Quinestrol is a prodrug of ethinylestradiol (EE), with no estrogenic activity of its own.[1][8][9] It is taken orally and has prolonged activity following a single dose,[8][9] with a very long biological half-life of more than 120 hours (5 days) due to enhanced lipophilicity and storage in fat.[3][1] Because of its much longer half-life, quinestrol is two to three times as potent as EE.[3] Also because of its long half-life, quinestrol can be taken once a week or once a month.[3][5][6][7][8]