In an otherwise healthy adult or adolescent presenting with signs of acute bacterial sinusitis, streptococcal pharyngitis, or acute bacterial otitis media, what are the recommended first‑line antibiotic regimens and supportive measures?

First-Line Antibiotic Regimens and Supportive Measures for Bacterial Upper Respiratory Infections in Healthy Adults and Adolescents

Acute Bacterial Sinusitis

When to Prescribe Antibiotics (Not Before)

Antibiotics are indicated only when acute bacterial rhinosinusitis is confirmed by at least one of three patterns: persistent symptoms ≥10 days without improvement (purulent nasal discharge plus obstruction or facial pain/pressure), severe symptoms ≥3–4 consecutive days with fever ≥39°C plus purulent discharge and facial pain, or "double sickening" (initial improvement followed by worsening). 12 Approximately 98–99.5% of acute rhinosinusitis is viral and resolves spontaneously within 7–10 days without antibiotics. 12

First-Line Antibiotic Choice

Amoxicillin-clavulanate 875 mg/125 mg twice daily for 5–10 days is the preferred first-line regimen, providing 90–92% predicted clinical efficacy against Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. 2 The clavulanate component is essential because 30–40% of H. influenzae and 90–100% of Moraxella catarrhalis produce β-lactamase. 2

For patients with recent antibiotic use (past 4–6 weeks), age >65 years, daycare exposure, moderate-to-severe symptoms, or comorbidities, use high-dose amoxicillin-clavulanate 2 g/125 mg twice daily. 2

Treatment Duration

Continue therapy for 5–10 days or until symptom-free for 7 consecutive days (typically 10–14 days total). 2 Recent evidence supports 5–7 day courses as equally effective with fewer adverse effects. 2

Alternatives for Penicillin Allergy

• Non-severe (non-type I) allergy: Second- or third-generation cephalosporins (cefuroxime-axetil, cefpodoxime-proxetil, cefdinir, cefprozil) for 10 days—cross-reactivity is negligible. 2
• Severe (type I/anaphylactic) allergy: Respiratory fluoroquinolones—levofloxacin 500 mg once daily for 10–14 days or moxifloxacin 400 mg once daily for 10 days—provide 90–92% predicted efficacy. 2
• Doxycycline 100 mg once daily for 10 days is acceptable but suboptimal (77–81% efficacy with 20–25% bacteriologic failure rate). 2

Essential Adjunctive Therapies (Add to All Patients)

• Intranasal corticosteroids (mometasone, fluticasone, or budesonide) twice daily significantly reduce mucosal inflammation and accelerate symptom resolution—supported by strong evidence from multiple randomized controlled trials. 2
• Saline nasal irrigation 2–3 times daily for symptomatic relief and mucus clearance. 2
• Analgesics (acetaminophen or ibuprofen) for pain and fever control. 2

Monitoring and Reassessment

Reassess at 3–5 days: If no improvement (persistent purulent drainage, unchanged facial pain, or worsening), switch immediately to high-dose amoxicillin-clavulanate or a respiratory fluoroquinolone. 2

Reassess at 7 days: Persistent or worsening symptoms warrant diagnostic reconsideration, exclusion of complications (orbital cellulitis, meningitis), and possible imaging or ENT referral. 2

Critical Pitfalls to Avoid

• Do not prescribe antibiotics for symptoms <10 days unless severe features (fever ≥39°C with purulent discharge for ≥3 consecutive days) are present. 12
• Avoid macrolides (azithromycin) due to 20–25% resistance rates in S. pneumoniae and H. influenzae. 2
• Avoid trimethoprim-sulfamethoxazole due to 50% resistance in S. pneumoniae and 27% in H. influenzae. 2
• Avoid first-generation cephalosporins (cephalexin) due to inadequate coverage against H. influenzae (≈50% produce β-lactamase). 2

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Streptococcal Pharyngitis

Testing Before Treatment

Antibiotics should only be prescribed for adults with confirmed streptococcal pharyngitis by positive rapid antigen detection test (RADT) or throat culture. 13 Only 5–15% of adult pharyngitis cases are caused by Group A Streptococcus, yet >60% receive antibiotics—representing massive overtreatment. 3

Use Centor criteria (fever by history, tonsillar exudates, tender anterior cervical adenopathy, absence of cough) to identify patients needing testing: those with <3 criteria do not need testing; those with ≥3 criteria should undergo RADT. 1 Negative RADT does not require confirmatory throat culture in adults due to low rheumatic fever risk. 3

First-Line Antibiotic Choice

Penicillin or amoxicillin for 10 days is the first-line treatment to eradicate Group A Streptococcus from the pharynx and prevent acute rheumatic fever. 13 Specific regimens include penicillin V potassium 500 mg twice daily or amoxicillin 500 mg twice daily for 10 days. 1

Alternatives for Penicillin Allergy

For documented penicillin allergy, use cephalosporins (cefuroxime, cefpodoxime, cefdinir) or macrolides (azithromycin, clarithromycin) as alternatives. 145 However, note that macrolides have higher resistance rates for sinusitis pathogens.

Symptomatic Management (For All Patients)

Every adult with pharyngitis should receive appropriate symptomatic care regardless of etiology: NSAIDs or acetaminophen for pain and fever, throat lozenges, and salt water gargles. 13 Reassure patients that typical pharyngitis resolves in <1 week. 3

Clinical Benefits of Antibiotics

Antibiotics shorten symptom duration by only 1–2 days, with a number needed to treat of 6 after 3 days and 21 after 1 week—indicating modest benefit. 13 The primary justification is preventing complications (peritonsillar abscess, spread to contacts, acute rheumatic fever), though rheumatic fever risk is extremely low in adults. 13

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Acute Bacterial Otitis Media (Adolescents/Adults)

First-Line Antibiotic Choice

High-dose amoxicillin 80–90 mg/kg/day (or amoxicillin-clavulanate for areas with high resistant S. pneumoniae prevalence) is the first-line treatment for acute otitis media. 12 For adolescents and adults, standard dosing is amoxicillin 500 mg twice daily (mild disease) or 875 mg twice daily (moderate disease). 2

Treatment Duration

Standard duration is 10 days for acute otitis media to ensure eradication and prevent complications. 12

Alternatives for Treatment Failure

If no improvement after 72 hours, switch to high-dose amoxicillin-clavulanate or a second-line agent (ceftriaxone 50 mg/kg IM as single dose for children unable to tolerate oral medications). 12

Adjunctive Therapies

Analgesics (acetaminophen or ibuprofen) for pain control are essential. 1 Intranasal corticosteroids may provide benefit as adjunctive therapy. 1

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Key Principles Across All Three Conditions

Watchful Waiting Option

For uncomplicated acute bacterial sinusitis with reliable follow-up, initial observation without antibiotics is appropriate; initiate antibiotics only if no improvement by day 7 or if symptoms worsen at any time. 2 The number needed to treat with antibiotics is 10–15 to achieve one additional cure. 2

When to Refer to Specialist

Refer to otolaryngology or infectious disease if: no improvement after 7 days of appropriate second-line antibiotics, worsening symptoms at any point, suspected complications (orbital cellulitis, meningitis, intracranial abscess), or recurrent infections (≥3 episodes per year) requiring evaluation for underlying allergic rhinitis, immunodeficiency, or anatomic abnormalities. 12

Antibiotic Stewardship

Reserve fluoroquinolones for second-line therapy or severe penicillin allergy to prevent resistance development; do not use as routine first-line in patients without documented β-lactam allergy. 2 Ensure adequate treatment duration (minimum 5 days for adults with sinusitis, 10 days for pharyngitis and otitis media) to prevent relapse. 23