Uterine stimulants

Lecture Classes for BNS 1st Year
Maharajgunj Nursing Campus

1. Uterine Stimulants For BNS I st Year Dr. Pravin Prasad I st Year Resident, MD Clinical Pharmacology Maharajgunj Medical Campus 2 nd 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: PGE 2 , PGE 1 , PGF 2 α ,15-methyl PGF 2 α ( Carboprost ), Misoprostol (Methyl ester of PGE 1 ) Ergot Alkaloids: Ergometrine ( Ergonovine ), Methylergometrine , Miscellaneous: Ethacridine , Quinine Anti Progestin: Mifepristone

3. Oxytocin Effects on Uterus: Increases force and frequency of uterine contraction Response of uterus varies Effects on Breast: Contracts myoepithelium of mammary alveoli. Cardiovascular System (CVS): Higher Dose: brief fall in blood pressure, reflex tachycardia, flushing 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 IP 3 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) PGE 2 and PGF 2 α : commonly used clinically Dinoprostone (PGE 2 ): cervical maturation/ripening ( collagenolytic proterty ); 5 times potent than and less toxic than PGF 2 α ; costly Dinoprost tromethammine (PGF 2 α ): 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 PGE 1 : 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 : PGE 1 ) 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-HT 2 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

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