Management of Community-Acquired Pneumonia

Abstract

In patients with community-acquired pneumonia (CAP), it is uncommon for the causative pathogen to be identified when initial antimicrobial therapy is prescribed. Thus, an empirical approach is generally taken, based on antimicrobial therapy which covers the major pathogens of CAP. Although Streptococcus pneumoniae remains the most common pathogen in microbiologically documented CAP, atypical pathogens now account collectively for approximately 10 to 40% of episodes. Accordingly, North American guidelines recommend macrolides as one of the preferred choices in patients with mild to severe CAP, as monotherapy in those who can be treated as outpatients and as part of combination therapy for more severely ill patients. It should be noted that macrolides are not recommended when drug-resistant pneumococcal infection or aspiration is suspected. Expanded-spectrum fluoroquinolones are likely to assume an increased role in areas with high rates of drug-resistant pneumococci. Where the pathogen is known, macrolides are a reasonable choice in CAP caused by atypical pathogens and an alternative therapy for penicillin-susceptible S. pneumoniae or M. catarrhalis infection. Clarithromycin has good in vitro activity against most respiratory pathogens, including the atypical pathogens Chlamydia pneumoniae, Mycoplasma pneumoniae and Legionella spp. Clarithromycin has similar efficacy to erythromycin in adults and children with mild to moderate CAP but is better tolerated. Also, it is given in a once (delayed-release formulation) or twice daily dosage schedule, which may encourage patient compliance. As with erythromycin, clarithromycin interacts with a wide range of drugs metabolised by the CYP450 system, which limits its usefulness in patients receiving other therapies. Other newer macrolides also offer advantages over erythromycin, so all factors should be considered when selecting such an agent for treatment. Although clarithromycin, like other newer macrolides, is generally more costly than erythromycin in terms of acquisition costs, it may well be more cost effective when other factors (e.g. better tolerability, fewer daily doses) are taken into account. Conclusions: Oral clarithromycin has several features which make it an attractive treatment option for patients with mild to moderate CAP. It offers some clear advantages over erythromycin in terms of potential pharmacoeconomic benefits, reduced number of daily doses and its tolerability profile. As with other macrolides, it has a particular role in empirical use in areas without high rates of pneumococcal resistance and as targeted therapy in those with documented or suspected atypical pneumonia.