Erythromycin Hormonal contraceptives

When acne is severe it may require medidnes that have to be taken by mouth and these may be stronger antibiotics combined with hormone therapy. Tetracyclines and erythromycin are typically used and they have to be taken for many weeks, but there are signs that bacteria are becoming resistant to these antibiotics and if there is no improvement in the acne within three months then this type of treatment has to be discontinued, or a much stronger antibiotic tried. Hormone therapy is available for young women with severe acne and this can block the sebum-stimulating effect of natural hormones - as well as having a contraceptive effect. 

The macrolides clarithromycin, dirithromycin, roxithromycin and telithromycin appear unlikely to cause combined hormonal contraceptive failure. Erythromycin is also not considered to cause failure of combined hormonal contraceptives, but isolated anecdotal cases have been reported. An isolated case has also been reported with spiramycin. 

The macrolides such as erythromycin might possibly be expected to suppress the bacteria responsible for the enterohepatic recycling of ethinylestradiol, but good evidence that this is clinically important is scant (see Hormonal contraceptives + Antibacterials Penicillins , p.981). Erythromycin, and to a lesser extent the other macrolides discussed here, also inhibit the cytochrome P450 isoenzyme CYP3A4, which is responsible for the metabolism of the contraceptive steroids. Therefore they might be expected to increase rather than reduce contraceptive efficacy. This would be expected to offset any possible reduced enterohepatic recycling. 

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