Antiviral (Neuraminidase Inhibitor) Pregnancy: C — use if benefits outweigh risks

Oseltamivir

Brand names: Tamiflu

Adult dose

Dose: Treatment: 75mg twice daily × 5 days. Prophylaxis: 75mg once daily × 10 days

Route: Oral

Frequency: Twice daily (treatment) or once daily (prophylaxis)

Reduce dose in renal impairment: CrCl 10–30 → 75mg OD for treatment; 30mg OD for prophylaxis. Start within 48h of symptom onset.

Paediatric dose

Route: Oral

Frequency: Twice daily × 5 days

Weight-based dosing: ≤15kg: 30mg BD; 15–23kg: 45mg BD; 23–40kg: 60mg BD; >40kg: 75mg BD. Neonates/infants: 3mg/kg BD (off-label). Suspension available (12mg/mL).

Clinical pearls

Start within 48 hours for maximum benefit — evidence weakens with later use
Recommended for at-risk groups: pregnant, immunocompromised, chronic cardiorespiratory disease
NICE: reserve for higher-risk patients during annual seasonal influenza
Neuropsychiatric warning (especially Japanese paediatric data): monitor for unusual behaviour, self-harm
H5N1 and H7N9 avian influenza: double dose 150mg BD for 10 days (off-label)

Contraindications

Hypersensitivity

Side effects

Nausea and vomiting (take with food to reduce)
Headache
Neuropsychiatric effects (mainly adolescents — monitor for unusual behaviour)
Rash

Interactions

Live attenuated influenza vaccine (LAIV) — avoid oseltamivir within 48h before or 2 weeks after LAIV
Probenecid — increases oseltamivir levels (reduces renal secretion of carboxylate metabolite)
No significant interactions with common paediatric drugs

Monitoring

Symptoms resolution
Neuropsychiatric behaviour (adolescents)
Renal function (dose adjust)

Reference: BNFc; NICE TA168; PHE Influenza Guidelines; BNF for Children. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways