From the Guidelines
Oseltamivir (Tamiflu) can still be effective when initiated more than 48 hours after symptom onset, particularly in patients with severe, complicated, or progressive illness, or those who are hospitalized or at high risk for complications. According to the most recent and highest quality study available, treatment with oseltamivir for children with serious, complicated, or progressive disease presumptively or definitively caused by influenza, irrespective of influenza vaccination status or whether illness began greater than 48 hours before admission, continues to be recommended by the AAP, CDC, Infectious Diseases Society of America (IDSA), and Pediatric Infectious Diseases Society (PIDS) 1.
Key Points to Consider
- The standard adult dosage of oseltamivir is 75 mg twice daily for 5 days, while children receive weight-based dosing.
- Even when started late, oseltamivir may help reduce the severity and duration of symptoms, decrease viral shedding, and potentially prevent complications in vulnerable populations.
- However, the clinical benefit diminishes significantly with delayed initiation.
- Common side effects include nausea, vomiting, and headache.
- Patients should complete the full course of medication even if feeling better.
- Oseltamivir is not a substitute for annual influenza vaccination, which remains the most effective preventive measure against seasonal flu.
Clinical Judgment and Decision Making
Clinical judgment, on the basis of the patient's disease severity and progression, age, underlying medical conditions, likelihood of influenza, and time since onset of symptoms, is important to consider when making antiviral treatment decisions for high-risk outpatients. When indicated, antiviral treatment should be started as soon as possible after illness onset and should not be delayed while waiting for a definitive influenza test result, because early therapy provides the best outcomes 1.
Special Considerations
In areas with limited antiviral medication availability, local public health authorities might provide additional guidance about prioritizing treatment within groups at higher risk for complications. Current CDC guidance on treatment of influenza should be consulted; updated recommendations from CDC are available at http://www.cdc.gov/flu.
From the Research
Efficacy of Oseltamivir When Initiated More Than 48 Hours After Symptom Onset
- The efficacy of oseltamivir when initiated more than 48 hours after symptom onset is a topic of debate, with some studies suggesting that it may still be effective in reducing the duration of symptoms and virus shedding 2, 3.
- A study published in 2014 found that oseltamivir treatment started within 5 days of symptom onset reduced the median duration of symptoms by 1 day compared to placebo, although this difference was not significant in participants enrolled 48 hours or longer since illness onset 3.
- Another study published in 2014 suggested that oseltamivir may still be effective in reducing the risk of influenza-related complications, such as otitis media and lower respiratory tract complications, even when initiated more than 48 hours after symptom onset 2.
- However, a study published in 2001 found that the efficacy of oseltamivir was time-dependent, with maximal benefit observed when therapy was initiated within 48 hours of symptom onset 4.
- A study published in 2003 found that oseltamivir was effective in reducing the duration of symptoms and virus shedding in patients with influenza, including those with chronic cardiac and/or respiratory disease, although the study did not specifically examine the efficacy of oseltamivir when initiated more than 48 hours after symptom onset 5.
Key Findings
- Oseltamivir may still be effective in reducing the duration of symptoms and virus shedding when initiated more than 48 hours after symptom onset, although the evidence is not consistent 2, 3.
- The efficacy of oseltamivir is time-dependent, with maximal benefit observed when therapy is initiated within 48 hours of symptom onset 4.
- Oseltamivir may be effective in reducing the risk of influenza-related complications, such as otitis media and lower respiratory tract complications, even when initiated more than 48 hours after symptom onset 2.