Objective: To describe the current drug interaction profiles for the commonly used macrolides in the US and Europe, and to comment on the clinical impact of these interactions.
Data sources: A MEDLINE search (1975-1998) was performed to identify all pertinent studies, review articles, and case reports. When appropriate information was not available in the literature, data were obtained from the product manufacturers.
Study selection: All available data were reviewed to provide an unbiased account of possible drug interactions.
Data extraction: Data for some of the interactions were not available from the literature, but were available from abstracts or company-supplied materials. Although the data were not always explicit, the best attempt was made to deliver pertinent information that clinical practitioners would need to formulate practice opinions. When more in-depth information was supplied in the form of a review or study report, a thorough explanation of pertinent methodology was supplied.
Data synthesis: Several clinically significant drug interactions have been identified since the approval of erythromycin. These interactions usually were related to the inhibition of the cytochrome P450 enzyme systems, which are responsible for the metabolism of many drugs. The decreased metabolism by the macrolides has in some instances resulted in potentially severe adverse events. The development and marketing of newer macrolides are hoped to improve the drug interaction profile associated with this class. However, this has produced variable success. Some of the newer macrolides demonstrated an interaction profile similar to that of erythromycin; others have improved profiles. The most success in avoiding drug interactions related to the inhibition of cytochrome P450 has been through the development of the azalide subclass, of which azithromycin is the first and only to be marketed. Azithromycin has not been demonstrated to inhibit the cytochrome P450 system in studies using a human liver microsome model, and to date has produced none of the classic drug interactions characteristic of the macrolides.
Conclusions: Most of the available data regarding macrolide drug interactions are from studies in healthy volunteers and case reports. These data suggest that clarithromycin appears to have an interaction profile similar to that of erythromycin. Given this similarity, it is important to consider the interaction profile of clarithromycin when using erythromycin. This is especially necessary as funds for further studies of a medication available in generic form (e.g., erythromycin) are limited. Azithromycin has produced few clinically significant interactions with any agent cleared through the cytochrome P450 enzyme system. Although the available data are promising, the final test should come from studies conducted in patients who are taking potentially interacting compounds on a chronic basis.