Pharmacology Cheat Sheet
Contraception, Fertility and Uterine Tone
Reproductive pharmacology for NEET-PG: contraceptive mechanisms, Centchroman, carboprost asthma contraindication, tocolytics, and magnesium antidote.
MedNext Academy | 3 min read
Clinically reviewed by Dr Shameer Deen, MBBS, MS, MRCS
Contraception, Fertility and Uterine Tone
Reproductive pharmacology for NEET-PG: contraceptive mechanisms, Centchroman, carboprost asthma contraindication, tocolytics, and magnesium antidote.
Reproductive pharmacology covering oral contraceptives, emergency contraception, ovulation induction, uterotonics, and tocolytics.
High-yield lines
- In combined oral contraceptives, oestrogen suppresses FSH and follicular development, while progestogen suppresses the LH surge to prevent ovulation.
- Rifampicin is a potent CYP3A4 inducer that dramatically reduces oral contraceptive efficacy, so a copper IUD is preferred for women on it.
- Levonorgestrel emergency contraception works by delaying ovulation and is ineffective once ovulation has occurred.
- The copper IUD is the single most effective method of emergency contraception at over 99% efficacy.
- Centchroman (ormeloxifene, marketed as Saheli) is the only once-weekly non-steroidal SERM oral contraceptive, developed in India.
- Clomiphene is a SERM that blocks hypothalamic oestrogen feedback to raise FSH and LH, inducing ovulation.
- Ovarian hyperstimulation syndrome is the most dangerous complication of ovulation induction and is mediated by VEGF.
- Oxytocin 10 IU intramuscularly is the globally preferred prophylactic uterotonic for active management of the third stage of labour.
- Carboprost (PGF2-alpha) is absolutely contraindicated in asthma because it causes bronchospasm.
- Ergometrine is contraindicated in hypertension, distinguishing it from oxytocin and misoprostol which are safe in asthmatics.
- Nifedipine is the preferred first-line tocolytic, while atosiban is the most uterus-specific.
- Indomethacin as a tocolytic is avoided after 32 weeks due to premature closure of the ductus arteriosus.
- The purpose of tocolysis is to buy about 48 hours to administer antenatal corticosteroids for fetal lung maturity.
- The antidote for magnesium sulfate toxicity is intravenous calcium gluconate.
Mapped competency codes
- PH1.39
- PH1.40
- PH1.41
Continue into the full chapter
This summary maps to PH10-reproductive-pharmacology.
Frequently Asked Questions
Which uterotonic is contraindicated in asthma?
Carboprost (PGF2-alpha), because it causes bronchospasm; oxytocin and misoprostol are safe in asthmatics.
What is Centchroman?
Ormeloxifene, the only once-weekly non-steroidal SERM oral contraceptive, developed in India and marketed as Saheli.
Why does rifampicin reduce contraceptive efficacy?
It is a potent CYP3A4 inducer that accelerates hormone metabolism, so a copper IUD or LNG-IUS is preferred.
What is the antidote for magnesium sulfate toxicity?
Intravenous calcium gluconate 10%.
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