An HIV medicine (a fusion inhibitor) given by injection
Enfuvirtide
An injectable HIV medicine (a fusion inhibitor) used as part of combination therapy when HIV has become resistant to other medicines.
What is Enfuvirtide?
Enfuvirtide is an HIV medicine called a fusion inhibitor. It is given by injection under the skin (subcutaneously), usually twice a day, and is used as part of combination therapy, always with other HIV medicines and never on its own. It is reserved for HIV that has become resistant to other treatments. Its most common side effect by far is reactions where the injection is given, such as redness, hard lumps and pain, which happen with most injections. It can also cause allergic-type reactions and a slightly higher rate of pneumonia. HIV care is provided by a specialist team.
Education and reference only. This is a plain-language guide to Enfuvirtide — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Enfuvirtide is an antiretroviral medicine used to treat HIV. It belongs to a group called fusion inhibitors, which work at a different stage from the tablets used for HIV. Unlike most HIV medicines, it is given by injection under the skin rather than by mouth, usually twice a day. Like all HIV medicines, it is only ever used as part of combination therapy, alongside other antiretrovirals and never on its own. It is a specialist medicine mainly used when HIV has become resistant to other treatments, to help build an effective combination, and is supervised by an HIV specialist team.
How it works
To infect a cell, HIV must first attach to it and then fuse its outer coat with the cell's surface so it can get inside. Enfuvirtide blocks this fusion step, so the virus cannot enter and infect new cells. Because it works at a different stage from the tablet HIV medicines, it can still be effective when the virus has become resistant to those, which is why it is used in resistant HIV. As with all HIV treatment, it is used as part of a combination so that several medicines attack the virus together, keeping the amount of virus down and protecting the immune system.
Company & origin
Originated / developed by: Specialist manufacturer.
A specialist HIV medicine used in the UK as part of combination therapy for resistant HIV, given by injection under the skin.
Practical use
How to take Enfuvirtide
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Inject it under the skin as your specialist team has trained you, usually twice a day, alongside the other HIV medicines in your combination.
- Rotate where you inject to reduce reactions at the injection site.
- Use it consistently and on time, and never on its own, as missing doses can let the virus become resistant.
- Report any signs of an allergic reaction, and any cough, fever or breathlessness that could suggest a chest infection.
- Keep all your specialist HIV appointments so treatment and side effects can be monitored.
Weighing it up
Advantages & disadvantages of Enfuvirtide
Advantages
- Works at a different stage of the virus's life cycle, so it can still help when HIV is resistant to tablet medicines.
- An important option for building an effective combination in resistant HIV.
- Adds another way of attacking the virus alongside oral HIV medicines.
Disadvantages
- Given by injection under the skin, usually twice a day, rather than as a tablet.
- Very commonly causes reactions where the injection is given, such as redness, lumps and pain.
- Can cause allergic-type reactions and was linked to a slightly higher rate of pneumonia.
Practical use
Good to know
The most important practical point with enfuvirtide is that it is an injection given under the skin, usually twice a day, so learning the injection technique and rotating where you inject is part of treatment. Almost everyone gets reactions where the injection is given, such as redness, hard lumps, swelling, itching and pain; these are very common and usually manageable but can be a nuisance over time. It can occasionally cause allergic-type reactions, which should be reported, and studies found a slightly higher rate of pneumonia in people using it. It is reserved for resistant HIV and is always used as part of a combination, taken consistently to keep the virus under control. Your specialist team will train you and review how treatment is going.
Who should not take it / use with caution
- People who have had a serious allergic reaction to enfuvirtide should not use it.
- It is used with care in people prone to chest infections, given the slightly higher pneumonia rate seen with it.
- It is not used on its own, and is used under specialist care as part of a combination, with training in injection technique.
Monitoring
- Regular blood tests including the amount of virus (viral load) and immune cells (CD4 count).
- Checking injection sites and the person's injection technique.
- Watching for allergic reactions and for signs of chest infection.
Side effects
- Reactions where the injection is given, such as redness, hard lumps, swelling, itching and pain, which are very common.
- A slightly higher rate of pneumonia (chest infection).
- Allergic-type reactions, which should be reported, sometimes coming back if the medicine is restarted.
- Tiredness, nausea or headache in some people.
Key interactions
- It has few of the medicine interactions seen with many other HIV medicines, as it works differently.
- It is used alongside other antiretrovirals chosen to build an effective combination against resistant virus.
- Tell your specialist about all your medicines so the overall combination can be reviewed.
Available as: A powder made up into a solution for injection under the skin, often given by the patient.
Answers
Enfuvirtide: frequently asked questions
What is enfuvirtide used for?
It is an HIV medicine used as part of combination therapy, mainly when HIV has become resistant to other treatments; it is always used with other HIV medicines, never alone.
How is it given?
It is given by injection under the skin, usually twice a day, and people are trained to inject it themselves.
Why do I get lumps and redness where I inject?
Reactions where the injection is given, such as redness, hard lumps and pain, are very common with enfuvirtide; rotating the injection site can help.
Why is it used for resistant HIV?
It blocks a different step of the virus's life cycle from the tablet medicines, so it can still work when the virus has become resistant to those.
Can it be used on its own?
No. Like all HIV medicines it must be part of a combination, because using one HIV medicine alone lets the virus become resistant.
The wider class
About Antiretroviral (fusion inhibitor) for HIV
Enfuvirtide belongs to the antiretroviral (fusion inhibitor) for hiv class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF
- NICE CKS
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