What are the types of oral birth control pills?

Types of Oral Birth Control Pills

Oral birth control pills are broadly categorized into two main types: combined oral contraceptives (COCs) and progestin-only pills (POPs), with various formulations and regimens available within each category. 1

Combined Oral Contraceptives (COCs)

Combined oral contraceptives contain both estrogen and progestin components and have a typical-use effectiveness rate of 91-95% 1. They work primarily by suppressing ovulation through inhibition of gonadotropins, while also creating changes in cervical mucus and the endometrium 2, 3.

Types of COC Formulations:

1. Based on Hormone Dosing Pattern:

   • Monophasic pills - Provide the same dose of estrogen and progestin in each active pill 4
   • Multiphasic pills (biphasic, triphasic) - Contain varying doses of hormones throughout the cycle 4

2. Based on Progestin Generation:

   • First-generation - Contain norethindrone or ethynodiol diacetate 5
   • Second-generation - Contain levonorgestrel or norgestrel 5
   • Third-generation - Contain norgestimate or desogestrel (less androgenic) 6
   • Fourth-generation - Contain drospirenone (a spironolactone analogue with antimineralocorticoid and antiandrogenic properties) 6, 3

3. Based on Estrogen Dose:

   • Standard dose - Containing 30-35 μg ethinyl estradiol
   • Low dose - Containing 20-25 μg ethinyl estradiol 5
   • Ultra-low dose - Containing less than 20 μg ethinyl estradiol

COC Regimens:

1. Standard Regimen - 21 active hormone pills followed by 7 hormone-free days (or 7 placebo pills) 6
2. 24/4 Regimen - 24 active hormone pills followed by 4 hormone-free days 7
3. Extended-Cycle Regimen - 84 active hormone pills followed by 7 hormone-free days (84/7), resulting in only 4 periods per year 7
4. Continuous Regimen - Active hormone pills taken continuously without a hormone-free interval, eliminating monthly bleeding 7

Progestin-Only Pills (POPs)

Progestin-only pills contain no estrogen and have a typical-use effectiveness rate of 87-99% 1. They work primarily by thickening cervical mucus and thinning the endometrial lining, with variable effects on ovulation.

Key Features of POPs:

• Must be taken at the same time each day (within a 3-hour window)
• All pills in the pack contain active hormones
• Particularly suitable for women who cannot take estrogen-containing contraceptives 6
• Common progestins used include norethindrone and desogestrel

Emergency Contraceptive Pills (ECPs)

While not used for regular contraception, these are important oral contraceptive options:

1. Levonorgestrel ECPs (Plan B) - Available over-the-counter, most effective when taken within 72 hours after unprotected intercourse, preventing approximately 75-80% of expected pregnancies 1

2. Ulipristal acetate (Ella) - Prescription-required, effective up to 120 hours after unprotected intercourse, preventing approximately 85% of expected pregnancies 1

Clinical Considerations for Selecting Oral Contraceptives

First-Line Options:

• For most patients requiring oral contraception, a COC containing ethinyl estradiol 20-30 mcg with a third or fourth generation progestin is recommended 1
• Pills containing levonorgestrel or norethisterone in combination with ethinyl estradiol 35 mcg or less are considered first-line due to their effectiveness, relatively low risk of venous thromboembolism, and availability 5

Special Considerations:

• Acne treatment - COCs containing drospirenone or other fourth-generation progestins have more potent antiandrogenic properties and are more effective for treating acne 6, 8
• Extended or continuous cycle regimens - Particularly beneficial for conditions like anemia, severe dysmenorrhea, endometriosis, and migraines without aura 6, 7
• Drug interactions - Rifampicin and rifabutin can reduce the effectiveness of POPs but do not affect the efficacy of injectable contraceptives like DMPA 6

Safety Considerations:

• COCs are contraindicated in women with a history of venous thromboembolism, stroke, coronary artery disease, migraine with aura, uncontrolled hypertension, or smokers ≥35 years 1
• The baseline incidence of venous thromboembolism in adolescents is up to 1 per 10,000 woman-years, with COCs increasing this risk three to fourfold 6
• POPs are generally safer for women with contraindications to estrogen 9

When prescribing oral contraceptives, it's important to select a pill with the lowest effective dose of estrogen and progestin that meets the patient's needs while considering both contraceptive and non-contraceptive benefits.