Contraception, Oral, Injections, & Implants

General Considerations

• Unintended pregnancies are a worldwide problem but disproportionately impact developing countries

• Studies estimate that 40% of the 213 million pregnancies that occurred in 2012 were unintended

• Globally, 50% ended in abortion, 13% ended in miscarriage, and 38% resulted in an unplanned birth

• Primary care providers need to educate their patients about the benefits of contraception and to provide them options that are appropriate and desirable

Medications

Oral contraceptives

• Combination pills

  • Have a theoretical failure rate of only 0.3% if taken absolutely on schedule but a typical use failure rate of 8%

  • Primary mode of action is suppression of ovulation

  • Pills can be started on the first day of the menstrual cycle, on the first Sunday after the onset of the cycle, or on any day of the cycle

    • If started on any day other than the first day of the cycle, a backup contraceptive method should be used

    • The combination pill is taken daily for 21 days, followed by 7 days of placebos or no medication, and this schedule is continued for each cycle

    • If an active pill is missed at any time, and no intercourse occurred in the past 5 days, two pills should be taken immediately and a backup contraceptive method should be used for 7 days

    • If an active pill is missed at any time, and intercourse occurred in the previous 5 days, emergency ("Plan B") contraception should be used immediately, and the combination pills restarted the following day; a backup contraceptive method should be used for 5 days

  • Another regimen involves taking a combination pill continuously with no regular menses; at the end of one years' use, 58% of the women had amenorrhea, and nearly 80% reported no bleeding requiring sanitary protection

  • Studies have not shown any significant risk from long-term amenorrhea for patients taking this continuous oral contraceptive regimen

Benefits

• There are many noncontraceptive advantages to oral contraceptives

  • Menstrual flow is lighter

  • Decreased risk of ovarian and endometrial cancer

  • Improvement in acne

  • Dysmenorrhea, pain with ovulation and postovulatory aching are relieved for most women

  • Functional ovarian cysts generally disappear with oral contraceptive use, and new cysts do not occur

  • Frequency of uterine myomas is lower in long-term users (> 4 years)

  • There is also a beneficial effect on bone mass

• Selection

  • Any of the "low-dose" combination oral contraceptives (containing 35 mcg or less of ethinyl estradiol or 3 mg of estradiol valerate) are suitable for most women

  • There is some variation in potency of the various progestins in the low-dose pills, but this variation results in essentially no clinically significant differences for most women

  • Women who have acne or hirsutism may benefit from use of one of the pills containing the third-generation progestins, desogestrel or norgestimate, since they are the least androgenic

  • The low-dose oral contraceptives commonly used in the United States are listed in Table 18–2

• Drug interactions

  • Drugs that interact with oral contraceptives to decrease their efficacy include

    • Phenytoin

    • Phenobarbital (and other barbiturates)

    • Primidone

    • Topiramate

    • Carbamazepine

    • Rifampin

    • St. John's wort

  • Women taking these drugs should use another means of contraception for maximum protection

  • Antiretroviral medications, specifically ritonavir-boosted protease inhibitors, may significantly decrease the efficacy of combined oral contraceptives, and the concomitant use of oral contraceptives may increase the toxicity of these antiretroviral agents

  • Non-nucleoside reverse transcriptase inhibitors have smaller effects on oral contraceptive efficacy, while nucleoside reverse transcriptase inhibitors appear to have no effect

• Contraindications and adverse effects

  • See Table 18–3

• Minor side effects

  • Nausea and dizziness may occur in the first few months of pill use

  • Weight gain of 2–5 lb (0.9–2.25 kg) commonly occurs

  • Spotting or breakthrough bleeding between menstrual periods may occur, especially if a pill is skipped or taken late; this may be helped by switching to a pill of slightly greater estrogenic potency or by switching to a triphasic pill regimen

  • Missed menstrual periods may occur, especially with low-dose pills

  • Fatigue and decreased libido can occur

  • Chloasma may occur

• "Minipill" alternative formulation

  • A formulation containing 0.35 mg of norethindrone is available in the United States

  • Efficacy is similar to that of combined oral contraceptives, with failure rates of 1–4%

  • This so-called "minipill" is begun on the first day of a menstrual cycle and then taken continuously for as long as contraception is desired

• Advantages

  • The low dose of progestin and absence of estrogen make the minipill safe during lactation; it may increase the flow of milk

  • It is often tried by women who want minimal doses of hormones and by patients who are over age 35

  • It can be used by women with uterine myomas or sickle cell disease (hemoglobin S/S or S/C)

• Complications and contraindications

  • Minipill users often have bleeding irregularities (eg, prolonged flow, spotting, or amenorrhea); such patients may need monthly pregnancy tests

  • Ectopic pregnancies are more frequent in minipill users, and complaints of abdominal pain should be investigated with this in mind

  • The contraindications listed in Table 18–3 apply to the minipill

  • Minor side effects of combination oral contraceptives such as weight gain and mild headache may also occur with the minipill

Contraceptive injections and implants

• Medroxyprogesterone acetate: Long-acting progestins

  • The progestin, medroxyprogesterone acetate, is given intramuscularly, at 150 mg every 3 months

  • Depot medroxyprogesterone acetate (DMPA), is now available as a new 104 mg subcutaneous preparation in the United States

  • Medroxyprogesterone acetate has a contraceptive efficacy of 99.7%

  • Common side effects

    • Irregular bleeding

    • Amenorrhea

    • Weight gain

    • Headache

  • Users commonly have irregular bleeding initially and then often subsequently develop amenorrhea

  • Ovulation may be delayed after the last injection

  • Contraindications are similar to those for the minipill

• Nexplanon

  • A 40-mm by 2-mm rod containing 68 mg of the progestin etonogestrel that is inserted in the inner aspect of the nondominant arm

  • Remains effective for 3 years

  • Hormone levels drop rapidly after removal, and there is no delay in the return of fertility

Other hormonal methods

• A transdermal contraceptive patch containing 150 mcg norelgestromin and 20 mcg ethinyl estradiol and measuring 20 cm² is available

  • The patch is applied to the lower abdomen, upper torso, or buttock once a week for 3 consecutive weeks, followed by 1 week without the patch

  • The mechanism of action and efficacy are similar to those associated with oral contraceptives, though compliance may be better

  • It appears that the average steady-state concentration of ethinyl estradiol with the patch is approximately 60% higher than with a 35-mcg pill; however, there is currently no evidence for an increased incidence of estrogen-related side effects

• A contraceptive vaginal ring that releases 120 mcg of etonogestrel and 15 mcg of ethinyl estradiol daily is available

  • The ring is soft and flexible and is placed in the upper vagina for 3 weeks, removed, and replaced 1 week later or can be removed and replaced after 4 weeks for continuous cycling, similar to oral contraceptives

  • The efficacy, mechanism of action, and systemic side effects are similar to those associated with oral contraceptives

  • In addition, users may experience an increased incidence of vaginal discharge

Follow-Up

• Patients using hormonal contraception are usually seen annually for a review of pertinent history, breast and pelvic examination with Papanicolaou smear

Complications

• Serious complications of combined hormonal contraception include

• Venous thromboembolism: 15/100,000 annually

• Myocardial infarction: 40/100,000 annually in smokers over age 35

• Hypertension: 1% incidence