Drug reference

Oseltamivir

Antiviral · Antiviral (Influenza)

AntiviralAntiviral (Influenza)ATC J05AH02

CDSCO approvedSchedule HATC J05AH02

EXCRETION

—

not curated

INTERACTIONS

—

none in our sources

PREGNANCY

Limited safety data; can be used when benefit outweighs risk (e.g. pandemic)

FDA category + note

Mechanism

Oseltamivir is an ethyl ester prodrug that is hydrolyzed by hepatic carboxylesterases to oseltamivir carboxylate, a potent competitive inhibitor of influenza A and B neuraminidase. Neuraminidase cleaves terminal sialic acid residues on the host cell surface glycoproteins, and its inhibition prevents the release of newly formed virions from infected cells, trapping them on the cell surface and limiting viral spread. Efficacy requires initiation within 48 hours of symptom onset and confers activity against both influenza A (including H1N1, H5N1) and influenza B.

Indications

Treatment of influenza (most effective if started within a few hours of symptom onset; licensed for use within 48 hours of first symptoms)Post-exposure prophylaxis of influenza (when influenza is circulating in the community, given within 48 hours of exposure)Reduction of risk of complications from influenza in the elderly and in patients with chronic diseaseUse in exceptional circumstances (e.g., when vaccination does not)Treatment or post-exposure prophylaxis of influenza in children under 1 year of age (under specialist supervision)Treatment of severe influenza or in immunocompromised patients when viral shedding continues (off-label)treatment of influenza A virus infectionstreatment of influenza B virus infectionsprevention of influenza A virus infectionsprevention of influenza B virus infectionsprophylaxis and treatment of influenza A, swine flu, bird flu and influenza Bprevention of uncomplicated influenza in otherwise healthy adultstreatment of uncomplicated influenza in otherwise healthy adultsmay be beneficial during serious illnessTreatment of influenza A and B viruses (most effective if given within 48 hours of infection)Prophylaxis against influenza (throughout the season or for close contacts)Complicated influenza infections in hospitalized patientsTreatment for high-risk groups (children <2 years, adults >65 years, patients with chronic conditions, immunosuppressed individuals, pregnant women, women who have delivered infants ≤2 weeks previously, patients <19 years old receiving long-term aspirin treatment, Native Americans/Alaska Natives, morbidly obese individuals, and residents of nursing homes or chronic-care facilities)Preferred for treatment of pregnant women

Dosing

Adult: Treatment: 75 mg BD for 5 days (10 days if immunocompromised). Start within 48h of symptoms. Post-exposure prophylaxis: 75 mg OD for 10 days. Epidemic prophylaxis: 75 mg OD for up to 6 weeks.
Pediatric: 1-11 months: 3 mg/kg BD. 10-15 kg: 30 mg BD. 15-23 kg: 45 mg BD. 23-40 kg: 60 mg BD. >40 kg: 75 mg BD. Duration: 5 days treatment, 10 days prophylaxis.
Renal adjustment: CrCl 30-60: 30 mg BD (treatment), 30 mg OD (prophylaxis). CrCl 10-30: 30 mg OD (treatment), 30 mg every 48h (prophylaxis).
Max dose: 75 mg BD

Pharmacokinetics

Half-life

6–10 h (oseltamivir carboxylate)

Bioavailability

80% (oral, as oseltamivir carboxylate)

Protein binding

3% (oseltamivir carboxylate)

Metabolism

Oseltamivir phosphate is cleaved by esterases in the GI tract and liver to the active carboxylate (negligible metabolism of carboxylate)

Excretion

95% renal excretion (as oseltamivir carboxylate)

Contraindications

Poor oral intake or absorption (for oral formulation)

Side effects

Common

NauseaVomitingHeadacheDizzinessInsomniaabdominal discomfortemesisabdominal pain (due to gastric irritation, reduced by taking with food)weaknesssadnessdiarrhoeacoughskin reactionsgastrointestinal toxicityGastrointestinal symptoms (especially nausea)

Serious