Oral Contraceptives Flashcards
What are the characteristics of Oral Contraceptives?
Usually contain a mixture of estrogen & progestin which act by inhibiting ovulation
● Estrogen is considered the major ovulation inhibitor
● Relatively high level of estrogen inhibits release of FSH / LH from pituitary
so that the follicle does not develop
● Progestins mainly decreases the frequency of pulses of GnRH release from the
hypothalamus. Because the proper frequency of LH pulses is essential for ovulation, this effect of progestins likely plays a role in the contraceptive action of these agents
● C-19s produce thick, hostile environment for sperm migration (major MOA)
● Inclusion in OC’s ensure a “physiological” withdrawal bleeding that resembles normal menstruation when pills are stopped
What is the MOA of Oral Contraceptives?
o Continual fairly high levels of estrogen & progestin in blood prevent GnRH, LH, & FSH
release – so ovulation does not occur
o Changes in milieu of mucosal lining of cervix & uterine endometrium
o Changes the motility & secretion pattern within fallopian tube
What is the Therapeutic regimen for Oral Contraceptives?
Usually use 35mcg ethinyl estradiol
What is the Therapy regimen for Combined Oral Contraceptives?
● Estrogen & progestin on days 5-25 (followed by placebo pills)
● Theoretical effectiveness = 99.9%
● Use effectiveness = 97-98%
What is the Therapy regimen for Sequential Oral Contraceptives?
● Estrogen alone for 15 days, then estrogen & progesterone for 5 days
● Discontinued – risk of endometrial cancer (due to unopposed estrogen)
What is Continuous low dose progestin (“ minipill ”) Oral Contraceptives?
● Progestin only
● Not reliable as an inhibitor of ovulation (block in only 75-80% of cycles)
● Increased incidence of unpredictable spotting & breakthrough bleeding
● Use effectiveness = 96-97.5% (less than combo therapy)
● Advantage = serious side effects of combo therapy (ex: clotting,
thrombosis) are due to estrogen component and are hence eliminated
What is the Therapy regimen for Phasic Oral Contraceptives?
● Varying doses of estrogen & progestin components during the month to more closely approximate a normal menstrual cycle
What is the Therapy regimen for Depot Therapy Contraceptives?
● Injections of long-lasting estrogens and/or progestins
● Medroxyprogesteron acetate (Depo-Provera®) – give IM 1x / 3 months
What is the Therapy regimen for Patch Contraceptives?
● Ortho-Evra – apply patch once a week
What is the Therapy regimen for Subdermal Implants Contraceptives?
● Capsules of etonorgestrel under skin for slow release (work up to 3 years)
What is the MOA, side effects, and therapy regimen for Post-coital Contraceptives?
● MOA: prevent implantation of the fertilized ovum and/or alter motility of the fertilized ovum through Fallopian tube
● Severe nausea / vomiting = side effect of high estrogen content pills
● Formerly used high doses of estrogens
● Plan B® = L-norgestrel 0.75mg twice daily for 1 day (progestin only)
What is Mifepristone (RU486)?
● Progesterone antagonist that inhibits the actions of progesterone on the uterus during luteal phase; can detach embryo from uterine wall leading to abortion → administered with misoprostol (a prostaglandin)to expel embryo
