Oseltamivir

Neuraminidase Inhibitor·Infectious Diseases - Antivirals

Treatment and post-exposure prophylaxis of Influenza A and B

PBSANTIVIRALTamiflu30 mgS4+1

Max Dose

150 mg/day

Half-life

6-10 h

48-Hour Window

CRITICAL

Psych Risk

PAEDS

Rapid Summary

Overview

Oral neuraminidase inhibitor. The primary antiviral for Influenza A and B. Reduces symptom duration by ~1 day and significantly lowers ICU admission/mortality in high-risk patients.

Maximum Dose

Max 150 mg/day (e.g., 75 mg BD).

Clinical Focus

Efficacy drops to near-zero if started more than 48 hours after symptom onset in healthy adults (though still used late in severe ICU cases).

Bottom Line

Oseltamivir is the standard antiviral for influenza treatment and prophylaxis, but must be started within 48 hours of symptom onset and provides only modest reduction in illness duration.

Formulation & Access

Brand Names

Tamiflu

Oral Routes

Capsules (30 mg, 45 mg, 75 mg). Oral powder for suspension (6 mg/mL).

Prescribing & PBS

Unrestricted General Benefit (S4).

Indications & Use

Primary

PBSTGA

Treatment and post-exposure prophylaxis of Influenza A and B.

Clinical Place

Crucial during winter flu seasons to protect frail elderly, pregnant women, and immunocompromised patients from fatal viral pneumonitis.

Quick reference

Class & Role

Neuraminidase Inhibitor — Oral neuraminidase inhibitor.

Route / Formulation

Capsules (30 mg, 45 mg, 75 mg). Oral powder for suspension (6 mg/mL). (Tamiflu)

Usual Dose & Max

PO 75 mg BD for 5 days. (Must start ASAP, ideally within 48h of fever). Max 150 mg/day (e.g., 75 mg BD).

Key Indication Doses

Influenza Treatment: PO 75 mg BD for 5 days. (Must start ASAP, ideally within 48h of fever). Influenza Prophylaxis: PO 75 mg OD for 10 days. (Used during ward outbreaks or for highly vulnerable contacts). Renal Impairment: Reduce treatment dose to 30 mg BD if eGFR 10-30. Max 30 mg OD if eGFR < 10.

Best Uses

Oseltamivir is the standard antiviral for influenza treatment and prophylaxis, but must be started within 48 hours of symptom onset and provides only modest reduction in illness duration.

Avoid / Cautions

Severe hypersensitivity. Pregnancy Category B1. Influenza in pregnancy is extremely lethal; Oseltamivir is strongly recommended for pregnant women at any stage if they contract the flu.

Key Risks

Gastrointestinal: Nausea, vomiting (Take with food to minimize this, it does not affect absorption). Neurological: Rare but severe neuropsychiatric events (delirium, hallucinations, suicidal behavior), predominantly observed in children and adolescents (Japan data).

Key Interactions

Live Attenuated Influenza Vaccine (LAIV). Oseltamivir will kill the live vaccine. Do not give LAIV within 2 weeks of taking Oseltamivir. (Note: Standard Australian flu shots are INACTIVATED and do not interact).

Monitoring

Warn parents to monitor children closely for sudden bizarre behavior, delirium, or self-harm ideation after starting the drug. Check eGFR in the elderly.

Clinical Pearl

While the '48-hour rule' applies to healthy people at home, if a patient is admitted to ICU with severe influenza pneumonia on Day 5, we STILL give them Oseltamivir, as evidence shows it continues to reduce mortality in severe systemic disease.

Access

Tamiflu30 mg

Brand: Tamiflu
Formulation: Capsules (30 mg, 45 mg, 75 mg)

Oseltamivir

Neuraminidase Inhibitor·Infectious Diseases - Antivirals

Treatment and post-exposure prophylaxis of Influenza A and B

PBSANTIVIRALTamiflu30 mgS4+1

Max Dose

150 mg/day

Half-life

6-10 h

48-Hour Window

CRITICAL

Psych Risk

PAEDS

Rapid Summary

Overview

Oral neuraminidase inhibitor. The primary antiviral for Influenza A and B. Reduces symptom duration by ~1 day and significantly lowers ICU admission/mortality in high-risk patients.

Maximum Dose

Max 150 mg/day (e.g., 75 mg BD).

Clinical Focus

Efficacy drops to near-zero if started more than 48 hours after symptom onset in healthy adults (though still used late in severe ICU cases).

Bottom Line

Oseltamivir is the standard antiviral for influenza treatment and prophylaxis, but must be started within 48 hours of symptom onset and provides only modest reduction in illness duration.

Formulation & Access

Brand Names

Tamiflu

Oral Routes

Capsules (30 mg, 45 mg, 75 mg). Oral powder for suspension (6 mg/mL).

Prescribing & PBS

Unrestricted General Benefit (S4).

Indications & Use

Primary

PBSTGA

Treatment and post-exposure prophylaxis of Influenza A and B.

Clinical Place

Crucial during winter flu seasons to protect frail elderly, pregnant women, and immunocompromised patients from fatal viral pneumonitis.

Quick reference

Class & Role

Neuraminidase Inhibitor — Oral neuraminidase inhibitor.

Route / Formulation

Capsules (30 mg, 45 mg, 75 mg). Oral powder for suspension (6 mg/mL). (Tamiflu)

Usual Dose & Max

PO 75 mg BD for 5 days. (Must start ASAP, ideally within 48h of fever). Max 150 mg/day (e.g., 75 mg BD).

Key Indication Doses

Best Uses

Oseltamivir is the standard antiviral for influenza treatment and prophylaxis, but must be started within 48 hours of symptom onset and provides only modest reduction in illness duration.

Avoid / Cautions

Severe hypersensitivity. Pregnancy Category B1. Influenza in pregnancy is extremely lethal; Oseltamivir is strongly recommended for pregnant women at any stage if they contract the flu.

Key Risks

Key Interactions

Monitoring

Warn parents to monitor children closely for sudden bizarre behavior, delirium, or self-harm ideation after starting the drug. Check eGFR in the elderly.

Clinical Pearl

Access

Tamiflu30 mg

Brand: Tamiflu
Formulation: Capsules (30 mg, 45 mg, 75 mg)