Erythromycin has been a mainstay of outpatient therapy for many years. Initially used primarily as an alternative to penicillins in those that are allergic, they have had large increases in use because of their activity against “atypical” respiratory pathogens and because of the relatively recent additions clarithromycin (Biaxin®) and azithromycin (Zithromax®) were very actively marketed by their manufacturers. The “new macrolides” tend to cause less GI upset than erythromycin. However, erythromycin is the drug of choice in this class for those who can tolerate it because it is effective and very inexpensive.
The macrolides tend to be very safe, with severe adverse events seen rarely. They have little utility for therapy of hospital-acquired infections. It is for this reason that the misuse or overuse of macrolides for community infections is more tolerable than the misuse or overuse of fluoroquinolones – their major competitors in the huge market of outpatient respiratory tract infection therapy.
An old antibiotic related to the macrolides (clindamycin is technically a lincosamide) that has made a “comeback” because of its utility in severe soft-tissue infections in particular group A Streptococcal necrotizing fasciitis. It is a very useful alternate agent for therapy of S.aureus infections including many MRSA strains and has considerable anti-anaerobic activity making it popular for GI, gynecologic and mouth related infections.
One major drawback to this agent is its propensity to precipitate C. difficile associated disease at a rate higher than any other antibiotic. It must be used with caution.