blocking the conformational change in gp41 required for membrane fusion and entry into CD4 cells


SubQ: Absorption is comparable when injected into abdomen, arm, or thigh


Vd: 5.5 ± 1.1 L; CSF concentrations (2-18 hours after administration; n=4): nondetectable (<0.025 mcg/mL)


Expected to undergo catabolism via peptidases and proteinases in the liver and kidneys to amino acids; amino acids would then be recycled in the body pool. A deaminated metabolite (with 20% activity compared to parent drug) was formed via hydrolysis during in vitro human microsomal and hepatocyte studies.

Time to Peak

SubQ: Single dose: Median: 8 hours (range: 3 to 12 hours); Multiple dosing: Median: 4 hours (range: 4 to 8 hours)

Half-Life Elimination

3.8 ± 0.6 hours

Protein Binding

92%; primarily to albumin, but also to alpha-1 acid glycoprotein (to a lesser extent)

Use: Labeled Indications

HIV-1 infection, treatment: Treatment of HIV-1 infection in combination with other antiretroviral agents in treatment-experienced patients with evidence of HIV-1 replication despite ongoing antiretroviral therapy.


Hypersensitivity to enfuvirtide or any component of the formulation

Dosing: Adult

HIV-1 infection, treatment: SubQ: 90 mg twice daily

Dosing: Geriatric

Refer to adult dosing.

Dosing: Pediatric

HIV-1 infection, treatment: Note: Gene mutation and antiretroviral (ARV) resistance patterns should be evaluated (refer to for more information) when necessary. Although FDA approved, contemporary use is uncommon secondary to availability of more preferable options. The role in therapy is typically reserved when other options are not available; it is not recommended as initial therapy in patients who are ARV naive (HHS [pediatric] 2018).

Children weighing ≥11 kg and Adolescents:

Weight-directed dosing: SubQ: 2 mg/kg/dose twice daily; maximum dose: 90 mg/dose

Fixed dosing (weight-band): SubQ:

11 to 15.5 kg: 27 mg twice daily

15.6 to 20 kg: 36 mg twice daily

20.1 to 24.5 kg: 45 mg twice daily

24.6 to 29 kg: 54 mg twice daily

29.1 to 33.5 kg: 63 mg twice daily

33.6 to 38 kg: 72 mg twice daily

38.1 to 42.5 kg: 81 mg twice daily

≥42.6 kg: 90 mg twice daily


Reconstitute with 1 mL SWFI; tap vial for 10 seconds and roll gently between the hands to avoid foaming and to ensure contact with diluent; then allow vial to stand until complete dissolution. May require up to 45 minutes to form solution; allow more time if solution is foamy or jelled. Use immediately or refrigerate reconstituted solution and use within 24 hours; bring refrigerated solution to room temperature before administration.


SubQ: Inject subcutaneously into upper arm, abdomen, or anterior thigh. Do not inject into moles, the navel, over a blood vessel or skin abnormalities such as scar tissue, surgical scars, bruises, tattoos, or burn sites. In addition, do not inject in or near sites where large nerves are close to the skin including the elbow, knee, groin, or buttocks. Rotate injection site, give injections at a site different from the preceding injection site; do not inject into any site where an injection site reaction is evident. Bioequivalence was found to be similar in a study comparing standard administration using a needle versus a needle-free device (True 2006).


Store intact vials at 25°C (77°F); excursions are permitted between 15°C and 30°C (59°F and 86°F). Store reconstituted solution in the original vial at 2°C to 8°C (36°F to 46°F); use within 24 hours. Vials are for single use only; discard unused portion.

Drug Interactions

Orlistat: May decrease the serum concentration of Antiretroviral Agents. Monitor therapy

Protease Inhibitors: May increase the serum concentration of Enfuvirtide. Enfuvirtide may increase the serum concentration of Protease Inhibitors. Monitor therapy

Adverse Reactions

The following adverse drug reactions and incidences are derived from product labeling unless otherwise specified.


Central nervous system: Fatigue (20%), insomnia (11%)

Gastrointestinal: Diarrhea (32%), nausea (23%)

Local: Injection site reaction (98%; may include cyst at injection site, erythema at injection site, induration at injection site, injection site ecchymosis, injection site nodule, injection site pruritus, pain at injection site), injection site infection (children: 11%, adults: 2%)

1% to 10%:

Dermatologic: Folliculitis (2%)

Endocrine & metabolic: Weight loss (7%)

Gastrointestinal: Abdominal pain (4%), decreased appetite (3%), pancreatitis (3%), anorexia (2%), xerostomia (2%)

Hematologic & oncologic: Eosinophilia (2% to 9%)

Hepatic: Increased serum transaminases (4%, grade 4: 1%)

Infection: Infection (4% to 6%), herpes simplex infection (4%)

Neuromuscular & skeletal: Increased creatine phosphokinase (3% to 7%), limb pain (3%), myalgia (3%)

Ophthalmic: Conjunctivitis (2%)

Respiratory: Sinusitis (6%), cough (4%), bacterial pneumonia (3%), flu-like symptoms (2%)

<1%, postmarketing, and/or case reports: Amyloidosis (cutaneous; at the injection site), angina pectoris, anxiety, constipation, depression, dysgeusia, glomerulonephritis, Guillain-Barré syndrome, hyperglycemia; hypersensitivity exacerbation (to abacavir), hypersensitivity reaction (symptoms may include fever, hypotension, increased serum transaminases, nausea, skin rash, vomiting); increased amylase, increased gamma-glutamyl transferase, insomnia, increased serum lipase, increased serum triglycerides, liver steatosis, lymphadenopathy, neutropenia, peripheral neuropathy, pulmonary disease, renal failure, renal insufficiency, renal tubular necrosis, respiratory distress, sepsis, sixth nerve palsy, suicidal tendencies, thrombocytopenia, toxic hepatitis, weakness


Concerns related to adverse effects:

• Hypersensitivity reactions: May cause hypersensitivity reactions (symptoms may include rash, fever, nausea, vomiting, chills, rigors, hypotension, and/or elevated liver transaminases). Additionally, immune mediated reactions (eg, glomerulonephritis, Guillain-Barré syndrome, primary immune complex reaction, respiratory distress) have been reported. Discontinue therapy immediately if systemic reactions occur; do not rechallenge patient.

• Immune reconstitution syndrome: Patients may develop immune reconstitution syndrome resulting in the occurrence of an inflammatory response to an indolent or residual opportunistic infection during initial HIV treatment or activation of autoimmune disorders (eg, Graves’ disease, polymyositis, Guillain-Barré syndrome) later in therapy; further evaluation and treatment may be required.

• Injection site reactions: Local injection site reactions are common. Administration using a needle-free device has been associated with nerve pain (including neuralgia and/or paresthesia lasting up to 6 months), bruising, and hematomas when administered at sites where large nerves are close to the skin; only administer medication in recommended sites.

• Pneumonia: Monitor closely for signs/symptoms of pneumonia; associated with an increased incidence during clinical trials, particularly in patients with a low CD4 cell count, high initial viral load, IV drug use, smoking, or a history of lung disease.

Disease-related concerns:

• Bleeding disorders: Use with caution in patients with coagulation disorders (eg, hemophilia) or receiving anticoagulants; increased risk of bleeding at injection site.

• Appropriate use: Use is not recommended in antiretroviral therapy-naive patients.

Monitoring Parameters

Viral load; CD4 count; hypersensitivity and injection site reactions; pediatric weight (periodically; adjust dose accordingly); signs and symptoms of pneumonia

Reproductive Considerations

The Health and Human Services (HHS) perinatal HIV guidelines do not recommend enfuvirtide (except in special circumstances) for females living with HIV who are not yet pregnant but are trying to conceive.

For males and females living with HIV and planning a pregnancy, maximum viral suppression below the limits of detection with antiretroviral therapy (ART), modification of therapy (if needed), optimization of the woman’s health, and a discussion of the potential risks and benefits of ART therapy during pregnancy is recommended prior to conception (HHS [perinatal] 2019).

Pregnancy Considerations

Enfuvirtide has minimal to low transfer across the human placenta.

Data collected by the antiretroviral pregnancy registry are insufficient to evaluate human teratogenic risk. Maternal antiretroviral therapy (ART) may be associated with adverse pregnancy outcomes, including preterm delivery, stillbirth, low birth weight, and small for gestational age infants. Actual risks may be influenced by maternal factors, such as disease severity, gestational age at initiation of therapy, and specific ART regimen; therefore, close fetal monitoring is recommended. Because there is clear benefit to appropriate treatment, maternal ART should not be withheld due to concerns for adverse neonatal outcomes. Long-term follow-up is recommended for all infants exposed to antiretroviral medications; children without HIV but who were exposed to ART in utero and develop significant organ system abnormalities of unknown etiology (particularly of the CNS or heart) should be evaluated for potential mitochondrial dysfunction.

The Health and Human Services (HHS) perinatal HIV guidelines do not recommend enfuvirtide as initial therapy for patients living with HIV (including pregnant females); enfuvirtide is not recommended (except in special circumstances) in pregnant females who have had ART therapy in the past but are restarting, or who require a new ART regimen (due to poor tolerance or poor virologic response of current regimen). Females who become pregnant while taking enfuvirtide may continue if viral suppression is effective and the regimen is well tolerated. Pharmacokinetic data are insufficient to make dosing recommendations during pregnancy.

In general, ART is recommended for all pregnant females living with HIV to keep the viral load below the limit of detection and reduce the risk of perinatal transmission. Therapy should be individualized following a discussion of the potential risks and benefits of treatment during pregnancy. Monitoring of pregnant females is more frequent than in nonpregnant adults. ART should be continued postpartum for all females living with HIV and can be modified after delivery.

Health care providers are encouraged to enroll pregnant females exposed to antiretroviral medications as early in pregnancy as possible in the Antiretroviral Pregnancy Registry (1-800-258-4263 or Health care providers caring for pregnant females living with HIV and their infants may contact the National Perinatal HIV Hotline (888-448-8765) for clinical consultation (HHS [perinatal] 2019).

Patient Education

What is this drug used for?

• It is used to treat HIV infection.

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:

• Abdominal pain

• Diarrhea

• Loss of strength and energy

• Lack of appetite

• Flu-symptoms

• Dry mouth

• Painful extremities

• Sinus irritation

• Weight loss

• Muscle pain

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:

• Infection

• Kidney problems like unable to pass urine, blood in the urine, change in amount of urine passed, or weight gain

• Pancreatitis like severe abdominal pain, severe back pain, severe nausea, or vomiting

• Severe injection site irritation

• Chills

• Severe nausea

• Vomiting

• Weakness

• Burning or numbness feeling

• Severe dizziness

• Passing out

• Cough

• Fast breathing

• Eye irritation

• Trouble breathing

• Shortness of breath

• 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.

Note: This is not a comprehensive list of all side effects. Talk to your doctor if you have questions.

Consumer Information Use and Disclaimer: This information should not be used to decide whether or not to take this medicine or any other medicine. Only the healthcare provider has the knowledge and training to decide which medicines are right for a specific patient. This information does not endorse any medicine as safe, effective, or approved for treating any patient or health condition. This is only a limited summary of general information about the medicine's uses from the patient education leaflet and is not intended to be comprehensive. This limited summary does NOT include all information available about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this medicine. This information is not intended to provide medical advice, diagnosis or treatment and does not replace information you receive from the healthcare provider. For a more detailed summary of information about the risks and benefits of using this medicine, please speak with your healthcare provider and review the entire patient education leaflet.

Further information

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