What is the recommended treatment and dosage of Oseltamivir (antiviral medication) for influenza A and B?

Oseltamivir Treatment for Influenza A and B

For adults and adolescents ≥13 years with influenza A or B, oseltamivir should be administered at 75 mg twice daily for 5 days, initiated within 48 hours of symptom onset for maximum effectiveness. 1, 2

Adult Dosing

• 75 mg twice daily for 5 days for treatment 1, 3, 2
• 75 mg once daily for 10 days for post-exposure prophylaxis 1, 3
• Can be extended up to 6 weeks during community outbreaks or up to 12 weeks in immunocompromised patients 3, 4

Pediatric Dosing

Weight-based dosing for children ≥12 months:

• ≤15 kg (≤33 lb): 30 mg twice daily for 5 days 1, 3, 2

• 15-23 kg (33-51 lb): 45 mg twice daily for 5 days 1, 3, 2

• 23-40 kg (51-88 lb): 60 mg twice daily for 5 days 1, 3, 2

• 40 kg (>88 lb): 75 mg twice daily for 5 days 1, 3, 2

Infant Dosing

• 9-11 months: 3.5 mg/kg per dose twice daily for 5 days 1, 2
• 0-8 months: 3 mg/kg per dose twice daily for 5 days 1, 2

Preterm Infant Dosing

Based on postmenstrual age (gestational age + chronological age):

• <38 weeks postmenstrual age: 1.0 mg/kg twice daily 1, 3, 2
• 38-40 weeks postmenstrual age: 1.5 mg/kg twice daily 3, 2

• 40 weeks postmenstrual age: 3.0 mg/kg twice daily 1, 3, 2

Renal Impairment Dosage Adjustments

• For patients with creatinine clearance 10-30 mL/min: 75 mg once daily for 5 days for treatment 1, 3
• For prophylaxis with creatinine clearance 10-30 mL/min: 30 mg once daily or 75 mg every other day for 10 days 3
• Not recommended for patients with end-stage renal disease not undergoing dialysis 4

Administration Considerations

• Can be taken with or without food, though administration with food may improve gastrointestinal tolerability 1, 3, 2
• Available as capsules (30 mg, 45 mg, 75 mg) and as powder for oral suspension (6 mg/mL when reconstituted) 3, 4
• Treatment should be initiated within 48 hours of symptom onset for maximum effectiveness; earlier initiation (within 12-24 hours) provides greater benefit 2, 5

Clinical Pearls

• Oseltamivir is effective against both influenza A and B viruses 1, 6
• Common adverse events include nausea, vomiting, and diarrhea, which are generally mild and transient 3, 7
• No clinically significant drug interactions with common medications like acetaminophen or cimetidine 8
• Avoid receipt of live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir, and don't use oseltamivir for 14 days after LAIV vaccination 3

Special Considerations

• Higher doses (150 mg twice daily) have not shown additional benefit for influenza A but may improve virologic response in influenza B 9
• For extremely preterm infants (<28 weeks), consultation with a pediatric infectious diseases physician is recommended 2

Remember that oseltamivir is not a substitute for influenza vaccination but serves as an important treatment and prophylaxis option when indicated 4.