What is the recommended treatment for influenza (flu) in primary care?

Treatment for Influenza in Primary Care

For patients presenting within 48 hours of symptom onset with confirmed or suspected influenza, initiate oseltamivir 75 mg twice daily for 5 days, prioritizing treatment for high-risk patients and those with severe illness. 1, 2

Antiviral Treatment Recommendations

Who Should Receive Antiviral Treatment

Mandatory treatment groups (do not delay while awaiting test results):

• All hospitalized patients with suspected influenza 1
• Patients with severe, complicated, or progressive illness regardless of time from symptom onset 1
• High-risk patients including:
  • Children <2 years (especially <6 months) 1
  • Adults ≥65 years 1
  • Patients with chronic pulmonary disease (including asthma), cardiovascular disease (except hypertension alone), renal, hepatic, hematological, metabolic (including diabetes), or neurologic conditions 1
  • Immunosuppressed patients 1
  • Pregnant women 1

Consider treatment for:

• Previously healthy outpatients presenting within 48 hours of symptom onset, based on clinical judgment 1
• Patients with COPD or other severe pre-existing illnesses, even without pneumonia 1

Antiviral Drug of Choice

Oseltamivir (Tamiflu) is the preferred antiviral agent 1:

• Adult dosing: 75 mg orally twice daily for 5 days 1, 2
• Pediatric dosing (≥1 year): Weight-based dosing using oral suspension 1, 2
  • ≤15 kg: 30 mg twice daily
  • 15.1-23 kg: 45 mg twice daily
  • 23.1-40 kg: 60 mg twice daily

  • 40 kg: 75 mg twice daily

• Renal adjustment: Reduce dose by 50% if creatinine clearance <30 mL/min 1
• Tolerability: Take with food to reduce nausea (occurs in ~10% of patients) 1

Zanamivir is an alternative neuraminidase inhibitor 3:

• Not recommended for patients with underlying airways disease (asthma, COPD) due to risk of serious bronchospasm 3
• Dosing: 10 mg (two 5-mg inhalations) twice daily for 5 days 3
• Only for patients ≥7 years for treatment, ≥5 years for prophylaxis 3

Timing of Treatment

Treatment is most effective when started within 24 hours of symptom onset 4:

• Ideally initiate within 48 hours of symptom onset 1, 2
• Benefits include: reduction of illness duration by approximately 24 hours, possible reduction in hospitalization, and decreased subsequent antibiotic use 1
• For high-risk patients with severe illness, treatment can be initiated >48 hours from onset 1

Antibiotic Management

When NOT to Use Antibiotics

Antibiotics are not routinely required for previously healthy patients with uncomplicated influenza 1:

• Influenza is a viral illness; antibiotics have no effect on viral infections 5
• Acute bronchitis symptoms (cough, retrosternal discomfort, wheeze, sputum) are part of the influenzal illness and do not require antibiotics 1

When to Consider Antibiotics

Consider antibiotic use in the following situations 1:

• Previously well patients with significant worsening of symptoms, particularly recrudescent fever or increasing breathlessness (suggesting secondary bacterial infection) 1, 5
• Patients with COPD and/or other severe pre-existing illnesses 1
• All patients with influenza-related pneumonia 1

Antibiotic choices when indicated 1:

• First-line: Doxycycline (tetracycline) or co-amoxiclav (amoxicillin-clavulanate) 1
• Alternative: Macrolides (clarithromycin preferred over erythromycin due to better H. influenzae activity) 1
• Delayed prescription strategy: For selected patients, provide antibiotic prescription with instructions to use only if illness not settling after 2 days or if symptoms worsen 1

Clinical Approach Algorithm

1. Assess presentation timing: Is patient within 48 hours of symptom onset? 1
2. Identify risk status: Does patient have high-risk conditions or severe illness? 1
3. Initiate oseltamivir for high-risk patients or those with severe illness presenting within 48 hours 1, 2
4. Assess for complications: Look for signs of pneumonia (new focal chest signs) or bacterial superinfection (recrudescent fever, increasing dyspnea) 1
5. Add antibiotics only if pneumonia present or secondary bacterial infection suspected 1

Important Caveats

• Do not delay treatment while awaiting diagnostic test results in high-risk patients 1
• Oseltamivir does not reduce transmission to others; patients should still practice infection control measures 3
• Evidence does not suggest mortality reduction with antivirals, though this is not ruled out 1
• Focus GP efforts on assessment and management of high-risk patients and those developing complications 1
• Annual influenza vaccination remains the primary preventive measure; antivirals are not a substitute 5, 3