ENBREL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ENBREL (ENBREL).
Tumor necrosis factor (TNF) inhibitor; etanercept is a dimeric fusion protein consisting of the extracellular ligand-binding portion of human TNF receptor p75 linked to the Fc portion of human IgG1. It binds to soluble and membrane-bound TNF, thereby blocking TNF-mediated inflammatory responses.
| Metabolism | Metabolism is via peptide hydrolysis and protein catabolism; no significant cytochrome P450 involvement. |
| Excretion | Renal: negligible; Biliary/Fecal: not significantly eliminated; primarily degraded via proteolysis into amino acids. |
| Half-life | Approximately 102 hours (range 68–170 hours) after subcutaneous administration in adults; prolonged in elderly and patients with renal impairment; supports every 2-week dosing. |
| Protein binding | ~96% bound, primarily to albumin and to a lesser extent to other plasma proteins. |
| Volume of Distribution | Approximately 0.18 L/kg (adults), indicating limited distribution primarily within the vascular and interstitial spaces; not extensively distributed into tissues. |
| Bioavailability | Subcutaneous: approximately 59% (range 50–76%) after a single 25 mg dose; absolute bioavailability not established for IV route; intramuscular route not recommended. |
| Onset of Action | Subcutaneous: clinical improvement may be observed as early as 1–2 weeks, with maximal effect by 12 weeks. |
| Duration of Action | Continuous therapeutic effect maintained with every 2-week dosing; drug levels decline below therapeutic threshold after ~4–6 weeks after last dose. |
| Action Class | Disease Modifying Anti-Rheumatoid Drugs (DMARDs)- Biologics |
| Brand Substitutes | Etacept PFS Injection, Intacept 50mg Injection, Etacept 25mg Injection, Etanerrel 25mg Injection, Enbrol 25mg Injection |
50 mg subcutaneous injection once weekly
| Dosage form | SYRINGE |
| Renal impairment | No dose adjustment required for renal impairment. Not studied in patients with severe renal impairment. |
| Liver impairment | No dose adjustment required for hepatic impairment. Not studied in patients with severe hepatic impairment. |
| Pediatric use | For juvenile idiopathic arthritis (JIA) patients aged 2 years and older: 0.8 mg/kg (max 50 mg) subcutaneously once weekly. |
| Geriatric use | No specific dose adjustment based on age alone; monitor for infections and adverse effects as elderly patients may have increased susceptibility. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ENBREL (ENBREL).
| Breastfeeding | Etanercept is excreted into breast milk in low amounts (M/P ratio approximately 0.001). Oral bioavailability is poor due to protein nature, so infant exposure is minimal. Compatible with breastfeeding, but monitor infant for infection or other adverse effects. |
| Teratogenic Risk | Etanercept is an IgG1 fusion protein that undergoes active placental transfer, increasing from the first to third trimester. Limited human data show no clear increase in major birth defects or miscarriage, but there is a potential for immunosuppression in the neonate if used in the third trimester. Animal studies show no teratogenicity. |
■ FDA Black Box Warning
Serious infections, including tuberculosis (TB), invasive fungal infections, and other opportunistic infections, have been reported. Patients should be screened for TB prior to therapy. Discontinue if serious infection develops. Malignancies, including lymphoma, have been reported in children and adolescents treated with TNF blockers.
| Serious Effects |
["Known hypersensitivity to etanercept or any component of the product","Sepsis or active infections (including chronic or localized infections)"]
| Precautions | ["Risk of serious infections (including TB, bacterial sepsis, invasive fungal infections)","Hepatitis B reactivation","Malignancies (including lymphoma, leukemia, and other malignancies)","Congestive heart failure (new onset or exacerbation)","Demyelinating disorders (e.g., multiple sclerosis, optic neuritis)","Hematologic abnormalities (including pancytopenia and aplastic anemia)","Hypersensitivity reactions","Live vaccines should not be administered concurrently"] |
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| Fetal Monitoring | Monitor for maternal infections, complete blood count, and liver function tests. In third-trimester exposure, monitor neonate for signs of immunosuppression (e.g., infections) and consider avoiding live vaccines in the first 6 months. |
| Fertility Effects | No known negative impact on fertility. TNF inhibitors may improve fertility in patients with inflammatory conditions by reducing disease activity. |