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Acute Bacterial Rhinosinusitis (ABRS)

URI / Outpatient

Source: IDMP View on spectrum chart →
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1. Clinical Syndrome

Bacterial infection of the paranasal sinuses, typically a secondary complication of viral URI. Distinguishing bacterial from viral requires duration + severity criteria:

  • Persistent (≥10 d without improvement) — most common bacterial pattern,
  • Severe at onset (T ≥39 + purulent nasal discharge + facial pain ≥3–4 consecutive days), or
  • Double-sickening (initial improvement of viral URI, then worsening with new fever + facial pain).

Excludes: viral sinusitis / common cold (<10 d, improving) — no antibiotics. Chronic rhinosinusitis (>12 wk — separate workflow, often biofilm-mediated, refer ENT). Allergic rhinitis (chronic, bilateral, sneezing, itch — antihistamines / nasal steroids). Fungal sinusitis (invasive in immunocompromised — see mucormycosis; allergic fungal in atopic — surgery + steroids).

2. Pathogens

Consider the patient: Adults more often than children with this presentation. Recent URI, allergic rhinitis, smoking, dental infection (esp. maxillary sinus), immunocompromise (consider fungal — emergent).

Consider the case: Most acute sinusitis is viral (>98%). Use the duration + severity criteria above. Imaging not needed for uncomplicated ABRS. CT head + sinuses only if orbital / intracranial complication suspected (proptosis, vision change, severe HA, AMS) or refractory case.

Common

Less common

3. Empiric Therapy

TierFirst choiceAlternativesDurationComments
Outpatient
  • 875 mg / 125 mg · PO BID (or 2000/125 mg ER BID for severe / risk) · PO · 5–7 days (adult) or 10–14 days (children)

    **First-line per IDSA 2012** — covers β-lactamase H. flu + M. catarrhalis better than amoxicillin alone.

  • 100 mg PO BID or 200 mg daily · PO daily · PO · 5–7 days

    PCN-allergic adult; good pneumococcal + H. flu coverage.

  • 500 mg · PO daily · PO · 5–7 days

    Reserve for severe PCN allergy + doxycycline intolerance. Avoid as first-line — FDA black-box (tendon rupture, dysglycemia, peripheral neuropathy, aortic dissection).

  • 400 mg · PO daily · PO · 5–7 days

    Same caveats as levofloxacin.

  • 1 g · PO TID (or 875 mg BID) · PO · 5–7 days

    IDSA recommends amox-clav OVER amox alone given β-lactamase prevalence — use amox alone only if low local β-lactamase rate.

5–7 days adults; 10–14 days children**Add high-dose amox-clav (2000/125 ER BID)** when concerned about PRSP: severe symptoms, prior antibiotics in 4–6 wk, age >65, immunocompromised, daycare exposure (peds). **Treat symptoms** with saline irrigation, intranasal steroids, analgesics. Decongestants short-term.

4. Directed Therapy

Treatment failure (no improvement at 3–5 d or worsening at any time):

  • Switch to high-dose amox-clav (2000/125 ER BID) if not already.
  • Or doxycycline if PCN-treated.
  • Or levofloxacin/moxifloxacin as last resort PO.
  • Consider CT sinuses + ENT referral.
  • Consider culture via endoscopic-guided aspirate (ENT) — rare in outpatient practice.

Orbital / intracranial complications (orbital cellulitis / abscess, cavernous sinus thrombosis, subdural empyema, meningitis): admit, IV vancomycin + ceftriaxone + metronidazole, CT/MRI, ENT + neurosurgery consult, drainage of abscess.

Invasive fungal sinusitis (immunocompromised — mucormycosis, invasive aspergillosis): emergent ENT consult, debridement, IV amphotericin / isavuconazole, see mucormycosis / invasive-aspergillosis syndromes.

5. Monitoring

Reassess at 5 d — clinical improvement (less fever, less facial pain) expected; no improvement → escalate or imaging.

Saline irrigation + nasal steroid spray adjuncts have moderate evidence and minimal harm. Decongestants short-term (<3 d topical, ≤7 d oral) — rebound congestion otherwise.

Toxicity: amox-clav diarrhea (very common; give with food, probiotic helpful, expect mild). Doxycycline esophagitis + photosensitivity. Fluoroquinolone black-box risks.

Pearls

Most sinusitis is viral — antibiotics for persistent ≥10 d, severe onset, or double-sickening only. Amox-clav is first-line (not amox alone in current US epidemiology). Watchful waiting acceptable. Imaging not needed for uncomplicated. Macrolides + tmp-smx fail — high pneumococcal resistance. Fluoroquinolones last resort given black-box. Orbital complications = admit + IV + imaging + ENT/neurosurgery.

References