Tamoxifen metabolism is altered by simultaneous administration of medroxyprogesterone acetate in breast cancer patients.

We have measured the levels of tamoxifen and three of its metabolites in the blood of patients receiving tamoxifen alone or combination therapy with tamoxifen and medroxyprogesterone acetate. Our results indicate that addition of the progestogen significantly alters the metabolism of tamoxifen over a six-month period. We suggest that the interaction between these drugs may involve additional sites (probably hepatic) besides the desired target tumour.

RCT Entities:   Population Interventions Outcomes