What are OCP (Oral Contraceptive Pills)?

Oral Contraceptive Pills (OCPs): Overview and Clinical Considerations

Oral contraceptive pills (OCPs) are hormonal medications primarily used for pregnancy prevention, with additional therapeutic benefits for various medical conditions including menstrual disorders, endometriosis, and polycystic ovarian syndrome.

Types of OCPs

OCPs are broadly categorized into two main types:

1. Combined Oral Contraceptives (COCs)

   • Contain both estrogen (typically ethinyl estradiol) and progestin
   • Modern formulations contain low-dose ethinyl estradiol (≤35 μg)
   • Classified by progestin generations:
     • First generation: Norethindrone
     • Second generation: Levonorgestrel
     • Third generation: Desogestrel, gestodene
     • Fourth generation: Drospirenone, dienogest

2. Progestin-Only Pills (POPs)

   • Contain only progestin without estrogen
   • Options include norethindrone, drospirenone, and norgestrel (recently approved as first OTC oral contraceptive in the US) 1

Mechanism of Action

OCPs prevent pregnancy through multiple mechanisms 2, 3:

• Primary mechanism: Inhibition of ovulation by suppressing gonadotropins
• Secondary mechanisms:
  • Thickening of cervical mucus (impedes sperm entry)
  • Endometrial changes (reduces likelihood of implantation)

Efficacy

• With perfect use, OCPs have failure rates of 0.5-1% 4
• With typical use, pregnancy rates are 4-7% per year 4
• COCs are the most commonly used reversible contraceptive method in the US (21.9% of all contraception) 4

Clinical Benefits Beyond Contraception

OCPs offer numerous non-contraceptive health benefits 2, 5:

• Established benefits:

  • Protection against ovarian and endometrial cancers
  • Reduced risk of benign breast disease
  • Decreased risk of pelvic inflammatory disease
  • Prevention of ectopic pregnancy
  • Reduction in iron-deficiency anemia

• Therapeutic uses:

  • Treatment of dysmenorrhea
  • Management of irregular or excessive bleeding
  • Improvement in acne and hirsutism
  • Relief of endometriosis-associated pain

Safety Considerations and Contraindications

First and second generation progestins (levonorgestrel, norethindrone) combined with low-dose ethinyl estradiol (≤35 μg) have the most favorable risk profile among combined hormonal methods 6.

Major contraindications for COCs 6, 3:

• History of venous thromboembolism or arterial thrombotic disease
• Breast or endometrial carcinoma
• Undiagnosed abnormal genital bleeding
• Severe hypertension (SBP ≥160 or DBP ≥100)
• Diabetes with vascular involvement
• Migraine with aura
• Liver tumors or active liver disease
• Age ≥35 years who smoke

Cardiovascular Risk Considerations

• Baseline VTE risk in non-users: 1 per 10,000 woman-years
• VTE risk with COCs: 3-4 per 10,000 woman-years 6
• Third generation COCs containing desogestrel are associated with approximately two-fold increased risk of VTE compared to second generation pills 3
• Hypertension is one of the most common potential contraindications to OCP use 2
  • Approximately 10% of reproductive-aged women have SBP ≥140 or DBP ≥90
  • Almost 20% have SBP ≥130 or DBP ≥80

Special Populations

Women at High Risk for HIV

• Evidence from observational studies shows some association between progestin-only injectable contraceptives and risk of HIV acquisition, but causality remains unclear 2
• Studies of levonorgestrel implants did not suggest elevated HIV risk 2
• Most studies found no statistically significant association between COCs and HIV acquisition 2

Breastfeeding Women

• COCs are generally not recommended in the first month postpartum for breastfeeding women (Category 3) 2
• After 1 month postpartum, COCs may be used with caution (Category 2) 2

Drug Interactions

Effectiveness of OCPs may be reduced when used with 6:

• Anticonvulsants
• Certain antimicrobials
• HIV protease inhibitors
• St. John's wort

Clinical Pearls

• Formulation matters: Differences between therapeutically equivalent and brand-name low-dose OCPs may affect contraceptive efficacy and breakthrough bleeding 7
• Bleeding patterns: Breakthrough bleeding is one of the most common reasons for OCP discontinuation, which can lead to use of less effective methods or no method at all 7
• Extended-cycle regimens (fewer or no inactive pills) may benefit conditions like anemia, severe dysmenorrhea, endometriosis, and migraines without aura 6
• Monitoring: Blood pressure should be monitored in all OCP users, as even small increases in blood pressure can occur with OCP use 2

Recent Developments

In July 2023, norgestrel (Opill) became the first over-the-counter oral contraceptive pill approved in the United States, potentially increasing access to contraception, especially for younger women and those with limited healthcare access 1.