Hormonal Contraceptives Flashcards
Hormonal Contraceptives (HCs)
General
Contain synthetic analogs of the reproductive hormones (estrogen and/or progesterone)
Act synergistically to produce anti-ovulatory effects
Suppression of GnRH
Affect the endometrial lining (↓ bleeding and pain associated with menstruation)
Available formulations:
Oral contraceptive pills (combined and progestin-only)
Transdermal patches
Vaginal rings
Progestin injections
Subdermal implants
Intrauterine devices
Choice of Contraception
The choice of contraceptive method is individualized and often is dictated by a variety of factors:
Ease of access and use (dosing regimen, required procedures)
Affordability
Efficacy rate
Reversibility or permanence
Prevention of STIs
Adverse effects
Medical contraindications
Ethical and moral beliefs
Chemistry review
Ethinyl estradiol (EE)
Both estrogens and progestins are steroidhormones, making them fat-soluble and highly protein-bound
Ethinyl estradiol (EE):
Very similar in structure to natural estradiol
Addition of an ethynyl group (C2H) makes it significantly more stable than estradiol
↑bioavailability as compared with estradiol when taken orally
~50% (natural estradiolis only ~5%)
Only estrogen used in hormonal contraception (variable doses)
chemsirty review
progestins
Progestins:
Similar in structure to progesterone
Addition of a triple bond in most cases makes the molecules more stable
Androgenic effects:
Most are derived from testosterone → have stronger androgenic effects than natural progesterone
Less androgenic: norgestimate, etonogestrel, and desogestrel
Antiandrogenic activity: drospirenone (spironolactone analog)
Multiple different progestins are used in HCs → different properties of the progestins are responsible for different side-effect profiles of various HCs
Normal Physiology of theMenstrual Cycle
HPO axis
Understanding hormonal regulation of ovulation and themenstrual cycleis key to understanding the mechanisms of hormonal contraceptives
HPO axis:
Hypothalamussecretes gonadotropin-releasing hormone (GnRH)
Pituitary secretes:
Follicle-stimulating hormone (FSH)
Luteinizing hormone (LH)
Ovary secretes:
Estrogen
Progesterone
Menstrual cycle regulation is primarily by the hypothalamic-pituitary-ovarian (HPO) axis
Normal Physiology of theMenstrual Cycle
Follicular/Proliferative phase
Follicular/Proliferative phase:
GnRH pulse stimulates the release of FSH
FSH stimulates follicular development within theovaries
Developing follicles produce estrogen (estradiol)
Estrogen:
Stimulates endometrial proliferation
Inhibits FSH secretion (feedback inhibition)
Ovulation:
Triggered by a midcycle surge of LH
Normal Physiology of theMenstrual Cycle
Luteal/Secretory phase
Luteal/Secretory phase:
The ovulated follicle is now called the corpus luteum
The corpus luteum produces progesterone and a moderate amount of estrogen
Progesterone:
Stabilizes endometrium
Causes endometrium to mature into secretory endometrium, capable of sustaining apregnancy
Progesterone = “progestational hormone” → produced only after ovulation, when gestation is possible
If pregnant: corpus luteum continues producing progesterone until theplacentacan take over
If not pregnant: corpus luteum involutes → estradiol and progesterone levels fall
Normal Physiology of theMenstrual Cycle
menstrual phase
Menstrual phase:
Loss of stabilizing hormones (particularly progesterone) triggers breakdown of the endometrium → menses
Key point: Progesterone withdrawal triggers bleeding
Mechanism of Action of Hormonal Contraceptives
Estrogen
Both estrogens and progestins cause an antiovulatory effect
Used together, this effect is SYNERGISTIC
Estrogen component:
Inhibits FSH release → prevents the selection and maturation of the dominant follicle = No ovulation
Stimulates endometrial proliferation if given without progestin (↑ a patient’s risk for certain cancers) → ethinyl estradiol is NOT given alone
Mechanism of Action of Hormonal Contraceptives
Progestin
Progestin component:
Inhibits LH surge that is necessary for ovulation by decreasing the pulse frequency of the GnRH
Effects on the endometrium:
Natural progesterone is required to make the endometrium healthy forpregnancy
Androgenic nature of synthetic progestins thins the endometrial lining, making it unsuitable for implantation
All hormonal contraceptives are “progestin-dominant” → overall endometrial effect of hormonal contraceptives is endometrial atrophy
↑ Cervical mucus viscosity → inhibits sperm transport into the uterus
↓ Cilia motility in the fallopian tube
Classification of Hormonal Contraceptives
Grouped by the length of their action and route of administration
Short-acting contraceptives
Includes pills, patches, rings, and injections
Long-acting reversible contraceptives (LARCs)
Emergency contraception
Short-acting contraceptives
Combined Oral Contraceptive Pills (COCPs)
We
Classified by the number of “phases”:
Monophasic: Each pill contains fixed amounts of ethinyl estradiol and progestin
Biphasic: Variable amounts of ethinyl estradiol and a form progestin
Triphasic: Variable amounts of ethinyl estradiol and a form progestin
Low-dose ethinyl estradiol (10-35 mcg) preferred to high-dose (50 mcg)
Daily administration
Initiation on the first day of the menstrual cycle or first Sunday after the onset of the cycle
NOTE: Patients using the first Sunday start are not protected from pregnancy in the first 7 days and an additional form of birth control will be needed
Pregnancy rate
0.3% with perfect use
8% with typical use
Combined Oral Contraceptive Pills (COCPs)
Non-contraceptive benefits:
More regular, lighter, shorter menses
Improvement of dysmenorrhea symptoms (cramping)
Decreased risk of ovarian, endometrial, and colon cancers
Improvement of acne and unwanted hair growth
Functional ovarian cysts are less likely
Lower frequency of uterine myomas with taking COCPs > 4 years
Reduce the frequency of migraines associated with menstruation (NOT for use in patients with migraines with aura)
Transdermal patch
Small, square adhesive patch worn on the skin
Buttocks, chest (not the breasts), upper back or arm, or abdomen
Releases ethinyl estradiol and norelgestromin or levonorgestrel daily which is absorbed through the skin
Hormone blood levels are more constant with the patch than with OCs
Weekly administration
1 patch applied per week for 3 weeks in a row
Rotate application sites
No patch applied for 7 days…menses occurs
Less effective in women > 90 kg
Vaginal ring
Flexible, transparent, plastic ring that is placed in the upper vagina
Releases ethinyl estradiol and a progestin (etonorgestrel = NuvaRing; segesterone = Annovera) that is absorbed through the vaginal tissues
Ring types
Month-long (NuvaRing)
1 ring inserted for 3 weeks/21 days; removed for 7 days…menses occurs
Replaced each month
Year-long (Annovera)
1 ring inserted for 3 weeks/21 days; removed for 7 days…menses occurs
Replaced once a year