Brand name: Fuzeon
Generic name: enfuvirtide, T-20, or ENF
Class: Fusion inhibitor (a type of entry inhibitor)
AWP: $3,999.09/month for 90 mg kit
Standard Dose: One subcutaneous (under the skin, like insulin) injection of 90 mg (1 mL) twice daily (every 12 hours) into the upper arm, thigh, or abdomen. Each injection should be given in a different location from the previous one and at a site where there is no current injection site reaction from a previous dose. It is also approved for children 6 years or older. The dose for children is based on weight. Can be taken with or without food, with no dietary restrictions. Take missed dose as soon as possible, unless it is closer to the time of your next dose. Do not double up on your next dose.
Potential side effects and toxicity: The most common are injection site reactions (ISRs), which occur in virtually all patients. The severity of reaction is variable, and for most is mild to moderate. Symptoms could include itching, swelling, redness, pain or tenderness, and hardened skin or bumps. Bumps, termed "nodules," seem to occur more frequently and severely in areas of high muscle mass (most notably the center of the stomach -- the abs -- and the thighs). They will hurt with movement. Other side effects may include diarrhea, nausea, and fatigue, but these are more likely due to the other HIV medications taken along with Fuzeon. Hypersensitivity (allergic-like) reactions are possible. Results of a post-marketing observational study were added to Fuzeon's drug label last year, showing a higher incidence of pneumonia in people taking Fuzeon. Risk factors for pneumonia included a low CD4+ T-cell count or high viral load when starting therapy, intravenous drug use, smoking, and a previous history of lung disease. It is unclear if this was related to the use of Fuzeon, so report cough, fever, or trouble breathing to your health care provider immediately. See chart for potential drug class side effects.
Potential drug interactions: To date, none that are clinically significant have been found.
More information: With other powerful, newer drugs on the market, the twice-daily injectable Fuzeon is truly a medicine of last resort. Fuzeon is intended for treatment-experienced patients. Store kit at room temperature. Preparing and injecting Fuzeon can be complicated, so ask your health care provider to teach you how to do it. First, the drug needs to be dissolved with sterile water (provided in the kit), which may take up to 45 minutes. Never shake the vial with the Fuzeon, it will foam. Instead, roll it gently in your hands. To save time, you can prepare the two daily doses at the same time. You should store your second dose in the refrigerator, but it must be used within 24 hours of mixing it (allow it to warm to room temperature before using). Before injecting, it is important to make sure that the Fuzeon powder is completely dissolved. To minimize injection site reactions, inject where you can pinch an inch (upper arm, stomach, or thigh). If not, then be sure to use half the length of the needle. Inject slowly and apply a gentle massage after injection. Try using vibrating devices after injections. Using insulin syringes to inject instead of the ones in the kit may help decrease the injection site reactions. Taking a shower before injecting helps warm and soften the skin and may also help reduce injection site reactions. Some patients use Arnica cream to decrease the inflammation. Follow proper hygiene instructions to avoid infection. ISR may worsen when injection is repeated in the same spot or given deeper than intended, for example, into the muscle. Always rotate injection sites frequently. Never inject into moles, scars, bruises, nodules, or the navel. Fuzeon can be taken at the same time as other anti-HIV drugs. Fuzeon is the only anti-HIV compound on the market called a fusion inhibitor. Fusion inhibitors block fusion of HIV with a cell before the virus enters the cell and begins its replication process. Fusion inhibitors are a type of entry inhibitor (see Selzentry). See package insert for more complete information on potential side effects and interactions.
Fuzeon inhibits fusion of the virus with the CD4 cell membrane, the final stage in the entry process. It was our first true "salvage drug," a drug to be used in people with highly resistant virus. In fact, the original TORO trials not only led to the approval of Fuzeon, but ushered in the era of salvage therapy and set the standard for clinical trial design that would later lead to the approval of drugs like Prezista, Isentress, Selzentry, and Intelence. However, Fuzeon, never a big seller, is now rarely used. For most people, even those with the most highly resistant virus, there are easier, less expensive options that don't require twice-daily subcutaneous injections that leave long-lasting painful bumps on the skin (injection site reactions, or ISRs). But I wouldn't dismiss Fuzeon altogether. We may be in a "honeymoon period" with respect to salvage therapy, when almost everyone can keep their viral load undetectable with a combination of oral drugs. But the pipeline of drugs for treatment-experienced patients isn't exactly gushing right now, and if we begin to see a lot of resistance to the newer drugs, especially Isentress, we may be forced to pull Fuzeon off the shelves again.
-- Joel Gallant, M.D., M.P.H.
I'm not sure where to go with this one. For the very rare person on salvage therapy, this might be needed. But with the introduction of so many new second-generation drugs a few years back, this has become somewhat of a moot point. The site injection sores made it unlikely for most folks to use it. I remember they would send nurses out to teach people how to inject themselves, and the costs to the system of care were high. I guess this could keep people going until newer drugs come out, but I doubt we'll ever see Fuzeon come to the forefront.
-- Joey Wynn
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