Makindo Medical Notes

💊 Oseltamivir (Tamiflu) is a neuraminidase inhibitor used to treat or prevent influenza A and B. It is most effective if started within 48 hours of symptom onset or given promptly after close contact with a confirmed case. Early treatment can shorten illness duration and reduce complications such as pneumonia, respiratory failure, and hospitalisation — particularly in older adults or those with comorbidities.

📘 About

• Always check the BNF entry here for the latest prescribing and renal-dose adjustment advice.
• Licensed for both treatment and post-exposure prophylaxis of influenza A and B.
• Resistance remains uncommon, but local surveillance data should be checked during outbreaks.

⚙️ Mode of Action

• Oseltamivir inhibits the viral neuraminidase enzyme on the surface of influenza virions.
• This prevents the release of new viral particles from infected epithelial cells, limiting spread within the respiratory tract.
• It is a prodrug, converted hepatically to the active metabolite oseltamivir carboxylate.

💊 Indications & Dose

• Treatment of influenza: 75 mg PO every 12 h for 5 days (start within 48 h of symptoms).
• Post-exposure prophylaxis: 75 mg PO once daily for 10 days following exposure.
• Renal impairment: Reduce dose if eGFR < 60 mL/min — check BNF for details.

⚠️ Cautions

• Use with care in renal impairment (dose adjustment required).
• Discuss risk–benefit in pregnancy and breastfeeding — may be used if benefits outweigh risks.
• Monitor for neuropsychiatric symptoms in adolescents (rare reports).

🚫 Contraindications

• Known hypersensitivity to oseltamivir or any excipient.
• Use cautiously if previous severe GI intolerance or allergic reaction.

💥 Adverse Effects

• Common: Nausea, vomiting, abdominal pain, headache, fatigue.
• Uncommon: Neuropsychiatric events (hallucinations, confusion — mainly children), arrhythmias, skin reactions, thrombocytopenia.
• Usually mild and self-limiting; take after food to improve tolerance.

🔄 Interactions

• No major interactions of clinical importance, but always review current medication list for renal-cleared antivirals.
• See BNF for comprehensive list.

📚 References

• BNF Online: Oseltamivir.
• Public Health England / UKHSA Influenza Guidelines.
• NICE NG163: COVID-19 rapid guideline — antibiotics and antivirals (includes influenza context).

🧠 Teaching Note

Oseltamivir has modest benefit in otherwise healthy adults but a clinically meaningful impact in frail or high-risk groups. Clinicians should prioritise early testing and initiation in hospitalised or immunocompromised patients during influenza season.

🕓 Revisions

• 2025-10 — Content updated and expanded by Dr O’Kane (Makindo edition).