This document summarizes various drugs used for induction and augmentation of labor, including oxytocics, prostaglandins, and ergot alkaloids. Oxytocin works by increasing uterine contractions and is the drug of choice for labor induction and treatment of uterine inertia. Prostaglandins like misoprostol and dinoprostone promote contractions and cervical ripening. Side effects include nausea and vomiting. Ergot alkaloids like ergometrine and methylergometrine also increase contractions but can increase blood pressure and should be avoided in patients with vascular or renal issues.

1. Uterine Stimulants
FOR BNS IST YEAR
DR. PRAVIN PRASAD
IST YEAR RESIDENT, MD CLINICAL PHARMACOLOGY
MAHARAJGUNJ MEDICAL CAMPUS
2ND OCTOBER, 2015(ASOJ 15, 2072); FRIDAY

2. Drugs Used For Induction and
Augmentation of Labour
 Also known as Oxytocics, Abortifacients
 Classified as:
 Posterior Pitutary Hormone: Oxytocin, Desamino oxytocin
 Prostaglandins: PGE2, PGE1, PGF2α ,15-methyl PGF2α(Carboprost),
Misoprostol (Methyl ester of PGE1)
 Ergot Alkaloids: Ergometrine (Ergonovine), Methylergometrine,
 Miscellaneous: Ethacridine, Quinine
 Anti Progestin: Mifepristone

3. Oxytocin
1. Effects on Uterus:
 Increases force and frequency of
uterine contraction
 Response of uterus varies
2. Effects on Breast:
 Contracts myoepithelium of
mammary alveoli.
3. Cardiovascular System (CVS):
 Higher Dose: brief fall in blood
pressure, reflex tachycardia,
flushing
4. Kidney:
 ADH like action at high doses
(pulmonary edema at high doses
of oxytocin with large amounts of
intravenous fluids)

4. Oxytocin
 Mechanism of Action:
 Action mediated through specific G-protein coupled oxytocin receptors
 On Activation, these receptors mediate the response:
 By depolarization of muscle fibres and influx of Ca++ ions (main mechanism)
 Through phosphoinsitide hydrolysis and IP3 mediated intracellular release of Ca++ ions.
 Number of oxytocin receptors increases markedly during later part of
pregnancy
 Also increases Prostaglandin (PG) synthesis and release by the
endometrium

5. Oxytocin
Uses
 Drug of Choice
 Induction of Labour (slow i.v.
infusion 5IU in 500 ml glucose or NS;
10milli IU/mL: 0.2-2.0 mL/min)
 Uterine Inertia
 Postpartum Haemorrhage
 Breast Engorgement (inefficient
milk ejection reflex; intra-nasally)
 Oxytocin Challenge Test (risky and
rarely performed)
Side Effects
 Injudicious use: maternal and
foetal soft tissue injury, ruptured
uterus, foetal asphyxia/death
 Water intoxication

6. Prostaglandins
 Local Hormones, derived from breakdown of membrane phospholipid
(yielding arachidonic acid)
 PGE2 and PGF2α: commonly used clinically
 Dinoprostone (PGE2): cervical maturation/ripening (collagenolytic proterty);
5 times potent than and less toxic than PGF2α; costly
 Dinoprost tromethammine(PGF2α): myometrial contractility
 Promotes myometrial contraction irrespective of duration of gestation
 Mechanism of Action:
 Change in myometrial cell membrane permeability and/or alteration of membrane
bound Ca++
 Also sensitizes uterus to oxytocin

7. Prostaglandins: Uses
 Misoprostol PGE1: induction of abortion/labour; cervical ripening
 Termination of molar pregnancy
 Induction of labour (poor preinduction cervical score as in Intrauterine Fetal Death,
shorter period of gestation, early primigravida: PGE1)
 Acceleration of labour
 Cervical ripening for induction of labour/abortion
 Management of atonic postpartum haemonrrrhage
 Refractive cases of Atonic uterus
 Medical management of tubal ectopic pregnancy

8. Prostaglandins: Side Effects
 On systemic use:
 Nausea, vomiting, diarrhoea, pyrexia, bronchospasm
 Cervical laceration when used as an abortifacient
 Tachysystole of uterus during induction
 Meconium passage by foetus (Foetal Distress)
 Rupture of uterus: Rare
 Should not be used in patients with previous history of Caesarean
Section

9. Ergot Alkalodis
 Ergometrine and Methylergometrine
 Uterus:
 Force, frequency and duration of uterine contraction increased
 Low dose phasic response; high dose contracture seen
 Gravid, (near) term and early puerperal uterus more sensitive
 Polarity of uterus not maintained
 Mechanism of action: partial agonistic action on 5-HT2 and alpha adrenergic receptors
 CVS:
 Weak vasoconstrictors
 Can raise blood pressure
 Gastrointestinal Tract:
 Increased peristalsis

10. Ergot Alkalodis
Uses
 Control and Prevent
Postpartum Haemorrhage
 After Caesarean
Section/Instrumental
Delivery- to prevent uterine
atony
 To ensure normal involution
Side Effects
 Nausea, vomiting
 Rise in blood pressure
 Decrease milk secretion if used n
higher dose for many days
postpartum
 Should be avoided in patients with:
 Vascular disease
 Presence of sepsis
 Liver and Kidney Disease