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 |
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 | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for FUZEON (FUZEON).
| Breastfeeding | Unknown if distributed in human milk. M/P ratio not established. Due to potential for HIV transmission and adverse effects, breastfeeding is contraindicated in HIV+ mothers. |
| 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 |
■ FDA Black Box Warning
None.
| Serious Effects |
["Hypersensitivity to enfuvirtide or any component of the formulation"]
| 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"] |
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| 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. |