Tamoxifen Citrate is the trade name for the drug tamoxifen citrate, it is a non-steroidal agent that demonstrates potent anti-estrogenic properties. The drug is technically an estrogen agonist/antagonist, which competitively binds to estrogen receptors in various target tissues. With the tamoxifen molecule bound to this receptor, estrogen is blocked from exerting any action, and an anti-estrogenic effect is achieved.
Tamoxifen Citrate is an estrogen agonist in the liver, capable of activating the estrogen receptor and mimicking the actions of this sex hormone in this region of the body. As such it can have a markedly positive impact on HDL (good) cholesterol values, as does estrogen.
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 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.
The claim that Nolvadex reduces gains should not be taken too seriously. The fact is that any number of bodybuilders have made excellent gains while using Nolvadex.
The belief that it reduces gains seems to stem from the fact that the scientific literature reports a slight reduction (individuals using anabolic steroids were not studied though) from use of Nolvadex.