What are low-dose birth control pills?

Low-Dose Birth Control Pills

Low-dose birth control pills are combined oral contraceptives (COCs) that contain 35 μg or less of ethinyl estradiol along with a progestin component. 1, 2

Composition and Types

• Low-dose COCs contain ethinyl estradiol (EE) in doses ranging from 10-35 μg, combined with various progestins 2
• Progestins in COCs are categorized by generations:
  • First-generation: norethindrone, ethynodiol diacetate 2
  • Second-generation: levonorgestrel, norgestrel 2
  • Third-generation: norgestimate, desogestrel 2
  • Fourth-generation: drospirenone, dienogest 2
• Standard pill packs include 28 pills total, with 21-24 hormone pills and 4-7 placebo (hormone-free) pills 1
• COCs are available in fixed-dose monophasic regimens (same dose throughout) or phasic regimens (varying doses) 1

Common Formulations

• Many providers begin with a monophasic pill containing 30-35 μg of ethinyl estradiol and a progestin such as levonorgestrel or norgestimate 1
• Newer formulations include:
  • Drospirenone-containing pills, which have anti-mineralocorticoid effects that may help mitigate blood pressure increases 1
  • Pills containing natural estrogens (estradiol valerate, estetrol) instead of ethinyl estradiol 1

Effectiveness and Safety

• Low-dose COCs are highly effective when used correctly, with a typical-use failure rate of approximately 9% 1
• The most serious adverse event associated with COC use is the increased risk of blood clots (venous thromboembolism), which increases from 1 per 10,000 to 3-4 per 10,000 woman-years during COC use 1, 2
• This risk is still significantly lower than the risk during pregnancy (10-20 per 10,000 woman-years) 1
• The FDA recommends that new users of oral contraceptives should be started on preparations containing 0.035 mg (35 μg) or less of estrogen 3, 4
• Lower doses of ethinyl estradiol are recommended to minimize potential increased stroke risk 2

Benefits Beyond Contraception

• Decreased menstrual cramping and blood loss 1
• Improvement in acne through anti-androgenic properties 1, 2
• Beneficial for medical conditions such as:
  • Anemia 1
  • Severe dysmenorrhea 1
  • Endometriosis 1
  • Abnormal uterine bleeding 1
  • Von Willebrand and other bleeding disorders 1
• Extended or continuous cycle regimens can be useful for conditions exacerbated cyclically, such as migraines without aura, epilepsy, and irritable bowel syndrome 1
• Long-term use (>3 years) provides significant protection against endometrial and ovarian cancers 1

Contraindications and Cautions

• COCs should not be prescribed for patients with:
  • Severe and uncontrolled hypertension 2
  • Ongoing hepatic dysfunction 2
  • Complicated valvular heart disease 2
  • Migraines with aura or focal neurologic symptoms 2
  • Thromboembolism or thrombophilia 2
  • Complications of diabetes 2
• While smoking should be discouraged, it is not a contraindication to COC use in individuals younger than 35 years old 2

Clinical Pearls

• COCs can be started on the same day as the visit ("quick start") in healthy, non-pregnant individuals, with a backup method used for at least the first 7 days 1
• Among low-dose pills, there are no clear data suggesting one formulation is superior to another for most users 1
• The absolute risk of venous thromboembolism associated with COC use is small compared to the risk during pregnancy 2
• For patients with specific stroke risk factors, progestin-only contraception or nonhormonal contraception may be more appropriate 2
• The CDC recommends prescribing up to 1 year of COCs at a time 2

Potential Adverse Effects

• The most common adverse effect of extended-cycle regimens is unscheduled bleeding 1
• Other common transient adverse effects include headache and nausea 1
• Weight gain and mood changes have not been reliably linked to COC use 1
• Drug interactions may reduce effectiveness, particularly with certain antiretroviral agents 2