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
have the greatest effects, josamycin, midecamycin and roxithromycin have moderate effects, while azithromycin
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.