Acute bacterial rhinosinusitis is the mucosal inflammation of the nose and paransal sinuses caused by bacteria lasting >10 days for up to 4 weeks or symptoms worsening for 5-7 days and is <12 weeks with complete resolution of symptoms.
It is often preceded by a viral upper respiratory tract infection.
Signs and symptoms are nonspecific and typically difficult to differentiate from viral upper respiratory tract infection.
There is fever with nasal obstruction/congestion or anterior and/or posterior purulent drainage, with or without facial pressure/pain/fullness and reduction/loss of smell.
Streptococcus pneumoniae and unencapsulated strains of Haemophilus influenzae cause half of acute rhinosinusitis cases.

Principles of Therapy

General Antibiotic Therapy Principles

  • Empiric therapy should be started as soon as acute bacterial rhinosinusitis (ABRS) is diagnosed
    • Therapy should be based on cost, safety, likely pathogen, local resistance patterns and recent antibiotic use
  • Antibiotic therapy should be started in patients with the following presentations:
    • Severe ABRS: Patient with >3 consecutive days of fever (≥39°C) with purulent nasal discharge or facial pain
    • Worsening ABRS: Presence of increased nasal discharge, headache or new fever after a typical viral URTI of 5-6 days that was initially improving
    • Persistent ABRS: ≥10 days symptoms (nasal discharge of any quality, cough) without signs of improvement
    • Severe, worsening or persistent ABRS with accompanying acute otitis media, pharyngitis, adenitis or pneumonia, or if suspected to have orbital or intracranial involvement
    • Uncomplicated severe, worsening or persistent ABRS without concomitant disease
  • Initial antibiotic prescribed should be the most narrow-spectrum agent that is active against the likely pathogens: S pneumoniae, H influenzae, M catarrhalis
    • Consider the local prevalence of resistance among each of the likely bacterial species
  • Initial empiric therapy coverage for S aureus or methicillin-resistant S aureus is not recommended
  • Factors that predispose patients to antibiotic-resistant bacteria need to be considered (eg antibiotic usage within the past month, hospitalization in the past 5 days, age <2 or >65 years, exposure to daycare, comorbid conditions, impaired immune response, severe infection, living in areas with high rates of resistance)

Goals of Antibiotic Therapy

  • Eradicate bacterial infection from the sinuses
  • Hasten resolution of symptoms
  • Prevent complications
  • Decrease the development of chronic disease


Mild Disease and No Antibiotics Within the Last 4-6 Weeks

  • In patients who have not responded to symptomatic therapy alone or those whose symptoms have worsened

Amoxicillin (Usual or High Dose)

  • Amoxicillin continues to be the agent of choice for ABRS due to its safety, efficacy, low cost and narrow microbiologic spectrum when still effective in the locality
    • Should be taken for 5-10 days
  • In areas with high incidence of resistant S pneumoniae, high-dose Amoxicillin should be considered
  • Generally considered the most active of all oral beta-lactams against streptococci and only S pneumoniae that is highly resistant to Penicillin will not respond to conventional doses of Amoxicillin
    • Activity against beta-lactamase-negative strains of H influenzae is fair to good but it is ineffective against beta-lactamase-producing strains

Amoxicillin/Clavulanic Acid with or without High-Dose Amoxicillin

  • Recommended as initial empiric therapy for ABRS rather than Amoxicillin alone
  • Recommended in patients with moderate to severe disease who have failed high-dose Amoxicillin or if beta-lactamase-producing strains of H influenzae, M catarrhalis or oral anaerobes are suspected
  • Amoxicillin may be added to Amoxicillin/clavulanic acid to overcome drug resistance of S pneumoniae and should be considered in areas with high incidence of resistant S pneumoniae

Cephalosporins (2nd and 3rd Generation)

  • Eg Cefaclor, Cefdinir, Cefixime, Cefuroxime, Cefpodoxime, Ceftriaxone
  • Alternative agents that may be considered for patients with ABRS who have non-type 1 allergy to Penicillin
    • Because of variable resistance to S pneumoniae, it is not recommended for single-agent empiric therapy
    • Local resistance patterns and antimicrobial spectrum of the cephalosporins to S pneumoniae, H influenzae and M catarrhalis will need to be considered prior to choosing an agent
  • Cefaclor has poor overall efficacy against bacterial respiratory tract pathogens
  • Cefixime has potent activity against H influenzae
  • Cefpodoxime is the preferred agent for patients with treatment failure on high-dose Amoxicillin or Amoxicillin/clavulanic acid
    • Has similar activity with Cefuroxime and Cefdinir against S pneumoniae but greater efficacy against H influenzae
  • Cefuroxime has good efficacy against S pneumoniae but less active than Cefpodoxime against H influenzae
  • Intravenous/intramuscular Ceftriaxone (50 mg/kg single-dose) may be considered for patients intolerant to oral medications and highly unlikely to adhere to prescribed medications


  • Depending on the sensitivity pattern of local isolates, Co-trimoxazole may be considered an alternative for patients with type 1 allergy to Penicillin
    • Not advised for empiric therapy due to increased rates of resistance to both S pneumoniae and H influenzae


  • Alternative agent to Amoxicillin or Amoxicillin/clavulanic acid in initial empiric therapy or to those who have type 1 allergy to Penicillin
  • Doxycycline has activity against Penicillin-susceptible pneumococci and M catarrhalis, but limited coverage for H influenzae
    • The probability of non-susceptibility to Doxycycline tends to rise in pneumococcal strains that have any level of Penicillin resistance


  • These agents may be considered alternatives in patients who have type 1 allergy to Penicillin
  • All macrolides have good activity against macrolide-susceptible pneumococci but are not recommended for empiric therapy because of increasing prevalence of macrolide-resistant S pneumoniae
  • Azithromycin and Clarithromycin are relatively weak against penicillin-resistant H influenzae and S pneumoniae

Moderate-Severe Disease or Antibiotics Received Within the Last 4-6 Weeks

  • Patients who failed 1st-line therapy may be considered with this group of patients

Amoxicillin/Clavulanic Acid with High Dose-Amoxicillin

  • Considered 1st-line agent by many authorities for patients who have failed Amoxicillin or in those with risk for resistant organisms
  • Therapy should be initiated using higher doses of Amoxicillin (add Amoxicillin therapy to Amoxicillin/clavulanic acid); this will increase the coverage of S pneumoniae


  • 5-day therapy may be considered in those at risk for resistant organisms or in those who have failed 1st-line therapy

Respiratory Quinolones

  • Eg Levofloxacin, Moxifloxacin
  • Provide excellent coverage for all the likely pathogens, especially S pneumoniae and H influenzae
  • Because of the potential for increased resistance and toxicity, these agents should be reserved for adults with type 1 allergy to Penicillin and risk factors for resistant organisms, moderate disease, or in those who have failed recent antibiotic coverage

Combination Therapy

  • Eg Cefixime + high-dose Amoxicillin or Clindamycin or Rifampicin + high-dose Amoxicillin or Clindamycin
  • Combination therapy that has adequate Gram-positive and negative coverage may be considered in patients with risk of resistant organisms, moderate disease or have failed 1st-line therapy
  • At this time, there is no clinical evidence supporting the use or safety of combination therapy but it is recommended based on in vitro spectrum activity
  • Rifampicin + Clindamycin
    • Rifampicin should not be used as monotherapy or for longer than 10-14 days because resistance develops rapidly to this agent
  • Clindamycin/Linezolid + Cefixime
    • Recommended for patients with severe type 1 Penicillin hypersensitivity with moderate-severe sinusitis

Duration of Antibiotic Therapy

  • The appropriate duration of antibiotic therapy is not well defined
  • Most patients with ABRS that have been treated with the appropriate antibiotic agent will show clinical improvement within 48-72 hours
  • If ABRS is worse within 72 hours after initiating treatment:
    • If initially advised further observation, may start Amoxicillin with or without Clavulanate therapy
    • If initially prescribed with Amoxicillin, may increase dose and may add Clavulanate
    • If initially prescribed with high-dose Amoxicillin-Clavulanate, may shift to Clindamycin + Cefixime OR Linezolid + Cefixime OR Levofloxacin
  • No clinical improvement seen after 72 hours:
    • If initially advised further observation, may start antibiotic therapy
    • If initially prescribed with Amoxicillin, may initiate high-dose Amoxicillin/Clavulanate therapy
    • If initially prescribed with high-dose Amoxicillin-Clavulanate, may continue giving high dose Amoxicillin-Clavulanate OR may shift to Clindamycin + Cefixime OR Linezolid + Cefixime OR Levofloxacin
  • In patients without severe ABRS and comorbidities, they may benefit from short-course treatment which leads to better compliance, fewer adverse effects, lower resistance rates and lower costs of medications
  • Short-course treatment with appropriate oral antibiotic treatment is given in 7 days
    • May be extended to 14 days if symptoms fail to resolve
  • The duration of antibiotic therapy in patients with moderate to severe ABRS is 7 to 14 days
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