FUZEON
Clinical safety rating: caution
Comprehensive clinical and safety monograph for FUZEON (FUZEON).
Fusion inhibitor; binds to gp41 of HIV-1, preventing conformational changes required for fusion with host CD4+ T-cell membrane.
| Metabolism | Not significantly metabolized by CYP450 enzymes; undergoes catabolism to amino acids. |
| Excretion | Renal: approximately 70% as unchanged drug via glomerular filtration; fecal: <5% as metabolites |
| Half-life | Terminal elimination half-life: 3.8 hours; clinically, steady-state plasma concentrations are achieved within 2-3 days with subcutaneous administration |
| Protein binding | Approximately 92% bound to human plasma proteins; primarily albumin |
| Volume of Distribution | Vd: 0.25 L/kg; indicates distribution primarily in plasma and extracellular fluid |
| Bioavailability | Subcutaneous: 84.3% relative to intravenous administration; oral: negligible (<1%) due to peptide nature and extensive first-pass metabolism |
| Onset of Action | Subcutaneous: maximal antiviral effect (HIV-1 RNA reduction) observed by week 2 of therapy |
| Duration of Action | The antiviral effect persists for the duration of dosing; due to short half-life, twice-daily subcutaneous dosing is required to maintain therapeutic concentrations |
| Molecular Weight | 4492 |
90 mg subcutaneously twice daily
| Dosage form | INJECTABLE |
| Renal impairment | No dose adjustment required for renal impairment; not significantly renally eliminated. |
| Liver impairment | No dose adjustment required for hepatic impairment; not hepatically metabolized. |
| Pediatric use | Weight-based dosing for children ≥6 years: <42.5 kg: 135 mg/m2 subcutaneously twice daily (max 90 mg); ≥42.5 kg: 90 mg subcutaneously twice daily. |
| Geriatric use | No specific dose adjustment; monitor renal function and injection site reactions due to age-related changes. |
| 1st trimester | Limited human data; in animal studies, no teratogenicity observed at doses up to 32 times the human dose. Use only if potential benefit outweighs risk. |
| 2nd trimester | No evidence of fetal harm in animal studies; limited human data. Consider use if clearly needed. |
| 3rd trimester | No evidence of fetal harm in animal studies; limited human data. May be used if benefit justifies risk. |
Clinical note
Comprehensive clinical and safety monograph for FUZEON (FUZEON).
| Placental transfer | Enfuvirtide is a large peptide (molecular weight 4492 Da) and is expected to cross the placenta in limited amounts; however, specific human data on placental transfer are not available. |
| Breastfeeding | It is unknown whether enfuvirtide is excreted in human breast milk. Because many drugs are excreted in human milk and because of the potential for adverse effects in nursing infants, a decision should be made whether to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother. |
■ FDA Black Box Warning
None.
| Serious Effects |
Hypersensitivity to enfuvirtide or any of its components
| Precautions | Hypersensitivity reactions (including rash, fever, nausea, vomiting, hypotension, respiratory distress), Increased risk of bacterial pneumonia, Injection site reactions (pain, erythema, nodules, induration), Hepatotoxicity, Immune reconstitution syndrome |
| Food/Dietary | No clinically significant food interactions. FUZEON is administered subcutaneously and meals do not affect its absorption or efficacy. |
| Clinical Pearls |
Loading safety data…
| Lactation Rating | L4 (Possibly Hazardous) |
| Teratogenic Risk | Pregnancy category B. No evidence of teratogenicity in animal studies; insufficient human data. Fetal risk cannot be excluded; use only if benefit outweighs risk across all trimesters. |
| Fetal Monitoring | Monitor maternal HIV viral load and CD4 count; assess for injection site reactions. Fetal ultrasound if exposure occurs, though no specific teratogenic pattern identified. |
| Fertility Effects | No known impact on fertility in animal studies; human data lacking. Consider standard reproductive counseling for HIV+ patients. |
| FUZEON (enfuvirtide) is the only fusion inhibitor approved for HIV-1. It must be injected subcutaneously and is used in treatment-experienced patients with multidrug resistance. Monitor injection site reactions (ISRs) closely; rotate injection sites (abdomen, thigh, upper arm). Reconstitute with sterile water for injection and use within 24 hours if refrigerated. Always combine with other antiretrovirals to prevent resistance. |
| Patient Advice | Inject FUZEON subcutaneously twice daily exactly as prescribed. · Rotate injection sites to reduce local reactions; avoid injecting into moles, scars, or irritated skin. · Do not miss doses; even a single missed dose can lead to viral rebound. · Report any signs of injection site infection (redness, swelling, warmth, pus). · Store reconstituted solution in refrigerator (2-8°C) and use within 24 hours. · Never share needles or syringes. · Use in combination with other antiretroviral drugs as part of a complete regimen. · Regular blood tests are needed to monitor viral load and CD4 count. |