Levothyroxine Rifampicin

A significantly raised concentration of TSH during therapy with rifampicin has been reported in a man taking levothyroxine TSH concentrations returned to baseline 9 days after withdrawal of rifampicin (1009). 

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

Induction of cytochrome P450 may be the explanation for a modest increase in the clearance of levothyroxine (10-15%) which may necessitate an increase in dosage. In two cases, rifampicin led to significant increases in TSH concentrations in patients being treated for hypothyroidism (30). 

A woman with Turner s syndrome, who had undergone a total thyroidectomy and who was being treated with levothyroxine 100 micrograms daily, had a marked fall in serum levothyroxine levels and free levothyroxine index with a dramatic rise in TSH levels when given rifampicin. However, no symptoms of clinical hypothyroidism developed, and the drop in serum levothyroxine occurred prior to starting rifampicin, which may reflect the clinicd picture of an acute infection. Another case describes a fall in TSH levels when rifampicin was discontinued. ... 

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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