Rifampicin Contraceptives, hormonal

Hormonal contraceptives Rifampicin Therapeutic failure of contraceptive... 

Levonorgestrel is metabolised to inactive substances before it is conjugated, and does not therefore undergo enterohepatic recycling of the active moiety. There is no reason to expect that its efficacy as an emergency contraceptive would be affected by antibacterials that alter gut flora and do not induce liver enzymes. No special precautions are necessary with these antibacterials. However, rifampicin and rifabutin are likely to reduce the efficacy of most forms of hormonal contraceptives, as they induce the metabolism of oestrogens and progestagens, see Hormonal contraceptives + Rifamycins , p. 1001. 

The efficacy of both the progestogen-only and combined emergency hormonal contraceptive is likely to be reduced by enzyme inducers such as rifampicin and some antiepileptics. 

Hormonal contraceptives are less reliable during treatment with rifampicin. Breakthrough bleeding and spotting commonly occur, and pregnancy may not be prevented. Rifabutin also reduces the reliability of hormonal contraceptives, although it interacts to a lesser extent, and no contraceptive failures appear to have been reported. 

The FFPRHC has issued guidance on the use of liver enzyme inducers, such as rifampicin and rifabutin, with all forms of hormonal contraceptives, including the emergency hormonal contraceptive, and these are given in detail elsewhere, see Hormonal contraceptives + Antiepileptics Barhiturates or Phenytoin , p.985. 

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