From the Guidelines
Tamiflu (oseltamivir) can be used as post-exposure prophylaxis to prevent influenza after known exposure, with the recommended dosage for adults and adolescents 13 years and older being 75 mg once daily for 7 days, as per the most recent guidelines 1.
Key Considerations
- For children, the dose is weight-based: 30 mg daily for those weighing less than 15 kg, 45 mg daily for 15-23 kg, 60 mg daily for 23-40 kg, and 75 mg daily for those over 40 kg, all for 7 days.
- Treatment should ideally begin within 48 hours of exposure for maximum effectiveness.
- Common side effects include nausea, vomiting, and headache, which can be minimized by taking the medication with food.
- Tamiflu works by inhibiting the viral neuraminidase enzyme, preventing the release of new virus particles from infected cells, thus reducing viral spread within the body.
Important Notes
- It's essential to complete the full course even if feeling well, and to continue practicing good hygiene measures like handwashing to prevent further transmission.
- Tamiflu is not a substitute for annual influenza vaccination, which remains the primary method for preventing influenza infection.
- The American Academy of Pediatrics (AAP) considers oseltamivir to be the preferred postexposure chemoprophylaxis for patients with influenza A and/or B, as stated in their 2024-2025 policy statement 1.
Dosage and Administration
- Oseltamivir is administered orally or by feeding tube without regard to meals, although administration with meals may improve gastrointestinal tolerability.
- The medication is available as a generic drug or as Tamiflu in 30-mg, 45-mg, and 75-mg capsules and as a powder for oral suspension that is reconstituted to provide a final concentration of 6 mg/mL.
Special Considerations
- For infants younger than 1 year, an appropriate measuring device such as a 3-mL or 5-mL oral syringe should be used to measure the dose instead of the syringe supplied.
- In patients with renal insufficiency, the dose should be adjusted on the basis of creatinine clearance.
From the FDA Drug Label
The efficacy of oseltamivir phosphate in preventing naturally occurring influenza illness has been demonstrated in three seasonal prophylaxis (community outbreak) clinical trials and one post-exposure prophylaxis trial in household contacts In the post-exposure prophylaxis trial in household contacts (aged 13 years or older) of an index influenza case, oseltamivir phosphate 75 mg once daily or placebo taken orally was administered within 48 hours of onset of symptoms in the index case and continued for 7 days The incidence of laboratory-confirmed clinical influenza was 12% (24/200) in the placebo-treated subjects compared to 1% (2/205) in the oseltamivir phosphate -treated subjects Among household contacts 1 year to 12 years of age not already shedding virus at baseline, the incidence of laboratory-confirmed clinical influenza was lower in the group who received oseltamivir phosphate prophylaxis [3% (3/95)] compared to the group who did not receive oseltamivir phosphate prophylaxis [17% (18/106)]
Post-exposure prophylaxis with Tamiflu (oseltamivir phosphate) is effective in preventing laboratory-confirmed clinical influenza in household contacts, with a significant reduction in incidence compared to placebo. The recommended dose for post-exposure prophylaxis is 75 mg once daily for 7 days for adults and adolescents 13 years of age and older, and 30 to 60 mg taken orally once daily for 10 days for pediatric subjects 1 year to 12 years of age 2.
From the Research
Tamiflu Post Exposure Prophylaxis
- The efficacy of oseltamivir (Tamiflu) for postexposure prophylaxis (PEP) of influenza has been studied in several trials 3, 4, 5, 6.
- A study published in 2016 found that a three-day regimen of oseltamivir had a protective efficacy of 93% overall and 94% for influenza A 3.
- A systematic review and network meta-analysis published in 2024 found that oseltamivir, along with other neuraminidase inhibitors, probably achieves important reductions in symptomatic influenza in individuals at high risk of severe disease when given promptly after exposure 4.
- Another study published in 2009 reviewed the use of oseltamivir for treatment and prophylaxis of influenza infection, and found that it is effective in reducing symptom burden and preventing infection after exposure 5.
- A randomized controlled trial published in 2001 found that oseltamivir had a protective efficacy of 89% against clinical influenza in household contacts of influenza-infected individuals 6.
Efficacy in Different Populations
- A study published in 2018 investigated the clinical effectiveness of four neuraminidase inhibitors, including oseltamivir, in children with influenza A and B in Japan, and found that the duration of fever after administration was shorter in older patients and in patients with influenza A infection 7.
- The same study found that the number of biphasic fever episodes was greater in influenza B-infected patients and in younger patients 7.
Safety and Tolerability
- Oseltamivir has been found to be well tolerated, with gastrointestinal tract effects reported with similar frequency to placebo 6.
- The systematic review and network meta-analysis published in 2024 found that all six antivirals studied, including oseltamivir, do not significantly increase the incidence of drug-related adverse events or serious adverse events 4.