Question

A provider considers prescribing tamoxifen for a woman with breast cancer. Upon reviewing results of genetic testing, the prescriber notes that the patient has variations in the CYP2D6 allele resulting in a deficiency of the CYP2D6 isoenzymes. What action will this deficiency warrant in the prescribing of tamoxifen, a CYP2D6 substrate?

Group of answer choices

The tamoxifen will not be prescribed.

The tamoxifen will be ordered but in lower than normal dosage.

The patient’s serum tamoxifen level will be routinely monitored.

The individual doses of tamoxifen will be increased.

Answer 1

The answer is -------- The tamoxifen will not be prescribed.

Explanation :

Tamoxifen is converted into endoxifen, which is the most potent metabolite in presence of an enzyme CYP2D6 . This helps in treating hormonal cancers such as breast cancer and also prevents the relapse of breast cancer after treated. However, if the person is deficient in CYP2D6 enzyme, the active metabolite is not formed and hence the treatment is ineffective and therefore substitute for tamoxifen is used .

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