Nolvadex (Tamoxifen Citrate) is very comparable to Clomid, behaves in the same manner in all tissues, and is a mixed estrogen agonist/antagonist of the same type as Clomid. The two molecules are also very similar in structure.

It is not correct that Nolvadex (Tamoxifen Citrate) reduces levels of estrogen: rather, it blocks estrogen from estrogen receptors and, in those tissues where it is an antagonist, causes the receptor to do nothing.