Contraception and Clinical Pharmacy

Study Notes

Introduction to Contraception

Contraception is the prevention of pregnancy by inhibiting sperm from reaching a mature ovum or by preventing a fertilized ovum from implanting in the endometrium.
Hormonal contraception is used by cis women and transgender individuals.

Menstrual Cycle Pathophysiology

The median menstrual cycle length is 28 days, ranging from 21-40 days.
The cycle consists of the follicular phase, ovulation, and the luteal phase.
The hypothalamus secretes gonadotropin releasing hormone, which stimulates the anterior pituitary to secrete follicle stimulating hormone (FSH) and luteinizing hormone (LH).
In the follicular phase, FSH levels increase, causing recruitment of a small group of follicles, and one of these becomes the dominant follicle.
The dominant follicle develops increasing amounts of estradiol and inhibin, providing negative feedback on the secretion of gonadotropin releasing hormone and FSH.
The dominant follicle continues to grow and synthesizes estradiol, progesterone, and androgen.
Estradiol stops the menstrual flow from the previous cycle, thickens the endometrial lining, and produces thin, watery cervical mucus.
The pituitary releases a midcycle LH surge that stimulates the final stages of follicular maturation and ovulation.
Ovulation occurs 24-36 hours after the estradiol peak and 10-16 hours after the LH peak.
The LH surge is the most clinically useful predictor of approaching ovulation.
Conception is most successful when intercourse takes place from 2 days before ovulation to the day of ovulation.
After ovulation, the remaining luteinized follicles become the corpus luteum, which synthesizes androgen, estrogen, and progesterone.
If pregnancy occurs, human chorionic gonadotropin prevents regression of the corpus luteum and stimulates continued production of estrogen and progesterone.
If pregnancy does not occur, the corpus luteum degenerates, progesterone declines, and menstruation occurs.

Treatment of Contraception

The goal of treatment is the prevention of pregnancy from sexual intercourse.

Non-Pharmacologic Therapy

The internal condom (female condom) covers the labia and cervix, with a higher pregnancy rate than external condoms, but protects against many viruses, including HIV.
Do not use external and internal condoms together.
Spermicides contain nonoxynol-9, a surfactant that destroys sperm cell walls and blocks entry into the cervical os.
Spermicides offer no protection against STIs, and when used more than twice daily, nonoxynol-9 may increase HIV transmission.
Phexxi is a prescription nonoxynol-9 free spermicide that reduces vaginal pH to reduce sperm motility, but carries a risk of cystitis.
The vaginal contraceptive sponge is available over the counter and contains nonoxynol-9, providing protection for 24 hours.

Hormonal Contraceptives

With perfect use, CHC efficacy is more than 99%, but with typical use, up to 7% of individuals will have unintended pregnancy.
Monophasic CHCs contain a constant amount of estrogen and progestin for 21 days.
Biphasic and triphasic pills contain variable amounts of estrogen and progestin for 21 days.
Extended cycle pills and continuous combination regimens may reduce adverse effects and are more convenient.
The progestin-only “minipills” are less effective than CHCs and are associated with irregular and unpredictable menstrual bleeding.
The first day start method, Sunday start method, and quick start method are different ways to start hormonal contraception.

Transdermal Contraceptives

Two combination contraceptives are available as a transdermal patch: Xulane and Twirla.
Xulane delivers 35 mcgEE and 150 mcg norgestimate daily, while Twirla provides 120 mcg of levonorgestrel and 30 mcg of EE daily.
These patches are effective as CHCs in individuals weighing less than 90 kg (198 lb) or having a BMI less than 30 kg/m2, with failure rates between 3% and 7%.
Apply the patch to the abdomen, buttocks, upper torso, or upper arm at the beginning of the menstrual cycle and replace every week for 3 weeks.

Vaginal Rings

There are two vaginal rings available: NuvaRing and Annovera.
NuvaRing releases ∼15 mcg/day of EE and 120 mcg/day of etonogestrel, while Annovera releases 13 mcg of EE and 150 mcg of segesterone acetate.
On first use, the ring should be inserted on or prior to the fifth day of the cycle, remain in place for 3 weeks, and then be removed.