SYNAGIS
Clinical safety rating: caution
Comprehensive clinical and safety monograph for SYNAGIS (SYNAGIS).
Palivizumab is a humanized monoclonal antibody that binds to the A antigenic site of the fusion (F) protein of respiratory syncytial virus (RSV), inhibiting viral entry into host cells by preventing fusion of the viral envelope with the host cell membrane.
| Metabolism | Palivizumab is a monoclonal antibody; it is degraded into small peptides and amino acids via catabolic pathways, similar to endogenous IgG. No specific metabolic enzymes are involved. |
| Excretion | Renal: minimal intact IgG recovered in urine; likely catabolized to peptides/amino acids. Fecal/biliary: not significantly eliminated. Main route: proteolytic catabolism. |
| Half-life | 18-27 days (terminal half-life in pediatric patients, mean ~21 days). Allows monthly dosing during RSV season. |
| Protein binding | ~98-99% bound, primarily to IgG receptors (FcRn) and endogenous IgG; binding to other serum proteins minimal. |
| Volume of Distribution | ~1.0-1.5 L/kg in infants; reflects distribution primarily within vascular space and extracellular fluid. |
| Bioavailability | IM: ~80-100% (nearly complete absorption after intramuscular injection). |
| Onset of Action | IM: Serum neutralizing titers peak by 48-72 hours but protective levels achieved within 1-2 days. |
| Duration of Action | ~1 month; requires monthly doses throughout RSV season due to half-life. |
15 mg/kg intramuscular once monthly during RSV season. Maximum dose: 300 mg (2 mL) per injection.
| Dosage form | VIAL |
| Renal impairment | No dose adjustment required for renal impairment. |
| Liver impairment | No dose adjustment required for hepatic impairment. |
| Pediatric use | Infants and children up to 24 months: 15 mg/kg intramuscular once monthly during RSV season. Maximum dose: 300 mg per injection. |
| Geriatric use | Not indicated for use in adults; no geriatric dosing data available. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for SYNAGIS (SYNAGIS).
| Breastfeeding | Not known whether palivizumab is excreted in human milk. IgG antibodies are transferred into milk, but systemic absorption by the infant is minimal. M/P ratio not established. Consider developmental benefits of breastfeeding versus theoretical risk of exposure. Caution advised. |
| Teratogenic Risk | Pregnancy Category B. Animal studies have not demonstrated fetal risk, but no adequate human studies in pregnant women. Palivizumab is a humanized monoclonal antibody (IgG1) that crosses the placenta, with increasing transfer in the second and third trimesters. No teratogenic effects have been reported. Use only if clearly needed. |
■ FDA Black Box Warning
None
| Serious Effects |
["History of severe hypersensitivity reaction to palivizumab or any component of the product"]
| Precautions | ["Anaphylaxis and hypersensitivity reactions (rare but severe)","Coagulation disorders (thrombocytopenia) with bleeding complications in patients with CHD","Risk of infection transmission if administered with contaminated equipment","Not indicated for treatment of RSV disease","May interfere with RSV diagnostic tests"] |
Loading safety data…
| Fetal Monitoring | No specific maternal or fetal monitoring required beyond standard obstetrical care. Monitor for signs of hypersensitivity reactions during and after administration. For preterm infants, monitor for respiratory syncytial virus (RSV) infection and adverse effects. |
| Fertility Effects | No studies on fertility effects in humans. Animal reproduction studies have not indicated impaired fertility. No known impact on male or female fertility. |