What is the recommended treatment for a typical adult patient with flu symptoms, particularly those with underlying health conditions or severe symptoms?

Treatment of Influenza in Adults

For adults with flu symptoms, initiate oseltamivir 75 mg orally twice daily for 5 days if presenting within 48 hours of symptom onset, with fever >38°C, and acute influenza-like illness—but extend this treatment window to severely ill, hospitalized, or high-risk patients regardless of symptom duration. 1, 2

Antiviral Therapy: The Foundation of Treatment

Standard Dosing and Timing

• Oseltamivir 75 mg orally twice daily for 5 days is the treatment of choice for confirmed or clinically suspected influenza 1, 2
• Ideally start within 48 hours of symptom onset for maximum benefit, reducing illness duration by approximately 24-36 hours and symptom severity by up to 38% 1, 3, 4
• Taking oseltamivir with food enhances tolerability and reduces nausea (occurs in ~10% of patients) 1, 2, 3

Critical Exception: Treatment Beyond 48 Hours

Do not withhold oseltamivir based solely on timing if the patient meets any of these criteria:

• Hospitalized or severely ill patients should receive treatment at any point in their illness, as viral replication may continue and benefit is still possible 1, 5
• High-risk patients including those with COPD, heart disease, diabetes, immunosuppression, or age >65 years warrant treatment even beyond 48 hours 1, 6, 5
• Immunocompromised or elderly patients who cannot mount adequate fever response may benefit despite lack of documented fever 1, 5

Renal Dosing Adjustment

• Reduce dose to 75 mg once daily if creatinine clearance <30 mL/minute 1, 2

Antibiotic Management: When and What to Prescribe

Uncomplicated Influenza (No Pneumonia)

Antibiotics are NOT routinely indicated for previously healthy adults with uncomplicated influenza or acute bronchitis 1, 7

When to Consider Antibiotics

Strongly consider antibiotic therapy in these scenarios:

• Worsening symptoms after initial presentation, particularly recrudescent fever or increasing breathlessness, suggesting bacterial superinfection 1, 6
• High-risk patients (COPD, chronic heart disease, diabetes) with lower respiratory tract features should receive empiric antibiotics 1
• Clinical evidence of pneumonia on examination or imaging warrants immediate antibiotic treatment 1

First-Line Antibiotic Choices

For community management:

• Co-amoxiclav (amoxicillin-clavulanate) 625 mg three times daily OR doxycycline 200 mg loading dose, then 100 mg once daily for 7 days 1
• These cover the most common bacterial superinfections: Streptococcus pneumoniae, Staphylococcus aureus, and Haemophilus influenzae 1, 6
• Alternative: Clarithromycin 500 mg twice daily (preferred over azithromycin for better H. influenzae coverage) for penicillin-allergic patients 1

For hospitalized patients with severe pneumonia:

• Intravenous co-amoxiclav OR cefuroxime/cefotaxime PLUS clarithromycin or erythromycin to cover atypical pathogens and S. aureus 1
• Administer antibiotics within 4 hours of admission if pneumonia is confirmed 1

Risk Stratification: Who Needs Closer Monitoring or Hospitalization?

High-Risk Populations Requiring Lower Threshold for Treatment

• Age >65 years (may present without fever or with atypical symptoms) 6, 5
• Chronic medical conditions: COPD, heart disease, diabetes, immunosuppression 1, 6
• Pregnant women 5

Hospitalization Criteria

Consider admission if ≥2 of the following are present:

• Temperature >37.8°C 1, 6
• Heart rate >100/min 1, 6
• Respiratory rate >24/min 1, 6
• Systolic blood pressure <90 mmHg 1, 6
• Oxygen saturation <90% 1, 6
• Inability to maintain oral intake 1, 6
• Altered mental status 1, 6

Common Pitfalls and How to Avoid Them

Pitfall 1: Withholding Oseltamivir After 48 Hours in Severe Cases

The 48-hour window is for otherwise healthy outpatients. Severely ill, hospitalized, or high-risk patients benefit from treatment at any point in their illness 1, 5, 8

Pitfall 2: Prescribing Antibiotics for Uncomplicated Influenza

Resist the urge to prescribe antibiotics reflexively. Previously healthy adults with cough, sputum, and wheeze but no pneumonia do not need antibiotics 1, 7. Consider a delayed antibiotic prescription with instructions to use only if symptoms worsen or fail to improve after 2 days 1

Pitfall 3: Using Double-Dose Oseltamivir

Do not prescribe 150 mg twice daily. No additional benefit has been demonstrated, and standard dosing (75 mg twice daily) is sufficient even in severe cases 5, 8

Pitfall 4: Missing Renal Dose Adjustment

Always check creatinine clearance in elderly patients or those with known renal impairment, as failure to adjust can lead to toxicity 1, 2

Pitfall 5: Prescribing Zanamivir to Patients with Asthma or COPD

Avoid inhaled zanamivir in patients with underlying airways disease due to bronchospasm risk; oseltamivir is the safer choice 5

Expected Clinical Course and When to Reassess

Typical Fever Duration

• Uncomplicated influenza: Fever lasts 3-5 days 6
• Fever persisting beyond 6 days warrants evaluation for complications, particularly bacterial superinfection or pneumonia 6

Red Flags for Bacterial Superinfection

• Recrudescent fever (fever returns after initial improvement) 1, 6
• Increasing breathlessness or dyspnea 1, 6, 7
• New focal chest signs suggesting pneumonia 1, 7