Menstrual cycle between 45 and 55 years of age. Bleeding usually lasts around 2 to 7 days. The menstrual cycle is governed by hormonal changes. These changes can be altered by using hormonal birth control to prevent pregnancy. Each cycle can be divided into three phases based on events in the ovary (ovarian cycle) or in the uterus (uterine cycle). The ovarian cycle consists of the follicular phase, ovulation, and luteal phase whereas the uterine cycle is divided into menstruation, proliferative phase, and secretory phase. Stimulated by gradually increasing amounts of estrogen in the follicular phase, discharges of blood (menses) flow stop,
Pharmacokinetics of progesterone and has been found to result in higher serum peak progesterone levels relative to intramuscular oil formulations. In addition, subcutaneous injection of progesterone is considered to be easier, safer (less risk of injection site reactions), and less painful relative to intramuscular injection. The elimination half-life of this formulation is 13 to 18 hours, compared to 20 to 28 hours for intramuscular injection in oil. Progesterone has a very short elimination half-life of about 3 to 90 minutes when given by intravenous injection. A one-year progesterone intrauterine device (IUD) for hormonal birth control was previously available in the United States and