Tamoxifen is a drug used to prevent recurrence of certain types of breast cancers that require estrogen to grow. tamoxifen binds to the active site of the estrogen receptor protein, preventing estrogen from binding to the enzyme. once tamoxifen binds to the protein, the protein is permanently deactivated. which of the following descriptions best fits tamoxifen? a. tamoxifen is a reversible, noncompetitive inhibitor. b. tamoxifen is an irreversible, noncompetitive inhibitor. tamoxifen is an irreversible, competitive inhibitor. d. tamoxifen is a reversible, competitive inhibitor. e. tamoxifen is not an inhibitor.