Hormonal Rifampicin

THYROID HORMONES RIFAMPICIN 1 levothyroxine levels Induction of metabolism Monitor TFTs regularly and consider t dose of levothyroxine... 

Hormonal contraceptives Rifampicin Therapeutic failure of contraceptive... 

Hypothyroidism developed within 2 weeks of rifampicin therapy in these patients and resolved when it was withdrawn. Rifampicin increases thyroxine clearance, possibly by enhancing hepatic thyroxine metabolism and the biliary excretion of iodothyronine conjugates. In healthy volunteers rifampicin reduces circulating thyroid hormone concentrations without affecting thyrotropin, suggesting that rifampicin directly reduces thyroid hormone concentrations. 

The drug interactions with rifampicin and ciprofloxacin would also need to be taken into account if hormonal methods were used [19, 36]. 

Owen, A., Goldring, C., Morgan, P., Park, B. K., and Pirmohamed, M. (2006) Induction of P-glycoprotein in lymphocytes by carbamazepine and rifampicin the role of nuclear hormone response elements. Br. J. Clin. Pharmacol. 62, 237-242. 

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. 

Two case reports surest that rifampicin might possibly reduce the effects of thyroid hormones. 

There seem to be no reports of adverse effects in other patients given both drugs and the evidence for this interaction is by no means conclusive. Although rifampicin can affect thyroid hormones, it appears that healthy individuals can compensate for this. Since hypothyroid patients may not be able to compensate in the same way, bear this interaction in mind if rifampicin is given to a patient taking levothyroxine. 

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