What is the full prescription for Tamiflu (Oseltamivir)?

Tamiflu (Oseltamivir) Full Prescription

For treatment of influenza in adults and adolescents ≥13 years, prescribe oseltamivir 75 mg orally twice daily for 5 days, initiated within 48 hours of symptom onset. 1, 2

Treatment Dosing

Adults and Adolescents (≥13 years)

• 75 mg orally twice daily for 5 days 1, 3, 2
• Can be taken with or without food, though taking with meals reduces gastrointestinal side effects (nausea, vomiting) 1, 3, 2
• Must be initiated within 48 hours of symptom onset for maximum benefit, though treatment should not be withheld in high-risk or hospitalized patients presenting beyond 48 hours 3, 2

Pediatric Patients (1-12 years) - Weight-Based Dosing

All doses given twice daily for 5 days: 1, 3

• ≤15 kg (≤33 lb): 30 mg twice daily
• >15-23 kg (>33-51 lb): 45 mg twice daily
• >23-40 kg (>51-88 lb): 60 mg twice daily
• >40 kg (>88 lb): 75 mg twice daily

Infants (2 weeks to <12 months)

• 9-11 months: 3.5 mg/kg per dose twice daily for 5 days 1, 3
• Term infants 0-8 months: 3 mg/kg per dose twice daily for 5 days 1, 3

Preterm Infants (Postmenstrual Age-Based)

All doses given twice daily for 5 days: 1, 3

• <38 weeks postmenstrual age: 1.0 mg/kg per dose
• 38-40 weeks postmenstrual age: 1.5 mg/kg per dose
• >40 weeks postmenstrual age: 3.0 mg/kg per dose

Prophylaxis Dosing

Post-Exposure Prophylaxis (Adults and Adolescents ≥13 years)

• 75 mg orally once daily for 10 days 1, 3, 4, 2
• Must be initiated within 48 hours following close contact with an infected individual 3, 4, 2

Seasonal Prophylaxis (Community Outbreak)

• 75 mg orally once daily for up to 6 weeks during period of community influenza activity 2

Pediatric Prophylaxis (1-12 years)

Same weight-based doses as treatment, but once daily for 10 days (or up to 6 weeks during community outbreak): 1, 3

• ≤15 kg: 30 mg once daily
• >15-23 kg: 45 mg once daily
• >23-40 kg: 60 mg once daily
• >40 kg: 75 mg once daily

Infant Prophylaxis (3-11 months)

• 3 mg/kg once daily for 10 days 3, 5
• Not recommended for infants <3 months unless situation is judged critical due to limited safety data 5

Renal Impairment Adjustments

Treatment Dosing

• CrCl >30-60 mL/min: 30 mg twice daily for 5 days 2
• CrCl 10-30 mL/min: 30 mg once daily for 5 days 1, 3, 5, 2
• ESRD on hemodialysis: 30 mg immediately, then 30 mg after every hemodialysis cycle (not to exceed 5 days) 2
• ESRD on CAPD: Single 30 mg dose immediately 2

Prophylaxis Dosing

• CrCl >30-60 mL/min: 30 mg once daily 2
• CrCl 10-30 mL/min: 30 mg once every other day OR 75 mg every other day for 10 days (5 total doses) 1, 3, 5, 2
• ESRD on hemodialysis: 30 mg immediately, then 30 mg after alternate hemodialysis cycles 2
• ESRD on CAPD: 30 mg immediately, then 30 mg once weekly 2
• Not recommended for ESRD patients not on dialysis 2

Formulations and Administration

Available Forms

• Capsules: 30 mg, 45 mg, 75 mg 1, 3, 2
• Oral suspension: 6 mg/mL when reconstituted from powder 1, 3, 2

Oral Suspension Dosing Volumes (6 mg/mL concentration)

• 30 mg dose = 5 mL 1, 3, 5
• 45 mg dose = 7.5 mL 1, 3, 5
• 60 mg dose = 10 mL 1, 3, 5
• 75 mg dose = 12.5 mL 1, 3, 5

Administration Tips

• Capsules can be opened and contents mixed with liquid if patient cannot swallow whole 5, 4
• If commercial suspension unavailable, pharmacist can compound suspension per package instructions (final concentration 6 mg/mL) 1, 3
• Taking with food improves tolerability and reduces nausea/vomiting 1, 3, 5, 2

Special Populations

Pregnancy and Breastfeeding

• Same dosing as non-pregnant adults (75 mg twice daily for 5 days) throughout all trimesters and postpartum period 3
• Oseltamivir is preferred over zanamivir in pregnancy 3
• Breastfeeding is not a contraindication; small amounts pass into breast milk 3, 2

Immunocompromised Patients

• Should receive treatment regardless of time since symptom onset 3
• May require extended treatment duration beyond 5 days if illness is prolonged 3

Critical Timing Considerations

• Treatment: Initiate within 48 hours of symptom onset for maximum benefit (reduces illness duration by 1-1.5 days) 3, 2, 6
• Do not delay treatment in high-risk or hospitalized patients even if presenting beyond 48 hours—substantial mortality benefit still exists 3
• Do not wait for laboratory confirmation before starting treatment in high-risk patients, as rapid tests have poor sensitivity 3
• Prophylaxis: Initiate within 48 hours of exposure to infected individual 3, 4, 2

Drug Interactions

• Live attenuated influenza vaccine (LAIV): Avoid LAIV within 48 hours before oseltamivir use, and do not use oseltamivir for 14 days after LAIV vaccination unless medically necessary 1, 5, 2
• Probenecid: May increase oseltamivir exposure 2.5-fold, but unlikely to be clinically significant 7

Common Pitfalls to Avoid

• Do not confuse treatment dosing (twice daily) with prophylaxis dosing (once daily)—this is a common prescribing error 4
• Do not delay initiation waiting for laboratory confirmation in suspected influenza 3, 4
• Do not withhold treatment in patients presenting beyond 48 hours if they are high-risk or hospitalized 3
• Do not use double-dose therapy (150 mg twice daily)—no survival benefit demonstrated 8
• Do not extend treatment beyond 5 days in routine cases; limited data support this except possibly in critically ill ICU patients 8

Contraindications

• Known serious hypersensitivity to oseltamivir or any component 2
• Hereditary fructose intolerance: One 75 mg dose of oral suspension contains 2 grams of sorbitol, exceeding daily maximum and may cause dyspepsia/diarrhea 2

Adverse Effects

• Most common (>1%): Nausea, vomiting, headache 2, 6
• Serious but rare: Stevens-Johnson syndrome, toxic epidermal necrolysis, erythema multiforme, anaphylaxis 2
• Neuropsychiatric events: Confusion, abnormal behavior (particularly in pediatric patients)—monitor closely 2
• Gastrointestinal effects are mild, transient, and reduced when taken with food 1, 6

Key Clinical Pearls

• Oseltamivir is not a substitute for annual influenza vaccination 2
• FDA-approved for infants as young as 2 weeks; can be used from birth in term and preterm infants as benefits outweigh risks 1, 3
• Preterm infants require lower weight-based dosing due to immature renal function 1, 3
• If patient misses a dose, take as soon as remembered unless within 2 hours of next scheduled dose 2