DRUGS USED IN UTERINE MOTILITY

1. DRUGS USED IN UTERINE MOTILITY Md. Amran Howlader

2. Drugs action un Uterus - Cause contraction or relaxation of uterus - Uterine contractility enhanced by :  oxytocin  ergometrine (ergonovine)  prostaglandin analogues - Uterine relaxation enhanced by :  B- adrenoceptor agonists  magnesium sulphate  prostaglandin synthetase inhibitors  calcium channel blockers

3. Oxytocin Pharmacological action  - Synthesized in the :  supraoptic nucleus (SON)  paraventricular nucleus (PVN) of hypothalamus - By axonal transport arrive and stored in the posterior pituitary - Sensory stimuli from cervix & vagina induce secretion of oxytocin from posterior pituitary - Stimulation of breast leads to secretion of oxytocin  contraction of myoepithelium  milk ejection reflex

4. On uterus - Stimulates frequency & force of contraction - Effect dependent on presence of estrogen - Contributes to initiation of labor - Sensitivity of uterus to oxytocin increase during pregnancy - Oxytocin induced myometrial contraction inhibited by :  B- adrenoceptor agonists  magnesium sulphate  inhalational anesthetic agents

5. On CVS  - Large amounts   marked transient relaxation of vascular smooth muscle  reduction of blood pressure  flushing  reflex tachycardia

6. Other effects  - Large amounts  antidiuretic effect

7. Mechanism of action:  - Specific receptors in myometrium - Elicits prostaglandin production in endometrial / decidual cells - Alters transmembrane ionic currents in myometrial smooth muscle cells to produce sustained contraction

8.  Pharmacokinetics: - Administration IV to induce labor - Intra-nasal spray – postpartum use to induce lactation - Inactive when administered orally - T ½ 5 – 12 minutes - Metabolized by oxytocinase

9. USES:  - To induce labor or augment dysfunction - Conditions requiring early vaginal delivery  Rh problems  maternal diabetes mellitus - Uterine inertia - Third stage of labor - To control post-partum bleeding - Milk ejection

10. Toxicity:  - When properly used toxicity is rare - Uterine rupture - Water intoxication - Foetal death - Maternal death from hypertensive episodes

11. Contraindications:  - Foetal distress - Prematurity - Abnormal presentation - Cephalo-pelvic disproportion

12. Ergot Alkaloids : Ergometrine • First used as uterine stimulating agent  • Ergot – product of fungus  • Derevative of 6-methy ergoline  • Pure Form – Ergotamine • Ergometrine ( Ergonovine ) water soluble derivative

13. ERGOMETRINE ACTIONS Uterus: - Increase motor activity of uterus Dose related increase in frequency & force of contraction Pregnant uterus is more sensitive Uterus at term is more sensitive than early pregnancy - Combines alpha-agonist , serotonin & other effects

14. Ergometrine Ergonovine is more active and less toxic than ergotamine. Useful for the control of post partum or after labor bleeding. Should never be given before delivery. Given at the time of delivery of placenta.

15. Pharmacokinetics  - Routs of administration : Parentally Orally Rectally - Extensive first-pass effect - T ½ is 2 hours but effect persist for 24 hours - Metabolized in liver - Excreted in bile

16. Side effects - GI upset : diarrhea, nausea, vomiting - Tingling of fingers and toes - Muscle pain - Overdosage  prolonged vasospasm  pallor, anginal pain, gangrene - Contraindicated in : Peripheral vascular disease Coronary heart disease Hypertension Impaired renal & hepatic disease

17. Prostaglandins  Analogues found in uterus are PG-E & PG-F 2-alph Actions : - On Myometrium: > cause strong uterine contraction > sensitivity of uterus to prostaglandins increase as gestation progress - On Cervix : > local instillation of PG induces ripening, softening and relaxation of cervix

18. TOCOLYTIC AGENTS Agents - Agents that inhibit uterine contraction - Used to delay or prevent premature parturition - Slow or arrest delivery for brief periods in order to undertake other therapeutic measures Agents : • B2-adrenoceptor agonist ( Retodrine & Terbutaline ) • Magnesium sulphate • Prostaglandins synthetase inhibitor ( Indomethacin ) • Calcium Channel Blocker ( Nifedepine & Norcardipine)

19. Retodrine • selective B2-adrenoceptor agonist • developed specifically for use as a uterine relaxant • relaxes smooth muscles of : • uterus • bronchial tree • arteries • effective 20-36 weeks gestation

20. Uses  * Mainly used for Rx of premature labor * Rx initiated with IV infusion and about 30 minutes before the end of IV infusion oral therapy begins

21. Adverse effects  * Tachycardia * Increased cardiac output * Fluid overload  maternal pulmonary oedema ( esp. If combined with corticosterioids) *Hyperglycemia *Hypocalcemia

22. Prostaglandin synthetase Inhibitors Cyclooxygenase inhibitors (NSAIDS esp. Indomethacin) inhibit prostaglandin synthesis – can half pre-term labor *Concers of foetal and neonatal side effects limit their use - Premature closure of ductus arteriosis - Increased risk of pulmonary hypertension - Oligo-hydraminios - Post Maturity * Used in gestation prior to 34 weeks

23. Magnesium Sulphate *Effective inhibitor of uterine contraction *Interferes with calcium uptake by myometrial cells which need it to contract *Generally given IV as an infusion

24. Adverse reaction: - GIT – nausea and vomiting - Hot flushes - Blurred vision Toxicity: - Decreased respiratory rate - Hypotension - Extreme muscle Relaxation - Caution *Clost monitoring is required