Chlormadinone acetate

Chlormadinone acetate is a progesterone derivative first synthesized in 1961. In the US, chlormadinone acetate was formerly marketed as a component of the combination drug products Estalor-21 and C-Quens. However, the use of these drugs was associated with the development of mammary tumors in dogs. In 1972, the FDA withdrew its approval for the use of chlormadinone acetate in all products. Chlormadinone acetate continues to be used in other countries due to its high contraceptive efficacy and tolerability.