Progesterone implant

Suarez AA, Brunt EM, Di Bisceglie AM. A 35-year-old woman with progesterone implant contraception and multiple hver masses. Semin Liver Dis 2001 21(3) 453-9. 

Croxatta, H.B., et al. 1982. Fertility regulation in nursing women. II. Comparative performance of progesterone implants versus placebo and copper T. Am J Obstet Gynecol 144 201. 

Progestins (progesterone) Implantation of fertilized eggs and maintenance of pregnancy... 

As under most circumstances progesterone action will hold primacy over estrogenic effects, the cervical mucus, endometrium, and probably the fallopian tubes reflect progestational stimulation. The cervical mucus becomes thick and viscous and thus impervious to spermatozoa. The endometrium is in a state that is not receptive for implantation of a fertilized egg. Probably, the progestational impact on the secretory activity and peristalsis in the fallopian tubes also assists the general contraceptive effect. It is difficult, however, to assess the relative contribution of the various effects to the... 

Ema M, Harazono A, Hirose A, Kamata E (2003) Protective effects of progesterone on implantation failure induced by dibutyitin dichloride in rats. Toxicology Letters, 143(2) 233-238. 

The earliest reports of controlled release steroids were those of Jackanicz (63), Yolles (64), Anderson (65), and Wise (66). Most of those early studies were based on poly[ (L+)-lactic acid). Implants and granular particles were fabricated with progesterone, norgestrel, and norethisterone. In vivo urinary excretion studies were conducted on [I Cjprogesterone beads (64). The reported results were somewhat questionable as only 20% of the original implanted drug could be accounted for. 

The release of steroids such as progesterone from films of PCL and its copolymers with lactic acid has been shown to be rapid (Fig. 10) and to exhibit the expected (time)l/2 kinetics when corrected for the contribution of an aqueous boundary layer (68). The kinetics were consistent with phase separation of the steroid in the polymer and a Fickian diffusion process. The release rates, reflecting the permeability coefficient, depended on the method of film preparation and were greater with compression molded films than solution cast films. In vivo release rates from films implanted in rabbits was very rapid, being essentially identical to the rate of excretion of a bolus injection of progesterone, i. e., the rate of excretion rather than the rate of release from the polymer was rate determining. 

Ethylene vinyl acetate has also found major applications in drug delivery. These copolymers used in drug release normally contain 30-50 wt% of vinyl acetate. They have been commercialized by the Alza Corporation for the delivery of pilocarpine over a one-week period (Ocusert) and the delivery of progesterone for over one year in the form of an intrauterine device (Progestasert). Ethylene vinyl acetate has also been evaluated for the release of macromolecules such as proteins. The release of proteins form these polymers is by a porous diffusion and the pore structure can be used to control the rate of release (3). Similar nonbiodegradable polymers such as the polyurethanes, polyethylenes, polytetrafluoroethylene and poly(methyl methacrylate) have also been used to deliver a variety of different pharmaceutical agents usually as implants or removal devices. 

Progestins, of which progesterone is a prime example, induce endometrial maturation following ovulation, setting the stage for implantation of a fertilized ovum and pregnancy ... 

Oestradiol and progesterone regulate the structural and functional changes in oviducts, uterus, cervix and vagina that occur during the menstrual cycle. They provide conditions in the oviduct for the upward motility of sperm, and the downward movement of ova, and also conditions favourable for fertilisation in the oviduct and implantation in the uterus. Another effect is to stimulate vaginal secretions. 

If fertilisation does not occur, the corpus luteum regresses and the levels of oestrogen and progesterone fall. However, if fertilisation does occur, the corpus luteum is maintained. Regression of the corpus luteum is prevented by the implanting blastocyst which secretes a hormone, human chorionic gonadotrophin (hCG). This occurs about a week after fertilisation. The structure of this hormone is similar to that of LH and it takes on the role of LH in maintenance of the corpus luteum. To do this, it binds to the LH receptor... 

An anti-progesterone (mifepristone, RU 486) pill is used to inhibit ovulation and implantation. 

The hormones probably decrease the magnitude of the midcycle LH surge and, therefore, effectively prevent ovulation. The anti-progesterone drug delays endometrial maturation so that implantation does not take place. It may be effective up to five days after intercourse, since implantation occurs seven days after ovulation. 

LH secretion which induces rupture of the follicle and release of the mature egg into the fallopian tube. In the ovary a corpus luteum forms, which secretes progesterone (maximal at about day 21) to prepare the endometrium for implantation of an early embryo. If pregnancy does not occur, the corpus luteum involutes, progesterone levels fall, and the thickened endometrium is shed giving rise to menstrual bleeding, which is defined as starting on day 1 of the next cycle. 

When implantation of the ovum does not occur, estrogen and progesterone levels fall and menstrual... 

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