Classify hormonal contraceptives. Describe the contraindications of oral contraceptive pill.
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Classification of Hormonal Contraceptives
Hormonal contraceptives are broadly divided into two categories based on their hormonal composition:
I. Combination Hormonal Contraceptives (Estrogen + Progestin)
These contain ethinyl estradiol (estrogen) combined with a synthetic progestin. They act by providing negative feedback: estrogen blunts FSH release (preventing follicular development), progestin inhibits LH secretion (preventing ovulation), and progestin also thickens cervical mucus to hinder sperm penetration.
A. Combination Oral Contraceptives (COCs)
| Type | Description |
|---|---|
| Monophasic | Constant fixed dose of estrogen + progestin throughout the active pill days |
| Biphasic | Two different doses of hormones across the cycle |
| Triphasic | Constant estrogen with incrementally increasing progestin doses - attempts to mimic the natural cycle |
| Four-phasic | Varying doses of estradiol valerate + dienogest across 28 days (only 2 placebo days) |
| Extended-cycle | 84 active pills + 7 placebo days - withdrawal bleeding only 4x/year |
| Continuous | Active pills every day - no withdrawal bleeding |
B. Transdermal Patch
- Contains ethinyl estradiol + norelgestromin (or levonorgestrel)
- One patch per week for 3 weeks; no patch in week 4 (withdrawal bleeding occurs)
- Efficacy comparable to oral COCs, but less effective in women >90 kg
- Total estrogen exposure is higher than with oral COCs, raising VTE risk
- Contraindicated in BMI ≥30 kg/m²
C. Vaginal Ring (NuvaRing)
- Contains ethinyl estradiol + etonogestrel
- Inserted for 3 weeks; removed for week 4 (withdrawal bleeding)
- Most common reason for discontinuation: vaginal irritation or ring expulsion
II. Progestin-Only Contraceptives
Preferred in women who are breastfeeding, have contraindications to estrogen, or are older smokers. (Note: estrogen binds prolactin receptors and reduces milk production, while progestins do not.)
| Method | Agent | Notes |
|---|---|---|
| Mini-pill (POP) | Norethindrone (or drospirenone) | Daily pill; less effective than COCs; irregular cycles common |
| Injectable | Medroxyprogesterone acetate (DMPA) | IM or SC every 3 months; causes amenorrhea; delayed return of fertility; risk of bone loss (do not continue >2 years unless necessary) |
| Subdermal Implant | Etonogestrel | Lasts up to 3 years; as reliable as sterilization; irregular bleeding; LARC method |
| Levonorgestrel IUD | Levonorgestrel | 3-7 years; also effective for heavy menstrual bleeding; avoid with PID or history of ectopic pregnancy; LARC method |
III. Postcoital / Emergency Contraceptives
- Levonorgestrel (Plan B): within 72 hours of unprotected intercourse
- Ulipristal acetate: selective progesterone receptor modulator; effective up to 120 hours
- Copper IUD: most effective EC method; also provides long-term contraception
IV. Non-Hormonal (for context)
Condom, diaphragm, contraceptive sponge, copper IUD - not hormonal but complete the contraceptive spectrum.
Contraindications to the Oral Contraceptive Pill (OCP)
Absolute Contraindications
| Condition | Rationale |
|---|---|
| Pregnancy | Teratogenic risk; no benefit |
| Current or past thromboembolic disease (DVT, PE, thrombophlebitis) | Estrogen increases clotting factors and VTE risk |
| Factor V Leiden mutation carriers | Markedly amplified VTE risk with exogenous estrogen |
| Cerebrovascular accident (stroke) - history of | Further thrombotic/embolic risk |
| Coronary artery disease | Estrogen-mediated cardiovascular risk |
| Known or suspected breast carcinoma | Estrogen-dependent tumor growth |
| Known or suspected estrogen-dependent neoplasia (e.g., endometrial cancer) | Tumor stimulation |
| Liver neoplasia (benign or malignant) | Estrogen is hepatotrophic; promotes growth of hepatic adenomas |
| Acute phase mononucleosis | Hepatic involvement risk |
Relative Contraindications
| Condition | Rationale |
|---|---|
| Hypertension ≥140/90 mmHg on three visits, or diastolic >110 mmHg at one visit | Estrogen raises blood pressure |
| Impaired liver function | OCPs are hepatically metabolized; cholestasis risk |
| Breastfeeding / Lactation | Estrogen suppresses prolactin receptors and reduces milk production (progestin-only preferred) |
| Undiagnosed abnormal vaginal bleeding | Must exclude endometrial pathology first |
| Previous cholestasis during pregnancy | Indicates susceptibility to estrogen-induced cholestasis |
| Major surgery planned within 4 weeks | Perioperative VTE risk |
| Major injury or immobilization of lower extremities | Prolonged immobility + estrogen = high VTE risk |
| Completion of term pregnancy within previous 3 weeks | Hypercoagulable post-partum state |
Additional Clinically Important Contraindications (WHO/CDC MEC)
- Cigarette smoking in women ≥35 years: Synergistic thrombotic and cardiovascular risk - absolute contraindication for COCs
- Migraine with aura: Increased ischemic stroke risk with estrogen
- Uncontrolled diabetes with vascular disease: Estrogen adversely affects lipids and vascular endothelium
- Active gallbladder disease: Estrogen affects bile composition, increasing gallstone risk
- Severe (decompensated) cirrhosis: Impaired hepatic metabolism of steroids
Mechanism Summary
"Exogenously administered estrogen provides negative feedback that blunts FSH release by the pituitary gland, and progestin inhibits LH secretion, thus preventing ovulation. Progestin also thickens cervical mucus, hindering sperm from reaching the ovum."
- Lippincott Illustrated Reviews: Pharmacology
Sources:
- Lippincott Illustrated Reviews: Pharmacology, Chapter 25 (Hormonal Contraceptives)
- Textbook of Family Medicine, 9e, Chapter 26 (Table 26-4: Contraindications to OCPs)
- Berek & Novak's Gynecology (Oral Contraceptives in dysmenorrhea and gynecologic management)
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