The
macrolides are generally considered to be inhibitors of CYP3A4; however, it should be noted that they vary in the strength of their effect.
Macrolides that are more potent inhibitors of CYP3A4 are likely to have greater effects on substrates of this isoenzyme, and therefore their use seems more likely to be associated with greater
clinical consequences. Clarithromycin,
erythromycin and
telithromycin have the greatest effects, josamycin, midecamycin and roxithromycin have moderate effects, while
azithromycin,
dirithromycin and spiramycin only inhibit CYP3A4 to a small or clinically irrelevant extent. Note that
clarithromycin is often predicted to have a more potent effect on CYP3A4 than
erythromycin, but in many
clinical studies this has not been shown to be the case, for example, see under phosphodiesterase type-5 inhibitors.