What Is the Best Outpatient Treatment for CAP in Adults?


ATS and IDSA update clinical practice guidelines for community-acquired pneumonia.

About 1 million adults in the United States are hospitalized for pneumonia every year, and 50,000 die from this disease.1

Half of all immunocompetent adults hospitalized for severe pneumonia in the United States are between 18 and 57 years of age).1In the United States, pneumonia is 1 of the top ten most expensive conditions seen during inpatient hospitalizations. In 2013, pneumonia had an aggregate cost of nearly $9.5 billion for 960,000 hospital stays.1

The American Thoracic Society (ATS) and the Infectious Disease Society of America (IDSA) recently updated clinical practice guidelines previously published in 2007.2The guidelines focus on patients in the United States who are not immunocompromised and have not recently traveled abroad.

Antibiotic recommendations for the treatment of community-acquired pneumonia (CAP) include coverage for the traditional pathogensChlamydia pneumonia, Haemophilus influenza, Legionella, Moraxella catarrhalis, Mycoplasma pneumonia, Staphylococcus aureus,andStreptococcus pneumonia.Widespread use of the pneumococcal conjugate vaccine has caused changes in the microbial etiology of CAP. There has been an increase in other etiologic agents including virusesMethicillin Resistant S. Aureus(MRSA) andPseudomonas aeruginosa.

The following recommendations were published by the ATS and IDSA in October 2019 for the management of CAP:2

  1. Sputum gram stain and cultures are not recommended in adults with CAP managed in an outpatient setting.
  2. Blood cultures are not recommended in adults with CAP managed in an outpatient setting.
  3. Routine testing urine forPneumococcusorLegionellais not recommended.
  4. If influenza is circulating in the community, testing with rapid molecular assay rather than an antigen test is recommended.
  5. Serum procalcitonin levels are not recommended to determine the need for initial empiric antibiotic therapy.
  6. When deciding the need for hospitalization, clinical judgment plus the results of a validated prognostic tool should be used. The Pneumonia Severity Index (mdcalc.com/psi-port-score-pneumonia-severity-index-cap) is recommended over the CURB-65 (mdcalc.com/curb-65-score-pneumonia-severity).
  7. Corticosteroids are not recommended routinely in adults with nonsevere or severe CAP.
  8. Patients should be treated with antibiotics for at least 5 days and 7 days for MRSA orPseudomonas. The duration should be guided by validated measures of clinical stability, including ability to eat, blood pressure, heart rate, normal mentation, oxygen saturation, respiratory rate, and temperature.
  9. In adults whose CAP symptoms resolve within 5 to 7 days, follow-up chest imaging does not have to be obtained.

Here are antibiotic treatment regimens for CAP in adults in an outpatient setting:2

1. Outpatient adults with comorbidities, such as alcohol; asplenia; chronic heart, lung, liver, or renal disease; or diabetes.

  • Beta-lactam: amoxicillin/clavulanate, 500 mg/125 mg or 875 mg/125 mg, twice a day, or 2,000 mg/125 mg, twice a day


  • Cephalosporin (cefpodoxime, 200 mg, twice a day, or cefuroxime axetil, 500 mg, twice a day)


  • Macrolide (azithromycin, 500 mg x1, then 250 mg x5, or clarithromycin, 500 mg, twice a day, or 1000 mg (extended-release) x1)


  • Doxycycline, 100 mg, twice a day (less data). Consider a loading dose of 200 mg.


  • Monotherapy with a respiratory quinolone (levofloxacin, 750 mg QD, Moxifloxcin 400 mg, daily, Gemifloxacin 320 md, daily

2. Previously healthy adults without comorbidities or risk factors for antibiotic-resistant pathogens:

  • Amoxicillin, 1 g, 3 times a day (higher doses target resistantStreptococcus pneumonia) OR

  • Doxycycline, 100 mg, twice a day (less data). Consider a loading dose of 200 mg.


  • A macrolide: azithromycin, 500 mg x1, then 250 mg x5, or clarithromycin, 500 mg, twice a day, or 1000 mg (extended-release) x 1 (if local pneumococcal resistance is < 25%) Resistance in most of the United States is > 30%.


The evidence-based clinical practice guidelines were published to help clinicians optimize the care for patients with CAP based on new data. Antimicrobial therapy should be based on the presence of comorbidities and local resistance patterns. These recommendations delineate minimum clinical standard of care but were not developed to obviate the need for clinical observation.

Jean Covino, DHSc, MPA, PA-C, is a clinical professor and director of didactic education at the Pace University-Lenox Hill Hospital PA Program-NYC in New York, New York.Jennifer Hofmann, MS, PA-C, is an associate clinical professor at the Pace University-Lenox Hill Hospital PA Program-NYC.


  1. Top 20 Pneumonia Facts — 2018. American Thoracic Society website.thoracic.org/patients/patient-resources/resources/top-pneumonia-facts.pdf. Accessed November 21, 2019.
  2. Metlay JP, Waterer GW, Long AC, et al. Diagnosis and treatment of adults with community-acquired pneumonia. An official clinical practice guideline of the American Thoracic Society and Infectious Diseases Society of America.American Journal of Respiratory and Critical Care Medicine. 2019;200(7): e45-e67. doi: 10.1164/rccm.201908-1581ST.

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