Abstract
IntroductionTibolone is a synthetic steroid, used with increasing frequency to treat symptoms of menopause, including patients with solid-organ transplants who are taking concurrent immune suppression. To the best of our knowledge, there are no reported drug interactions between tibolone and tacrolimus, one of the principal immune suppressants used in kidney transplantation.Case presentationWe report the case of a 49-year-old Caucasian woman who had received a kidney transplant and who developed acute kidney injury secondary to tacrolimus toxicity 10 days after starting tibolone therapy. No alternative causes were found. Tibolone is known to be a weak competitive inhibitor of CYP3A4, which is involved in tacrolimus metabolism.ConclusionsDespite a careful evaluation, no alternative reason was found for the acute kidney injury, and her kidney function returned to the previous baseline within several days of cessation of the medication, and with no other specific treatment. Using the Drug Interaction Probability Scale we conclude that she experienced a probable drug interaction. We believe that transplant clinicians should utilise frequent therapeutic drug monitoring of tacrolimus in patients starting or stopping tibolone therapy.
Highlights
Tibolone is a synthetic steroid, used with increasing frequency to treat symptoms of menopause, including patients with solid-organ transplants who are taking concurrent immune suppression
Despite a careful evaluation, no alternative reason was found for the acute kidney injury, and her kidney function returned to the previous baseline within several days of cessation of the medication, and with no other specific treatment
We believe that transplant clinicians should utilise frequent therapeutic drug monitoring of tacrolimus in patients starting or stopping tibolone therapy
Summary
Given the polymorphisms in the cytochrome P450 metabolic pathway and the potential for a wide variation in the metabolism of these two drugs, there is a strong likelihood that other patients may experience a similar interaction. Given pharmacogenetic variability, not all patients would be expected to be affected. Primary care physicians may not seek the advice of transplant specialists for treatment not directly related to the transplant, and given that there are no reports in the literature, would not expect a complication such as this. We believe that all clinicians (transplant and primary care) should be aware of this probable drug interaction and should ensure monitoring of tacrolimus concentration within three days of commencement of tibolone. Doi:10.1186/1752-1947-4-276 Cite this article as: Clark et al.: Probable tacrolimus toxicity from tibolone co-administration in a woman: a case report. Consent Written informed consent was obtained from the patient for publication of this case report and any accompanying images. CH reviewed our case report and provided her data. All authors read and approved the final manuscript
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