RSV Prophylaxis — Monthly Monoclonal Antibody (High-Risk Infants) Pregnancy: Not relevant — Synagis is not indicated for use in adults; data on fertility, pregnancy and lactation are not available (§4.6)

Palivizumab

Brand names: Synagis

Palivizumab is a monoclonal antibody used for passive immunoprophylaxis against severe respiratory syncytial virus (RSV) disease in high-risk infants and young children.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Not applicable — no adult dose is given in the SPC. §4.6 states 'Synagis is not indicated for use in adults'

Route: Intramuscular injection, preferably in the anterolateral aspect of the thigh

Frequency: Once a month during anticipated periods of RSV risk in the community (see paedDose)

Paediatric regimen (see paedDose for the structured value): 15 mg/kg of body weight given once a month during anticipated periods of RSV risk in the community. The volume in mL to be given at one-monthly intervals = patient weight in kg multiplied by 0.15. Where possible the first dose should be given before the RSV season starts, with subsequent doses monthly throughout the season. The efficacy of doses other than 15 mg/kg, or of dosing differently from monthly throughout the RSV season, has not been established. Most experience, including the pivotal phase III trials, is with 5 injections during one season; data on more than 5 doses are limited. The gluteal muscle should not be used routinely because of the risk of damage to the sciatic nerve; injection volumes over 1 mL should be given as a divided dose.

Paediatric dose

Dose: 15 mg/kg

Route: Intramuscular injection, preferably in the anterolateral aspect of the thigh (injection volumes over 1 mL should be given as a divided dose)

Frequency: Once a month during anticipated periods of RSV risk in the community — first dose where possible before the RSV season starts, then monthly throughout the season

Volume in mL = patient weight in kg x 0.15. The efficacy of palivizumab at doses other than 15 mg/kg, or of dosing differently from monthly throughout the RSV season, has not been established. To reduce the risk of rehospitalisation, children receiving palivizumab who are hospitalised with RSV should continue monthly doses for the duration of the RSV season. For children undergoing cardiac bypass, a 15 mg/kg injection is recommended as soon as they are stable after surgery, with subsequent doses resuming monthly through the remainder of the season for children who continue to be at high risk of RSV disease.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Paediatric weight-based calculator

Patient weight (kg)

Verify in a children's formulary

Contraindications

Hypersensitivity to the active substance or to any of the excipients, or to other humanised monoclonal antibodies (§4.3)

Side effects

Anaphylaxis and other acute hypersensitivity reactions — the most serious reactions; anaphylactic shock has in some cases been fatal (frequency not known, post-marketing)
Pyrexia (very common)
Rash (very common)
Injection site reaction (common)
Apnoea (common)
Thrombocytopenia and convulsion (uncommon, post-marketing)

Interactions

No formal drug-drug interaction studies were conducted; in the registration trial the proportions of children receiving routine childhood vaccines, influenza vaccine, bronchodilators or corticosteroids were similar between groups and no incremental increase in adverse reactions was observed (US Synagis label §7; the UK SPC §4.5 was not retrieved in this bundle)

Clinical monograph

How it works

It is a humanised monoclonal antibody directed against an epitope on the RSV fusion (F) protein, neutralising the virus and inhibiting its fusion with and entry into respiratory epithelial cells.

Prescribing in practice

Reserve for defined high-risk groups (such as certain preterm infants and those with chronic lung disease or haemodynamically significant congenital heart disease), as it is not for routine use in healthy infants.
Protection is short-lived, requiring repeated monthly injections through the RSV season to maintain antibody levels.
Administer according to the SPC and national eligibility criteria; hypersensitivity reactions can occur and require appropriate precautions.

Monitoring

Observe for hypersensitivity and injection-site reactions after each dose; no routine laboratory monitoring is required.

Counselling the patient

Explain that monthly injections through the winter season are needed to keep the baby protected against severe RSV infection.
It does not prevent all RSV infection and is reserved for babies at highest risk.
Report any signs of an allergic reaction, and keep to the schedule of repeat doses.

Evidence & guidelines

The IMpact-RSV trial established that palivizumab reduces RSV-related hospitalisation in high-risk infants, and NICE guidance defines the eligible high-risk groups for prophylaxis.

Reference: Simoes et al. NEJM 1998 (IMPACT trial); NICE TA284; MHRA SPC Synagis; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

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