Generic Name

Oseltamivir Phosphate

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Classification

FDA Approved Indications

• Treatment of acute uncomplicated influenza in patients 2 weeks and older
• Prophylaxis of influenza in patients 1 year and older

Mechanism of Action

Oseltamivir inhibits the influenza virus neuraminidase enzyme, preventing release of new viral particles from infected cells, thereby limiting viral spread.

Dosage and Administration

Adult: 75 mg twice daily for 5 days for treatment; 75 mg once daily for 10 days for prophylaxis

Pediatric: Treatment: 30-75 mg twice daily based on weight; Prophylaxis: 30-75 mg once daily based on weight, for 10 days; doses adjusted for children with renal impairment

Geriatric: Same as adults; dose adjustment recommended in renal impairment

Renal Impairment: Dose adjustment required; see prescribing information

Hepatic Impairment: No specific adjustment recommended; use with caution.

Pharmacokinetics

Absorption: Rapidly absorbed after oral administration

Distribution: Widely distributed in body tissues and fluids

Metabolism: Metabolized to an active carboxylate form by hepatic esterases

Excretion: Primarily renal excretion of unchanged drug and active metabolite

Half Life: Approximately 1-3 hours in healthy individuals

Contraindications

• Hypersensitivity to oseltamivir or any component of the formulation

Precautions

• Use with caution in patients with renal impairment; monitor for neuropsychiatric effects, especially in pediatric populations

Adverse Reactions - Common

• Nausea (More than 10% of users)
• Vomiting (More than 10% of users)
• Headache (Less than 10% of users)

Adverse Reactions - Serious

• Neuropsychiatric events (including confusion, hallucinations, abnormal behavior) (Rare)
• Anaphylaxis and serious skin reactions (Very rare)

Drug-Drug Interactions

• Live attenuated influenza vaccine (avoid concomitant use)

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Patient/Family Teaching

• Take medication with food to reduce nausea
• Complete the full course of therapy
• Report any neuropsychiatric symptoms or allergic reactions immediately
• Practice good hygiene to prevent influenza

Special Considerations

Black Box Warnings:

• Neuropsychiatric effects, including severe mental status and behavior changes, have been reported, mostly in pediatric patients

Genetic Factors: No specific genetic considerations identified

Lab Test Interference: None significant

Overdose Management

Signs/Symptoms: Nausea, vomiting, hallucinations, agitation, delirium

Treatment: Supportive care, no specific antidote; dialysis may help remove unmetabolized drug in severe cases

Storage and Handling

Storage: Store at 2°C to 25°C (36°F to 77°F).

Stability: Stable under recommended storage conditions for up to 17 months.