LM 16.2: Pharmacology of Contraception Flashcards
what does progesterone do to the endometrium?
it stimulates the endometrial glands to dilate, fill with glycogen, and become secretory while stromal vascularity increases
how long does the corpus luteum persist?
if the oocyte is fertilized, then the hCG produced from the new embryo will rescue the corpus luteum and allow it to continue progesterone production until the 9th or 10th gestational week –> then, the fetal placenta will take over progesterone production throughout pregnancy
if progesterone levels are not maintained by the rescued corpus luteum, estradiol and progesterone levels decrease late in the luteal/secretory phase, the stroma becomes edematous, and the endometrium and its blood vessels necrose, leading to bleeding and menstrual flow
how do combined hormonal contraceptives work?
the interplay of the steroid hormones, estradiol and progesterone, with the gonadotrophs, LH and FSH, is the principle mechanism by which combined hormonal contraceptives work
the constant level of steroid hormones allow for continuous negative feedback on gonadotroph production from the pituitary – so with OCPs, stable levels of estradiol and progestin result in negative feedback on GnRH and then during the placebo week when estradiol and progesterone levels drop, you get menstration!
this inhibition provided by hormonal contraceptives prevents the rise in FSH that is necessary to initiate follicle development and selection of a dominant follicle – this inhibition also prevents the LH surge that is necessary to trigger ovulation!
how does ethinyl estradiol function as hormonal contraception?
it suppresses FSH continuously, inhibiting dominant follicle growth
it also potentiates progesterone receptors which stabilizes the endometrium
ethinyl estradiol has greater bioavailability than estradiol and is metabolized through the liver
what are side effects of ethinyl estradiol?
MINOR
1. breast tenderness
- nausea
- HA
- fluid retention
MAJOR
dose-related side effects of increasing clotting factors and thereby risk of thrombosis (arterial and venous) and cardiovascular events (MI/stroke)
how does ethinyl estradiol effect acne?
higher doses result in increased steroid hormone binding globulin (SHBG) therefore decreased circulating androgens and subsequent decreased androgenic side effects, like acne
how do progestins function as hormonal contraception?
it suppresses LH surge and prevents ovulation
it also causes endometrial decidualization and thinning, thickens cervical mucus, may decrease tubal peristalsis
what are the side effects of progestins?
- menstrual irregularities
- hair changes
- loss of bone mineral density
- mood changes
- increased appetite
- weight gain
also, based on which progestin derivative you’re using, it might have androgenic, estrogenic, glucocorticoid, anti-mineralocorticoid or anti-androgenic properties
how do progestins effect bone mineral density?
loss of bone mineral density
progestins significantly inhibits estrogen production and therefore limits the effect of estrogen on inhibiting bone resorption by osteoclasts
this effect is however reversible with discontinuation of the long acting progestin
what are the progesterone derivatives?
- progesterone
- hydroxyprogesterone caproate
- medroxyprogesterone acetate
- 19-nortestosterone
- norethindrone
- norethynodrel
- norgestrel
- desogestrel
- norgestimate
which drugs are first generation progesterones?
- megestrol acetate
- medroxyprogesterone acetate (MPA)
pregnanes have an extra methyl group at C6, which decreases first-pass hepatic metabolism and thus makes these formulations orally available
which drugs are second generation estranes?
- norethindrone
- norethindrone acetate
- ethynodiol
- lynestrenol
estranes have lost the methyl group at C19, which decreases androgenic activity
which drugs are third generation gonanes?
- norgestrel
- levonorgestrel
- desogestrel
- norgestimate
- gestodene
- dienogest
gonanes have replaced the methyl group at C13 with an ethyl group, which again decreases androgenic activity
what is drosperinone?
a synthetic progestin that is an analog to spironolactone and therefore has anti-mineralocorticoid and anti-androgenic activity
what are the 3 mechanisms by which combined hormonal contraceptives provide contraception?
- progestin thickens cervical mucus, inhibiting sperm transit
- estradiol component negatively feeds back to inhibit FSH and subsequent development of dominant follicle
- progestin component causes decidualization of endometrium, creating an unfavorable environment for implantation
what are the contraindications to estrogen based contraceptives?
- increased risk of thrombosis so contraindicated in patients with HTN
- increased risk for MI with contraceptive use –> the highest risk is in those women who use combination OCPs and are over the age of 35, with hypertension
- tobacco use –> to consider removing this risk factor, one must have quit smoking for a minimum of 6 months
- abnormal liver function
- migraines with auras (related to risk of stroke)
- DM with vascular disease
- estrogen sensitive breast cancer
- pregnancy
- sever hypercholesterolemia/hypertriglyceridemia
it is important to screen a patient’s vital signs, tobacco use and personal and family history of known thrombogenic mutations, CVA, TIA, heart disease, hypertension, MI, vascular disease and VTE, prior to prescribing CHC
what is the usual dosage for estrogen CHC?
more standard doses are 30-35 mcg EE, with lower doses ranging from 20-25 mcg EE
what are the benefits to lowering estrogen dosage in CHC?
lowering doses of ethinyl estradiol includes minimizing:
- nausea
- breast tenderness
- fluid retention
- headaches
however higher doses result in increased steroid hormone binding globulin (SHBG) and therefore decreased circulating androgens with subsequent decreased androgenic side effects, like acne
what are the routes of delivery for ethinyl estradiol CHC?
- oral
- transdermal
- vaginal
how are oral CHC metabolized?
via the liver
so they’re avoided in those with significant hepatic disease
what are monphasic, biphasic vs. triphasic OCPs?
they have varying doses of ethinyl estradiol
they typically having lower doses in the beginning of the regimen, reducing estrogen-related side effects like nausea then increasing doses through the month, therefore increasing SHBG, decreasing free androgens and decreasing androgen-related effects (like acne)
what are extended regimen OCPs?
pills with active steroid hormones for 24 day with a 4 day pill free interval
extended regiments reduce the pill free interval to decrease breakthrough bleeding and better suppress ovarian activity
what are continuous regimen OCPs?
active steroid hormones for a consecutive 84 days followed by a 7 day pill free interval, resulting in better suppression of ovarian activity
what are the non-contraceptive uses of CHCs?
- abnormal uterine bleeding
- dysmenorrhea
- endometriosis
- PCOS
- hirsutism
- acne
- menstrual migraines
what are the beneficial effects of contraception?
- with 12 months of use, there is a 50% reduction in risk of endometrial cancer for up to 20 years
- with as little as 3-6 months use, there is a 40% reduction in ovarian cancer risk
what are the cons of contraception?
- OCPs may result in behaviors that lead to a 3-fold increase in cervical cancer in HPV positive individuals after 5 years of use
- current and recent use may increase rates of premenopausal breast cancer
when should you initiate CHCs?
they should typically be started immediately (“quick start” method), provided that there is reasonable certainty of negative pregnancy and with the advice to use backup contraception for the first week of use
how can you be reasonably certain that a woman is not pregnant?
- if a patient’s last menstrual period was within 5 days
- if there was no unprotected intercourse since the time of her last menstrual period with a negative pregnancy test
if patient has not had a LMP within 5 days and has had unprotected intercourse but has a negative pregnancy test, contraception may be initiated with the caveat that pregnancy is not ruled out but that contraception is unlikely to have deleterious effects on pregnancy