Fuzeon® (Enfuvirtide, T-20)

Who should take this?

Fuzeon is used with other drugs to treat HIV in patients who have not responded well enough to other antiviral drugs. Four factors make it more likely that a patient will be successful on Fuzeon:

• Having a CD4 count higher than 100
• Having a viral load of less than 100,000
• Having used 10 or fewer HIV drugs before starting Fuzeon
• Starting Fuzeon treatment with at least two other HIV drugs that still work against HIV

As with other HIV drugs, Fuzeon works better for people with less advanced HIV. However, because Fuzeon is a new class of antiretroviral drugs, doctors may use it later in treatment after resistances to NRTIs, NNRTIs and PIs have developed. On the other hand, because Fuzeon keeps HIV from entering host cells, it can be valuable to use well before drug resistances have developed.

Fuzeon can be used in children age six or older.

There hasn’t yet been enough research done to know how Fuzeon affects pregnant women and their unborn babies. Women who are pregnant or planning to become pregnant should discuss this with their doctors before starting Fuzeon. Women with HIV should not breast feed their babies because HIV can be passed from mother to child in breast milk.

How is it taken? / Dosage

Unlike other anti-HIV drugs that are taken as pills, Fuzeon has to be injected. This is because digestion will destroy the molecules of Fuzeon.

Taking Fuzeon is similar to taking insulin when a person has diabetes. Fuzeon comes as a powder that is mixed with sterile water. The patient is given a small syringe and taught how to inject the drug under the skin. The injections are usually given on the thighs, stomach (except for the belly button) or upper arms. It should not be given any where under a belt or waistband where there might be pressure. To reduce soreness or redness, the drug should be given in a different place each time. Fuzeon should never be injected into a scar, bruise, mole or area where there is a reaction to a previous injection.

The doctor (or a nurse in his or her office) will give detailed instructions about how to mix the drug and prepare for an injection.

It is important to avoid contaminating the drug, sterile water and syringes. Needles, syringes, vials of Fuzeon or vials of sterile water should never be reused. Used needles, syringes and alcohol pads should be disposed of in the trash. However, if there is blood on an alcohol pad, it should be disposed of in a puncture-resistant container. Your doctor will tell you how to dispose of the puncture-resistant container.

Before an injection, hands should be washed with soap and water. Nothing except the drug, supplies and area where you will inject the Fuse should be touched.

When Fuzeon has been mixed with water, it may take up to 45 minutes for the powdered drug to dissolve. After Fuzeon is mixed with water, it can be stored in a refrigerator for up to 24 hours. (Write the date and time on the vial before putting it in the refrigerator.) The mixed drug should be allowed to warm to room temperature and be clear of any undissolved powder before it is injected.

Side Effects

The most common side effect people taking Fuzeon report is irritation of the skin where the drug is injected. This may include itching, swelling, pain, redness or bumps. About half the people in clinical studies described these reactions as mild, lasting only a day or two. Injecting the drug close to the skin’s surface and avoiding tender areas helps prevent skin irritation.

People taking Fuzeon with other HIV drugs may get bacterial pneumonia more often than patients who aren’t. It’s not yet clear why this is. A person on Fuzeon who has a cough, fever or trouble breathing should report this to a doctor.

Some people may be allergic to Fuzeon. Allergic reactions can be serious. If you have trouble breathing, fever with vomiting and a skin rash, blood in the urine or swelling of the feet, you should contact your doctor right away.

Other side effects that are seen more often in people using Fuzeon are:

• Constipation
• Depression
• Enlarged lymph nodes
• Loss of appetite
• Loss of sleep
• Muscle pain
• Pain and numbness in feet or legs
• Pancreas problems
• Sinus problems
• Weakness or loss of strength
• Weight loss

There may be other side effects. Call your doctor if you have any unusual problems while taking this medication.

Drug Interactions

Fuzeon does not affect other anti-HIV drugs. It can be taken at the same time as those drugs are taken. It also doesn’t affect the medicine rifampin (rifampacin, Riadin® or Rimactane®).

Resistance

As HIV copies itself and multiplies, changes sometimes happen in the new HIV copies. These are called mutations. When the virus changes, it is sometimes able to resist certain antiretroviral drugs. This is called drug resistance. Sometimes when the virus develops a resistance to one drug in a category, it will also resist other drugs in that same category. This is called cross-resistance.

Fuzeon is an important drug because it offers another drug option for people who may have already developed drug resistance or cross-resistance. It is possible for the virus to mutate and develop a resistance to fuse. This was shown in some of the early studies of Fuzeon when it alone was used to fight HIV. 

Although much more research needs to be done, there are some signs that even when HIV develops a resistance to Fuzeon, the drug still helps suppress the virus. In other words, the resistance is only partial. The drug doesn’t become totally ineffective.