Drugs Acting on the Uterus

• Drugs acting on the uterus play pivotal roles in various obstetric and gynecological settings, including labor induction, management of postpartum hemorrhage, prevention of preterm labor, and medical abortion.
• Drugs Acting on the Uterus: Include oxytocics (stimulate contraction) and tocolytics (inhibit contraction).

1. Uterine Stimulants (Oxytocics):

1. Oxytocin:

   • Source: Produced in the hypothalamus, secreted by the posterior pituitary.
   • Actions: Stimulates uterine contractions and milk ejection.
   • Uses: Induction of labor, postpartum hemorrhage control.
   • Side Effects: Uterine hyperstimulation, fetal distress, water intoxication (ADH-like effect).

2. Ergot Alkaloids (Methylergonovine):

   • Mechanism: Stimulates sustained uterine contractions.
   • Uses: Postpartum hemorrhage control.
   • Side Effects: Hypertension, nausea, vomiting, headache.

3. Prostaglandins (e.g., Dinoprostone, Misoprostol):

   • Mechanism: Cause cervical ripening and stimulate uterine contractions.
   • Uses: Labor induction, medical abortion (with mifepristone), postpartum hemorrhage.
   • Side Effects: GI disturbances (nausea, diarrhea), uterine hypertonus, fetal distress.

2. Uterine Relaxants (Tocolytics):

1. Beta-2 Agonists (e.g., Terbutaline):

   • Mechanism: Relax uterine smooth muscle.
   • Uses: Delay preterm labor (short-term).
   • Side Effects: Tachycardia, hyperglycemia, hypokalemia.

2. Calcium Channel Blockers (e.g., Nifedipine):

   • Mechanism: Inhibit calcium entry, reducing uterine contractions.
   • Uses: Preterm labor.
   • Side Effects: Hypotension, headache, flushing.

3. NSAIDs (e.g., Indomethacin):

   • Mechanism: Inhibit prostaglandin synthesis, reducing contractions.
   • Uses: Short-term tocolysis.
   • Side Effects: Premature ductus arteriosus closure, oligohydramnios.

4. Magnesium Sulfate:

   • Mechanism: Relaxes uterine muscles and provides fetal neuroprotection.
   • Uses: Preterm labor, seizure prevention in eclampsia.
   • Side Effects: Respiratory depression, hypotension, cardiac arrhythmias.

3. Other Uterine Agents:

1. Progesterone Agonists (e.g., Progesterone, Dydrogesterone):

   • Uses: Support pregnancy and prevent preterm labor.

2. Antiprogestins (e.g., Mifepristone):

   • Uses: Medical abortion and hyperprolactinemia management.

Clinical Applications of Uterine Drugs:

• Labor Induction and Augmentation: Ensures timely and effective delivery.
• Postpartum Hemorrhage Management: Prevents and controls excessive bleeding.
• Preterm Labor Management: Delays delivery for fetal maturation.
• Medical Abortion: Non-surgical pregnancy termination.
• Pregnancy Support: Maintains pregnancy in high-risk cases.

Side Effects and Considerations:

• Uterotonics: Risk of uterine hyperstimulation, fetal distress, maternal hypertension.
• Uterine Relaxants: Cardiovascular effects, maternal hypoxia, electrolyte imbalances.
• General Considerations: Monitor maternal and fetal well-being; avoid in contraindications like cardiovascular disease and fetal anomalies.

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