What is a low-dose form of estrogen for birth control?

From the Guidelines

Low-dose estrogen birth control options, such as pills containing 20-30 micrograms of ethinyl estradiol, are recommended to minimize potential increased stroke risk. According to the 2024 guideline for the primary prevention of stroke, lower doses of ethinyl estradiol are recommended to minimize potential increased stroke risk 1. The most common low-estrogen pills contain 20-30 micrograms of ethinyl estradiol, such as Lo Loestrin Fe (10 mcg), Alesse or Aviane (20 mcg), and Ortho-Cyclen or Sprintec (35 mcg) 1. These lower-dose options can reduce side effects like nausea, breast tenderness, and headaches while still providing effective contraception.

Key Considerations

• Low-estrogen contraceptives work by preventing ovulation, thickening cervical mucus to block sperm, and thinning the uterine lining to prevent implantation 1.
• The patch (Xulane) and vaginal ring (NuvaRing) are also low-dose options that deliver estrogen differently 1.
• While these methods are highly effective when used correctly, they must be taken consistently - pills at the same time daily, patches changed weekly, or rings replaced monthly 1.
• Some women may experience breakthrough bleeding initially, but this typically resolves within 2-3 months of use 1.
• Those with certain risk factors like smoking over age 35, history of blood clots, or certain types of migraines should discuss alternatives with their healthcare provider 1.

Recommendations

• In individuals considering combined hormonal contraception (CHC), lower doses of ethinyl estradiol are recommended to minimize potential increased stroke risk 1.
• In individuals with specific stroke risk factors (ie, age >35 years, tobacco use, hypertension, or migraine with aura) who are considering contraception, shared decision-making is recommended to determine the best contraceptive choice to balance the risk of stroke from contraception and the risk of stroke with pregnancy 1.
• Progestin-only contraception or nonhormonal contraception is reasonable to prevent the increased stroke risk associated with estrogen-containing contraception in individuals with specific stroke risk factors 1.

From the FDA Drug Label

New acceptors of oral contraceptive agents should be started on preparations containing 0. 035 mg or less of estrogen. The low form of estrogen for birth control is 0.035 mg or less of estrogen.

• Key points:
  • The dosage regimen prescribed should be one which contains the least amount of estrogen and progestogen that is compatible with a low failure rate and the needs of the individual patient.
  • Minimizing exposure to estrogen and progestogen is in keeping with good principles of therapeutics. 2

From the Research

Low-Dose Estrogen for Birth Control

• The use of low-dose estrogen for birth control has been studied in various forms, including extended-cycle oral contraceptives and transdermal contraceptive delivery systems 3, 4.
• One study found that an extended-cycle oral contraceptive with 20 μg of ethinyl estradiol and 100 μg of levonorgestrel, followed by 7 days of 10 μg of ethinyl estradiol, had a similar efficacy and adverse effect profile to other extended-regimen oral contraceptives 3.
• Another study compared a transdermal contraceptive delivery system containing ethinyl estradiol and levonorgestrel to a similar system containing ethinyl estradiol and norelgestromin, and found that the former had less estrogen exposure 4.
• The use of a levonorgestrel-releasing intrauterine device with transdermal estrogen replacement therapy has also been studied, and found to be effective in relieving climacteric symptoms and regulating bleeding patterns 5.
• Additionally, a study found that oral hormonal therapy with ethinylestradiol-levonorgestrel improved insulin resistance, obesity, and glycogen synthase kinase-3 in estrogen-deficient rats, independent of circulating mineralocorticoid 6.

Forms of Low-Dose Estrogen

• Extended-cycle oral contraceptives with low-dose estrogen, such as those containing 20 μg of ethinyl estradiol and 100 μg of levonorgestrel 3.
• Transdermal contraceptive delivery systems containing low-dose estrogen, such as those with ethinyl estradiol and levonorgestrel 4.
• Levonorgestrel-releasing intrauterine devices with transdermal estrogen replacement therapy 5.
• Oral hormonal therapy with ethinylestradiol-levonorgestrel 6.

Efficacy and Safety

• The efficacy and safety of low-dose estrogen for birth control have been studied in various clinical trials, with results showing similar efficacy and adverse effect profiles to other forms of hormonal contraception 3, 4.
• The use of low-dose estrogen has been found to improve insulin resistance, obesity, and glycogen synthase kinase-3 in estrogen-deficient rats, independent of circulating mineralocorticoid 6.
• However, the Pearl index of the transdermal contraceptive delivery system containing ethinyl estradiol and levonorgestrel is questionable, and compliance may be a potential confounder of the results 4.