📘 PHARMACOLOGY IN OBSTETRICS AND GYNECOLOGY (OBG)

(Highly Important for GNM, BSc Nursing, NHM, AIIMS, NORCET, GPSC, and Staff Nurse Exams)

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✅ 1. Introduction

Pharmacology in Obstetrics and Gynecology involves the study of drugs used in the management of pregnancy, childbirth, and female reproductive disorders. It includes medications that affect the uterus, hormones, fetal development, and gynecologic conditions.

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✅ 2. Categories of Drugs Used in OBG

Drug Category	Common Uses in OBG	Examples
Uterotonics	Induce labor, control postpartum bleeding	Oxytocin, Misoprostol, Ergometrine
Tocolytics	Suppress preterm labor	Nifedipine, Salbutamol, Indomethacin
Hormonal Drugs	Menstrual disorders, contraception	Progesterone, Estrogen, Clomiphene
Antibiotics	Treat infections (UTI, STDs, puerperal sepsis)	Ampicillin, Metronidazole, Ceftriaxone
Antihypertensives in Pregnancy	Manage gestational hypertension or preeclampsia	Labetalol, Methyldopa, Nifedipine
Antiemetics	Manage nausea and vomiting in pregnancy	Ondansetron, Doxylamine, Promethazine
Anticonvulsants (eclampsia)	Prevent seizures	Magnesium sulfate, Diazepam
Iron and Hematinics	Treat anemia	Ferrous sulfate, Folic acid
Calcium Supplements	Prevent preeclampsia, support fetal bones	Calcium carbonate, Vitamin D3
Anti-D Immunoglobulin	Prevent Rh incompatibility	Rho(D) immune globulin
Ovulation Inducers	Infertility treatment	Clomiphene citrate, Letrozole
Antifungals & Antivirals	Vaginal infections	Fluconazole, Acyclovir

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✅ 3. Important Obstetric Drugs and Their Uses

🔹 Oxytocin

• Use: Induces labor, augments labor, controls postpartum hemorrhage
• Route: IV/IM
• Caution: Continuous fetal monitoring required

🔹 Misoprostol (Prostaglandin E1 Analog)

• Use: Cervical ripening, medical abortion, PPH control
• Route: Oral/Vaginal/Rectal
• Side Effect: Uterine hyperstimulation

🔹 Magnesium Sulfate

• Use: Anticonvulsant in eclampsia
• Toxicity Signs: Respiratory depression, loss of deep tendon reflexes
• Antidote: Calcium gluconate

🔹 Methyldopa / Labetalol / Nifedipine

• Use: Safe antihypertensives in pregnancy
• Avoid: ACE inhibitors and ARBs (contraindicated in pregnancy)

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✅ 4. Hormonal Pharmacology in Gynecology

Drug	Use
Clomiphene Citrate	Induction of ovulation in infertility
Letrozole	Aromatase inhibitor – PCOS infertility
Medroxyprogesterone	Dysfunctional uterine bleeding
Oral Contraceptives	Birth control, menstrual irregularities

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✅ 5. Drug Contraindications in Pregnancy

Drug Class	Harm / Reason
ACE Inhibitors	Fetal renal damage
Tetracyclines	Teeth discoloration, bone deformity
Warfarin	Teratogenic – CNS & facial anomalies
Isotretinoin	Highly teratogenic
Thalidomide	Phocomelia (limb defects)

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✅ 6. Nurse’s Responsibilities in OBG Pharmacology

• Check gestational age before administering drugs
• Monitor vital signs, uterine activity, FHR
• Observe for drug side effects or signs of toxicity
• Ensure informed consent, especially in labor-inducing drugs
• Counsel about adherence to iron, calcium, folic acid

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✅ 7. Golden One-Liners for Revision

• Oxytocin is used for labor induction and postpartum bleeding control
• Magnesium sulfate is the drug of choice in eclampsia
• Clomiphene is the first-line agent for anovulatory infertility
• Misoprostol can be given orally, vaginally, or rectally
• ACE inhibitors are contraindicated during pregnancy

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✅ 8. Top 5 MCQs for Practice

1. Which drug is used to control postpartum hemorrhage?
a) Diazepam
b) Misoprostol
c) Ferrous sulfate
d) Doxycycline
Correct Answer: b) Misoprostol
Rationale: Misoprostol is a uterotonic used to contract the uterus and control bleeding.

2. The antidote for magnesium sulfate toxicity is:
a) Vitamin K
b) Atropine
c) Calcium gluconate
d) Naloxone
Correct Answer: c) Calcium gluconate
Rationale: It reverses the effects of magnesium toxicity such as respiratory depression.

3. Which of the following drugs is used as an ovulation inducer in PCOS?
a) Methyldopa
b) Letrozole
c) Propranolol
d) Fluconazole
Correct Answer: b) Letrozole
Rationale: Letrozole, an aromatase inhibitor, helps stimulate ovulation in women with PCOS.

4. Which antihypertensive is considered safe in pregnancy?
a) Enalapril
b) Losartan
c) Labetalol
d) Ramipril
Correct Answer: c) Labetalol
Rationale: Labetalol is a preferred beta-blocker in pregnancy; ACE inhibitors are contraindicated.

5. Which drug is contraindicated in pregnancy due to risk of teratogenicity?
a) Iron
b) Warfarin
c) Magnesium sulfate
d) Metronidazole
Correct Answer: b) Warfarin
Rationale: Warfarin crosses the placenta and causes developmental defects.