Activella is a popular drug that is made from two important ingredients: estradiol and norethindrone. Estradiol is a well known female sex hormone (an estrogen form) that is known to be involved in the maintenance and in the development of the female reproductive system. Norethindrone is one of progesterone’s forms. Progesterone is another important female hormone that plays a big part in the regulation of menstruation and ovulation.