Antibiotic Therapy in Community-Acquired Pneumonia: Switch and Step Down Therapy

Hugh A. Cassiere, MD, Winthrop University Hospital


Medscape General Medicine. 1998;1(3) 

In This Article

Factors that Influence Antimicrobial Therapy

Several factors influence the choice of antibiotics and the decision concerning if or when to switch from intravenous to oral antibiotics in the course of managing patients with community-acquired pneumonia. These factors include: patient influences, pathogen characteristics, and antibiotic properties.

Patient factors that traditionally influence antibiotic decisions include: the severity of illness;[1,15,16,17,18,19] patient age;[20,21] comorbid medical illness; mental status or vital sign abnormalities;[22] both pulmonary and nonpulmonary organ dysfunction; laboratory abnormalities,[23] such as white blood cell count, arterial blood gas abnormalities, elevated blood urea nitrogen levels, and bacteremia; and radiographic findings, such as parapneumonic effusion and/or abscess formation. Multilobar infiltrates or radiographic progression must also be taken into account in making this decision.

Pathogen characteristics that have an impact on the route and duration of antibiotic therapy include virulence and resistance patterns, and whether the pathogen is intracellular or extracellular. For example, a virulent and resistant pathogen causing community-acquired pneumonia, such as methicillin-resistant Staphylococcus aureus (MRSA), acquired in a nursing homes, usually necessitates a more prolonged course of intravenous antibiotics as compared to pneumonia caused by the less virulent and more antibiotic sensitive Mycoplasma pneumoniae.

Antibiotic properties that allow initiation of switch therapy include dosing schedule, bioavailability, patient tolerance, and cost -- all of which influence compliance. It is also important that an oral agent with the appropriate antimicrobial spectrum is available. An ideal oral antibiotic for switch therapy would have: (1) antimicrobial coverage identical to the intravenous agent, (2) once or twice a day dosing to improve compliance,[24] (3) high level of bioavailability, (4) no adverse side effects, and (5) low acquisition cost.