What is the recommended treatment for influenza in adults?

Influenza Treatment in Adults

The recommended first-line treatment for influenza in adults is oseltamivir 75 mg twice daily for 5 days, started as soon as possible and ideally within 48 hours of symptom onset. 1, 2, 3

Antiviral Medication Options

First-Line Treatment

• Oseltamivir (Tamiflu)
  • Dosage: 75 mg twice daily for 5 days 1, 3
  • Can be taken with or without food (taking with food may improve gastrointestinal tolerability) 2
  • Dosage adjustment for renal impairment: 75 mg once daily for patients with creatinine clearance 10-30 mL/min 2, 3

Alternative Treatments

• Zanamivir (Relenza)

  • Dosage: 10 mg (2 inhalations) twice daily for 5 days 1
  • Not recommended for patients with underlying airways disease due to risk of bronchospasm 2

• Peramivir

  • Intravenous option for hospitalized patients 1, 2

Timing of Treatment

Timing is critical for maximizing treatment effectiveness:

• Treatment should be initiated as soon as possible after symptom onset 1
• Earlier treatment provides significantly greater benefits 4, 5:
  • Starting within 12 hours reduces illness duration by 74.6 hours (41%) 4, 5
  • Starting within 24 hours reduces illness duration by 53.9 hours 4, 5
  • Starting within 48 hours reduces illness duration by approximately 29 hours (25%) 6

Treatment Indications

Antiviral treatment should be started as soon as possible for adults with documented or suspected influenza who meet any of these criteria 1:

1. Hospitalized patients, regardless of illness duration
2. Outpatients with severe or progressive illness
3. Outpatients at high risk of complications (those with chronic medical conditions or immunocompromised)
4. Adults ≥65 years
5. Pregnant women and those within 2 weeks postpartum

Treatment can be considered for otherwise healthy adults who are not at high risk of complications 1.

Management of Complications

1. Bacterial Coinfection

   • Empiric antibacterial treatment should be initiated in patients with severe disease (extensive pneumonia, respiratory failure, hypotension, fever) 1
   • Consider antibiotics active against S. pneumoniae, S. aureus, and H. influenzae, such as amoxicillin-clavulanate or a respiratory fluoroquinolone 1
   • Investigate bacterial coinfection in patients who deteriorate after initial improvement or fail to improve after 3-5 days of antiviral treatment 1

2. Monitoring for Clinical Deterioration

   • Monitor for worsening symptoms, particularly increasing shortness of breath, recurrent fever, and development of pneumonia 2
   • Consider hospital referral for those with severe symptoms or high-risk features 2

Common Pitfalls and Caveats

1. Delayed Treatment

   • Do not withhold treatment while awaiting test results in suspected cases 1
   • While greatest benefit occurs when treatment is started within 48 hours, treatment may still provide benefit when started later, especially in severely ill or hospitalized patients 7

2. Incomplete Treatment Course

   • The full 5-day course should be completed even if symptoms improve earlier 2

3. Inadequate Dosage Adjustment

   • Failure to adjust oseltamivir dosing in patients with renal impairment can lead to toxicity 2, 3

4. Misunderstanding of Antiviral Role

   • Antivirals are not a substitute for vaccination 3
   • Antibiotics should not be routinely prescribed for uncomplicated influenza 2

5. Resistance Concerns

   • Resistance to oseltamivir is rare (less than 1% overall) and generally of limited clinical significance 4, 7
   • Consider resistance testing in patients who develop influenza while on or immediately after neuraminidase inhibitor prophylaxis 1

By following these evidence-based recommendations, clinicians can effectively manage influenza infections in adults, reducing symptom duration, severity, and risk of complications.