Treatment of Flu-Positive Adults
For a flu-positive adult, initiate oseltamivir 75 mg orally twice daily for 5 days, ideally within 48 hours of symptom onset, as this reduces illness duration by approximately 1-1.5 days and decreases complications requiring antibiotics. 1
Antiviral Therapy
Oseltamivir (Tamiflu) is the antiviral treatment of choice for confirmed influenza in adults, administered as 75 mg orally twice daily for 5 days 2, 1
Treatment should ideally be initiated within 48 hours of symptom onset for maximum benefit, though this window may be extended in severely ill patients or those at high risk of complications 2, 1, 3
Taking oseltamivir with food may enhance tolerability and reduce nausea, which occurs in approximately 10% of patients 2, 1
Dose adjustment is required for renal impairment: reduce to 75 mg once daily if creatinine clearance is less than 30 mL/minute 2, 1
Expected Benefits
The evidence demonstrates that oseltamivir provides:
- Reduction in illness duration by 24-36 hours compared to placebo 2, 4, 5
- Decreased severity of symptoms by 38-43%, including faster resolution of fever, fatigue, and myalgia 4, 5, 6
- Significant reduction in secondary complications (11% vs 45% in high-risk patients) and subsequent antibiotic use (37% vs 69%) 5
- Faster return to normal activities and baseline health status 6
Note that current evidence does not definitively demonstrate mortality reduction, though it does not rule it out 2
Antibiotic Considerations
Antibiotics are NOT routinely indicated for uncomplicated influenza in previously healthy adults 2, 7
Consider antibiotics only in specific circumstances:
- Patients with COPD or other severe pre-existing illnesses should receive antibiotics empirically 2
- Previously well patients with worsening symptoms after initial presentation—particularly recrudescent fever or increasing breathlessness—should be strongly considered for antibiotic therapy 2
- Clinical evidence of bacterial pneumonia on examination warrants antibiotic treatment 2
First-line antibiotic choices when indicated include doxycycline, co-amoxiclav, or clarithromycin (noting that clarithromycin has better activity against H. influenzae than azithromycin) 2
Risk Stratification and Monitoring
Assess for features requiring hospital referral:
- Calculate CRB-65 score for patients with suspected influenza-related pneumonia: 1 point each for Confusion, Respiratory rate ≥30/min, Blood pressure (SBP <90 or DBP ≤60 mmHg), and age ≥65 years 2, 3
- Consider hospital referral for CRB-65 score of 1-2, with urgent admission for score ≥3 2
- Bilateral chest signs of pneumonia warrant hospital referral regardless of CRB-65 score 2
Instruct patients to seek immediate medical attention for warning signs including:
- Increasing shortness of breath or persistent high fever 3
- Chest pain, confusion, or inability to maintain oral intake 3
- Worsening symptoms after initial improvement 2
Common Pitfalls to Avoid
Do not withhold oseltamivir based solely on the 48-hour window in high-risk or severely ill patients, as they may still benefit from treatment initiated up to 5 days after symptom onset 3, 8
Do not prescribe antibiotics prophylactically without evidence of bacterial infection, as this promotes resistance without proven benefit 7
Do not use double-dose oseltamivir (150 mg twice daily), as randomized controlled trials show no significant survival benefit compared to standard dosing 8
Elderly patients may present without fever due to age-related immune changes; absence of fever should not rule out influenza or delay treatment in this population 3
Special Populations
High-risk patients (elderly, chronic cardiac/respiratory disease, immunocompromised) warrant more aggressive treatment: