Pharmaceutical Regimen for Positive Influenza
The recommended first-line treatment for patients with positive influenza is oseltamivir (Tamiflu) 75 mg twice daily for 5 days in adults, with weight-based dosing for children, initiated as soon as possible and ideally within 48 hours of symptom onset. 1, 2
Antiviral Treatment Options
Oseltamivir (First-line)
- Adults: 75 mg twice daily for 5 days
- Children ≥12 months (weight-based):
- <15 kg: 30 mg twice daily
- 15-23 kg: 45 mg twice daily
- 23-40 kg: 60 mg twice daily
40 kg: 75 mg twice daily
- Infants 9-11 months: 3.5 mg/kg per dose, twice daily
- Term infants 0-8 months: 3 mg/kg per dose, twice daily
- Preterm infants (postmenstrual age):
- <38 weeks: 1.0 mg/kg per dose, twice daily
- 38-40 weeks: 1.5 mg/kg per dose, twice daily
40 weeks: 3.0 mg/kg per dose, twice daily
Alternative Antivirals
Zanamivir (Relenza):
- 10 mg (two 5-mg inhalations) twice daily for 5 days
- For ages ≥7 years for treatment
- Important limitation: Not recommended for patients with underlying airways disease (asthma, COPD) due to risk of bronchospasm 3
Peramivir (IV option):
- Adults: One 600-mg IV infusion over 15-30 minutes
- Children (2-12 years): 12 mg/kg (up to 600 mg maximum) IV infusion
- Children (13-17 years): 600 mg IV infusion
Baloxavir:
- For people ≥12 years who weigh >40 kg
- 40-80 kg: one 40-mg single dose
80 kg: one 80-mg single dose
Timing Considerations
The timing of antiviral initiation is critical for maximizing efficacy:
- Treatment should begin within 48 hours of symptom onset 2
- Earlier treatment provides significantly greater benefits:
Special Populations
Renal Impairment
- For patients with creatinine clearance 10-30 mL/min: Reduce oseltamivir to 75 mg once daily for 5 days 1
Immunocompromised or Severely Ill Patients
- May benefit from treatment even if started >48 hours after symptom onset 2
- May benefit from treatment even without documented fever 2
Patients with Respiratory Disease
- Oseltamivir is preferred over zanamivir for patients with underlying respiratory disorders 3
- Zanamivir should be avoided in patients with asthma or COPD due to risk of bronchospasm 3
Antibiotic Considerations
Antibiotics are not routinely indicated for uncomplicated influenza but should be considered in specific situations:
- Patients with worsening symptoms (recrudescent fever or increasing dyspnea) 1, 2
- High-risk patients with lower respiratory features 1
- Patients with evidence of secondary bacterial infection 1
When antibiotics are indicated:
- First-line: Co-amoxiclav or a tetracycline 1, 2
- Alternative (for penicillin allergy): Macrolide (clarithromycin) or respiratory fluoroquinolone 1
Practical Considerations
- Oseltamivir can be taken with or without food, but taking with food may improve gastrointestinal tolerability 1
- Approximately 10% of patients may experience transient nausea or vomiting, typically resolving within 1-2 days 4
- For patients scheduled to use an inhaled bronchodilator at the same time as zanamivir, the bronchodilator should be used before zanamivir 3
Common Pitfalls to Avoid
Delaying treatment: Efficacy decreases significantly with delayed initiation. Do not wait for laboratory confirmation before starting treatment in high-risk patients during influenza season.
Inappropriate use of zanamivir: Avoid prescribing zanamivir for patients with underlying respiratory conditions due to risk of bronchospasm.
Unnecessary antibiotic use: Antibiotics should not be prescribed routinely for uncomplicated influenza without evidence of bacterial co-infection.
Inadequate dose adjustment: Failing to adjust oseltamivir dosing in patients with renal impairment can lead to toxicity.
Stopping treatment prematurely: The full 5-day course should be completed even if symptoms improve earlier.