• Agent that stimulate uterine contraction
• Physiological Roles:
• Milk ejection NOT production
• Contraction of the myoepithelium
• Only gravid uterus is responsive
• Receptor density increases at term
• Early on in pregnancy the uterus is not very responsive to oxytocin but responsiveness increases almost exponentially as the pregnancy continues
• May facilitate labor
• Oxytocin and ADH are similiar in structure:
• 2 AA difference
• 10% overlap with ADH activity which can cause water intoxication if oxytocin and fluids are given long periods of time
• Comes from the paraventricular nucleus
• Stimulus is mechanical stimulation of the breast, uterus or vagina
• Increases rate and force of uterine contractions

• Agents that stimulate uterine contraction
• Oxytocin
• Progstaglandins
• Prostaglandin E2 (dinoprostone)
• 15-methylprostaglandin F2
• Misoprostol
• Ergot Alkaloids
• Erogonovine
• Methylergonovine
• Mefipristone  

• Agents that relax the uterus 
• To prolong pregnancy until the fetus is viable
• Bedrest first then if:
• Premature Labor
• < 34 weeks
• Cervical dilation 3-4 cm
• No contraindications (e.g. pre-eclampsia)
• MGSO₄ (To reverse calcium gluconate )
• B₂ Adrenergic Agonists (Not a B₁ or non-specific B b/c we dont want to stimulate the heart)
• Indomethacin
• Niefedipine

• Mechanical stimulation of the breast, uterus, vagina OR auditory stimulation (crying baby) cause the pituitary to release oxytocin
• Oxytocin then acts on the breast for milk ejection and uterus for contractions. 

• Given either IV or IM
• Short plasma half life (5-15 mins)
• Allows for excellent control of uterine contractility using infusion during labor indection
• Post-partum blood loss can be minimized by injection of oxytocin to stimulate sustained contraction  

• More difficult to control- steeper dose-response relationship
• Contract BOTH the gravid and non-gravid uterus
• Prostaglandin E₂- Dinoprostone: Useful as abortifacient for ripening of the uterine cervix or for post-partum bleeding. Often admin by vaginal suppository
• 15-Methylprostaglandin F₂-Carboprost Tromethamine: IM
• Misoprostol 

• Derived from Claviceps pupurea 
• Fungus
• Produces many vasoactive and neurotransmitter substances
•  Ergonovine and Methylergonovine: IM or IV but difficult to control so used for post-partum bleeding control
• Not for induction of labor!!!!!!

In General: Only when the risks of continuing pregnancy are greater than the risks of induction

• Indications:
• Diabetes Mellitus
• History of intrauterine Demise
• Prolonged Pregnancy > 40 weeks
• HTN
• Bleeding complications
• Preeclampsia (HTN, edema, proteinuria)
• Contraindications:
• If vaginal delivery is NOT desirable DO NOT induce
• Fetopelvic disproportion
• Unfavorable presentation
• Invasive cervical CA

• Ripening of cervix: Softening and dialtion
• Don't want to contract against a constricted uterine cervix
• Use small doses of Dinoprostone intravaginally
• Oxytocin Challenge Test: Stress Test
• Oxy to contract: If fetal heart rate slows indication of fetal distress
• Post-Partum Bleeding Control
• Abortion: Prostaglandins with or without RU-486
• Remember RU-486 works by inhibiting uterine quieting effect of progesterone
• Prostaglandins cause contraction of both the gravid and non-gravid uterus  

Uterine tetany- Fetal Death or Uterine Rupture

Water intoxication (ADH activity)