Community-acquired Pneumonia

• See investigation and treatment guidelines in Hospital HealthPathways.
• The CURB-age score stratifies mortality risk with 5 variables (1 point each):

  Confusion (MSQ 8 or less, new disorientation)

  Urea >7 mmol/L

  Respiratory rate of ≥ 30/min

  Blood pressure (systolic < 90 mmHg or diastolic ≤ 60 mmHg)

  -age > 64 years

Pathogens

• Common: Streptococcus pneumoniae
• Other: Haemophilus influenzae, Mycoplasma pneumoniae, Legionella species (notifiable), Staphylococcus aureus, Moraxella catarrhalis, Klebsiella pneumoniae

Drug Treatment

• Consider early switch from IV to oral antimicrobials.
• Duration:
  • Usually 3 to 7 days depending on organism, severity, and antimicrobial choice.
  • Longer treatment courses may be required for M. pneumoniae (7 to 10 days for doxycycline; 5 to 7 days for azithromycin) and Legionella species (5 to 7 days for azithromycin).
  • If M. pneumoniae or Legionella species have not been identified and there are no risk factors for Legionella species, stop azithromycin after 3 days of treatment.

Empiric

Mild Disease (CURB-65 0-1)

amoxicillin HMLSchedNZFPMLnoids Amoxicillin F: 0.9 Half life: 2 hours Elimination: renal fe: 0.9

PO 1000 mg three times a day

• fe = 0.9, consider adjusting dose if CrCl reduced.

If risk factors for Legionella species, add:

azithromycin HMLSchedNZFPML Azithromycin F: 0.4 Half life: 60 hours Elimination: substantial biliary excretion fe: 0.1 Additional points: ↑ warfarin effect.

PO 500 mg once a day

Mild penicillin allergy

cefalexin HMLSchedNZFPML Cefalexin F: 0.9 Half life: 1 hour Elimination: renal fe: 0.9

PO 1000 mg three times day

• fe = 0.9, consider adjusting dose if CrCl is reduced.

If risk factors for Legionella species, add:

Severe penicillin allergy

Consult Infectious Diseases/Clinical Microbiology.

Moderate Disease (CURB-65 2)

• fe = 0.9, consider adjusting dose if CrCl is reduced.

AND

Mild penicillin allergy

cefuroxime HMLSchedNZFPMLnoids Cefuroxime F: 0.4 Half life: 2 hours Elimination: renal fe: 0.9

IV 1.5 g every eight hours then PO 500 mg twice a day

• fe = 0.9, consider adjusting dose if CrCl is reduced.
• Cefuroxime is not funded for this indication on prescription – ask your ward pharmacist to supply on discharge.
• Cefalexin (PO 1000 mg three times a day) is a funded alternative for discharge.

AND

Severe penicillin allergy

vancomycin HMLSchedNZFPMLnoids Amoxicillin+Clavulanic Acid F: 0.9 / 0.5 Half life: 2 hours / 1 hour Elimination: renal fe: 0.9 / 0.5

See dosing guidelines (use high doses).

• fe = 0.9, adjust dose if CrCl reduced.
• Must be given diluted (1 g in at least 200 mL) and slowly (≤ 1000 mg/hour) to minimise infusion reactions.

AND

Severe Disease (CURB-65 3-4)

• fe (amoxicillin) = 0.9, fe (clavulanic acid) = 0.5, consider adjusting dose if CrCl reduced.

AND EITHER

OR

clarithromycin HMLSchedNZFPMLnoids Clarithromycin F: 0.5 Half life: 4 hours Elimination: CYP3A fe: 0.2 Additional points: Inhibits CYP3A and Pgp.

IV 500 mg every twelve hours (for 1 or 2 doses then change to azithromycin PO 500 mg once a day)

• Metabolised by and strongly inhibits CYP3A - multiple drug interactions, and inhibits 2C19. (fe = 0.2).

Mild penicillin allergy

• fe = 0.9, consider adjusting dose if CrCl reduced.
• Cefuroxime is not funded for this indication on prescription – ask your ward pharmacist to supply on discharge.

AND EITHER

OR

• Metabolised by and strongly inhibits CYP3A - multiple drug interactions, and inhibits 2C19. (fe = 0.2).

Severe penicillin allergy or any cephalosporin allergy

Consult Infectious Diseases/Clinical Microbiology.

Extremely Severe Disease (CURB-65 5)

• fe (amoxicillin) = 0.9, fe (clavulanic acid) = 0.5, consider adjusting dose if CrCl reduced.

AND

ciprofloxacin HMLSchedNZFPMLnoids Ciprofloxacin F: 0.7 Half life: 4 hours Elimination: renal fe: 0.5 Additional points: Inhibits CYP1A2 and 3A. Antacids, milk, and enteral feeds ↓ absorption.

IV 400 mg every twelve hours

• fe = 0.5, consider adjusting dose in renal impairment.
• Inhibits CYP1A2 (strong) and 3A.
• Subject to OAT and OATP (transporter) inhibition.

If immunosuppressed, or pre-existing lung disease with increased risk of Pseudomonas species infection:

piperacillin+tazobactam HMLNZFPMLnoids Piperacillin+Tazobactam F: n/a Half life: 1 hour Elimination: renal fe: 0.8/0.6

IV 4 g/500 mg every eight hours

• If still on piperacillin+tazobactam beyond 48 hours, consider measuring a trough concentration. Consult Infectious Diseases for interpretation.
• fe (piperacillin) = 0.8, fe (tazobactam) = 0.6, consider adjusting dose if CrCl reduced.

AND

• fe = 0.5, consider adjusting dose in renal impairment.
• Inhibits CYP1A2 (strong) and 3A.
• Subject to OAT and OATP (transporter) inhibition.

Mild penicillin allergy

Consult Infectious Diseases/Clinical Microbiology.

Severe penicillin allergy

Consult Infectious Diseases/Clinical Microbiology.

Pathogens Known

Most patients should be on oral therapy.

If severe/extremely severe, administer antimicrobials IV except for azithromycin (if stable and able to swallow).

Streptococcus pneumoniae

Amoxicillin susceptible: see CURB-65 2 disease empiric treatment, increasing amoxicillin dosing frequency to every six hours if the MIC is 2 mg/L.

Reduced amoxicillin susceptibility: MIC > 2 mg/L

Consult Infectious Diseases/Clinical Microbiology.

Haemophilus influenzae, Moraxella catarrhalis

• fe = 0.9, consider adjusting dose if CrCl reduced.

If beta-lactamase producing:

• fe (amoxicillin) = 0.9, fe (clavulanic acid) = 0.5, consider adjusting dose if CrCl reduced.

Mild penicillin allergy

• fe = 0.9, consider adjusting dose if CrCl reduced.
• Cefuroxime is not funded for this indication on prescription – ask your ward pharmacist to supply on discharge.

Severe penicillin allergy

Consult Infectious Diseases/Clinical Microbiology.

Staphylococcus aureus

Start antimicrobial therapy as below, and consult with Infectious Diseases/Clinical Microbiology.

flucloxacillin HMLSchedNZFPMLnoids Flucloxacillin F: 0.9 Half life: 1 hour Elimination: renal fe: 0.7

IV 2 g every six hours

• fe = 0.7, consider adjusting dose if CrCl reduced.
• Risk of hepatotoxicity is increased in females, patients > 55 years old, high doses, and courses longer than 14 days duration.

Mild penicillin allergy

cefazolin HMLSchedNZFPMLnoids Cefazolin F: n/a Half life: 2 hours Elimination: renal fe: 0.9

IV 2 g every eight hours

• fe = 0.9, consider adjusting dose if CrCl reduced.

Patients with severe penicillin allergy or MRSA, consult with Infectious Diseases/Clinical Microbiology and consider:

vancomycin HMLSchedNZFPMLnoids Vancomycin F: n/a Half life: 6 hours Elimination: renal fe: 0.9 Additional points: TDM

See dosing guidelines (use high doses).

• fe = 0.9, adjust dose if CrCl reduced.
• Must be given diluted (1 g in at least 200 mL) and slowly (≤ 1000 mg/hour) to minimise infusion reactions.

Klebsiella pneumoniae

ceftriaxone HMLSchedNZFPMLnoids Ceftriaxone F: n/a Half life: 8 hours Elimination: 50% renal and 50% biliary excretion fe: 0.5

IV 2 g every 24 hours

• fe = 0.5, consider adjusting dose if CrCl reduced.
• Check susceptibilities.

Severe penicillin allergy

Consult Infectious Diseases/Clinical Microbiology.

Mycoplasma pneumoniae

Mild or moderate disease

doxycycline HMLSchedNZFPML Doxazosin F: 0.7 Half life: 12 hours Elimination: CYP3A fe: 0.1

PO 100 mg twice a day for 7 to 10 days

• Metabolised by unknown pathways. (fe = 0.4).
• Avoid in pregnancy and breastfeeding.

OR

Severe disease

Consult Infectious Diseases/Clinical Microbiology/Respiratory Medicine.

Legionella species (notifiable)

Topic Code: 99246

must be prescribed or recommended by a consultant.