What medications and supportive care should I prescribe for uncomplicated influenza in a healthy adult?

Treatment of Uncomplicated Influenza in Healthy Adults

For a healthy adult with uncomplicated influenza presenting within 48 hours of symptom onset, prescribe oseltamivir 75 mg orally twice daily for 5 days, along with symptomatic treatment using paracetamol (acetaminophen) for fever and body aches, rest, and adequate hydration. 1

Antiviral Therapy

Oseltamivir is the first-line antiviral agent for treating acute uncomplicated influenza in adults. 2

Dosing and Administration

• Standard adult dose: 75 mg orally twice daily for 5 days 2, 1
• Timing is critical: Treatment should ideally be initiated within 48 hours of symptom onset for maximum benefit, though the greatest benefit occurs when started within 24 hours 2, 3
• Take with food to reduce nausea, which occurs in approximately 10% of patients 2, 1
• Renal dose adjustment: Reduce to 75 mg once daily if creatinine clearance is less than 30 mL/min 1, 4

Expected Benefits

• Reduces illness duration by approximately 24-36 hours (roughly one day) compared to placebo 2, 1
• Important caveat: None of the antiviral agents have been proven to prevent serious influenza-related complications such as bacterial pneumonia or exacerbation of chronic diseases 2

Alternative Antiviral Options

• Zanamivir: 10 mg (2 inhalations) twice daily for 5 days, administered via oral inhalation 2
• Baloxavir: Single oral dose (40 mg for patients weighing 40 to <80 kg; 80 mg for patients ≥80 kg) taken within 48 hours of symptom onset 5
• Avoid zanamivir in patients with underlying asthma or COPD due to bronchospasm risk 4

Symptomatic Management

Paracetamol (acetaminophen) is the first-line antipyretic and analgesic for influenza symptoms based on its favorable safety profile. 1

Fever and Body Aches

• Use paracetamol or ibuprofen (with caution) for fever, myalgias, and headache 1
• Antipyretics should be used to alleviate distressing symptoms, not solely to reduce body temperature 1
• Continue treatment only while symptoms of fever and discomfort are present 1

Additional Supportive Care

• Rest and adequate hydration (drinking plenty of fluids, but no more than 2 liters per day) 1
• Avoid smoking 1
• Consider short-term use of topical decongestants, throat lozenges, or saline nose drops 1
• For distressing cough, consider short-term use of codeine linctus, codeine phosphate tablets, or morphine sulfate oral solution 1

Antibiotic Considerations

Antibiotics are NOT routinely indicated for previously healthy adults with uncomplicated influenza. 2, 1, 4

When to Consider Antibiotics

Antibiotics should be considered or prescribed in the following situations:

• Worsening symptoms after initial presentation: Particularly recrudescent fever or increasing breathlessness suggests possible bacterial superinfection 2, 1, 6
• Development of pneumonia: New focal chest signs or radiographic evidence of pneumonia 2, 1
• Patients with COPD or other severe pre-existing illnesses should receive antibiotics empirically 2, 4

First-Line Antibiotic Choices (When Indicated)

• Preferred: Doxycycline (200 mg loading dose, then 100 mg once daily) or co-amoxiclav (625 mg three times daily) for 7 days 2, 1
• Alternative: Macrolide such as clarithromycin (500 mg twice daily) or erythromycin (500 mg four times daily) 2, 1
• Note: Clarithromycin has better activity against Haemophilus influenzae than azithromycin 2
• These regimens provide coverage for Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae, and Moraxella catarrhalis 2, 1

Delayed Antibiotic Prescription Strategy

For selected patients, consider providing a delayed antibiotic prescription at the first consultation with clear instructions to use antibiotics only if:

• The illness is not starting to settle after 2 days, or
• There is worsening of symptoms 2

This approach minimizes rates of reconsultation while avoiding unnecessary antibiotic use. 2

Red Flags: When to Seek Immediate Medical Attention

Advise patients to return or seek urgent care if they develop:

• Shortness of breath at rest or with minimal activity 1, 6
• Painful or difficult breathing (dyspnea with chest discomfort) 1, 6
• Hemoptysis (coughing up blood-tinged sputum) 1, 6
• Persistent fever for 4-5 days without improvement 1
• Recrudescent fever (initial improvement followed by return of high fever) 2, 1
• Drowsiness, disorientation, or confusion 1

Common Pitfalls to Avoid

• Do not withhold oseltamivir in severely ill or high-risk patients even if they present beyond 48 hours of symptom onset 1, 4, 6
• Do not prescribe antibiotics routinely for uncomplicated influenza in otherwise healthy adults—this contributes to antimicrobial resistance 2, 1, 4
• Do not use amantadine or rimantadine as first-line agents; they lack activity against influenza B, frequently select resistant mutants, and cause more adverse effects 2, 7
• Do not use double-dose oseltamivir (150 mg twice daily)—no additional benefit has been demonstrated 4