[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [HIV entry inhibitors](https://durgical.com/en/pharmacology/classes/hiv-entry-inhibitors/) › Enfuvirtide

[Pharmacology](https://durgical.com/en/pharmacology/) · [HIV entry inhibitors](https://durgical.com/en/pharmacology/classes/hiv-entry-inhibitors/)

# Enfuvirtide

An injectable peptide that stops HIV fusing with the cell. It was kept for highly resistant virus and is no longer marketed in the US.

Updated 2026-11-01

- Class: [HIV entry inhibitors](https://durgical.com/en/pharmacology/classes/hiv-entry-inhibitors/)
- Target: HIV-1 envelope glycoprotein gp41
- ATC code: J05AX07

Also called: T-20

## Mechanism of action

A 36-amino-acid synthetic peptide copied from a region of gp41 itself. It sticks to a groove in gp41's first helical region and stops it folding into the six-helix bundle that fuses the viral envelope with the membrane. It does not act against HIV-2.

- gp41 unfolds after gp120 binds CD4
- Enfuvirtide sticks to its helical region
- The six-helix bundle does not form
- No membrane fusion and no virus entry

## Pharmacokinetics

**Absorption**
Subcutaneous injection; good bioavailability by this route

**Metabolism**
As a peptide it is broken down into amino acids; it does not alter other drugs' levels

## Indications

- HIV-1 infection in heavily pre-treated people with ongoing viral replication [HIV infection and AIDS →](https://durgical.com/en/conditions/hiv-infection-and-aids/)

## Adverse effects

### Common

- Injection-site reactions (pain, redness, hardening, nodules) in almost all patients
- Folliculitis

### Serious (rare, important)

- Pneumonia (seen more often)
- Hypersensitivity reactions

## Contraindications

- Previous hypersensitivity to enfuvirtide

## Key interactions

**Other drugs**
No known changes in their concentrations

## What is monitored

- Injection sites
- Respiratory symptoms with fever
- Viral load and CD4

## Administration and safety

- Subcutaneous; sites are rotated, avoiding areas with a previous reaction
- Reconstituted as the label directs and not shaken hard
- People with bleeding disorders have more risk of bleeding at the site

## Nursing care

- Teach injection technique and site rotation
- Check for nodules, redness or local infection
- Teach to seek care for cough with fever or breathing difficulty

## Pregnancy and breastfeeding

Antiretroviral treatment in pregnancy protects the mother and lowers HIV transmission to the baby; the treating team chooses the regimen.

## Memory aid

'T-20 Ties up gp41': no six-helix bundle, no fusion.

## Test yourself

Think of the answer, then tap the question to see it.

## Which step of HIV entry does enfuvirtide block?

Fusion: it stops gp41 forming the six-helix bundle that joins the viral envelope to the cell membrane.

## What is enfuvirtide's most common adverse effect?

Injection-site reactions (pain, redness, nodules), in almost all patients.

## Why is enfuvirtide injected rather than taken by mouth?

It is a peptide: it would be digested in the gut.

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## Related drugs

- [Maraviroc](https://durgical.com/en/pharmacology/maraviroc/)

## Related conditions

- [HIV infection and AIDS](https://durgical.com/en/conditions/hiv-infection-and-aids/)

[← Back to the class: HIV entry inhibitors](https://durgical.com/en/pharmacology/classes/hiv-entry-inhibitors/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [Enfuvirtide Injection: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a603023.html) (MedlinePlus (U.S. National Library of Medicine), 2025); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=J05AX07) (WHO Collaborating Centre for Drug Statistics Methodology, 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 64 (McGraw Hill, 2023).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/enfuvirtide/