Clomid (Clomiphene Citrate) belongs to a category and class of drugs known as selective Estrogen receptor modulators (SERMs). Selective Estrogen receptor modulators belong to an even broader class of drugs known as anti-estrogens. The other subcategory of drug under the anti-estrogens category is known as aromatase inhibitors (AIs), such as Aromasin (Exemestane) and Arimidex (Anastrozole). AIs and SERMs make up anti-estrogens. Aromatase inhibitors differ greatly from SERMs in their action and how they deal with the issues of estrogen control. The misunderstanding that SERMs, such as Nolvadex and Clomid, serve to lower estrogen levels must first be addressed before delving into any further details.