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  1. OXYTOCIN Dr.Dhanalakshmy DNB (O&G)
  2. “OXYTOCICS are the drugs of varying chemical nature that have the power to excite contraction of the uterine muscles.” OXYTOCICS OXYTOCIN ERGOT DERIVATIVES PROSTAGLANDINS Ergometrine & Methergin E2&F2ά PGE2 & PGF2ά
  3. Oxytocin: physiology Human hypothalamus
  4. PREPARATIONS  Synthetic Oxytocin (Ptocin) 5 IU/ ml amp  Syntometrine 5 U Oxytocin + 0.5 mg Ergometrine  Desaminooxytocin buccal tablets 50 IU  Oxytocin nasal spray 40 IU/ ml
  5. UTERUS  Oxitocin is the primary mediator of myometrial contractility during labor.  During the second half of pregnancy, uterine smooth muscle shows an increase in the expression of oxytocin receptors(100-200fold) and becomes increasingly sensitive to the stimulant action of endogenous oxytocin.  Stimulates PG synthesis.  Physiological uterine contraction - fundal contraction; cervical relaxation. (law of polarity maintained)  Cervical and vaginal dilatation results in an acute release of oxytocin from the posterior pituitary in a process known as the Ferguson reflex.
  6. During lactation… oxytocin mechanoreceptors in the nipple/ areola hypothalamic neuronal activity MILK EJECTION Suckling STIMULUS RESPONSE
  7. CVS  In small doses Oxytocin produces vasodialation by direct relaxation of the vascular smooth muscles  Transient hypotension & flushing followed by tachycardia are observed
  8. KIDNEY  In high concentration Oxytocin has weak antidiuretic & pressor activity due to activation of vasopressin receptors
  9. ABSORPTION, METABOLISM, AND EXCRETION  Intravenously (controlled infusion) for initiation and augmentation of labor.  intramuscularly -control of postpartum bleeding.  Buccal & nasal spray- Limited use.  Oxytocin is not bound to plasma proteins and is eliminated by the kidneys and liver.  Circulating half-life of max. 5 minutes. (avg 3-4min) as plasma, utrine & placenta of pregnant women contain enzyme oxytocinase  Circulating half life is 10 to 15 mins in non pregnant women
  10. ADMINISTRATION  IV controlled infusion for initiation & augmentation of labour , abortions  IM for Post partum haemorrage  Buccal , Nasal spray for lactation
  11. Toxicity excessive uterine stimulation Hypertonia (↑duration) uterine rupture. Polysystole (>6 in 10min) placental abruption  “serious toxicity is rare” when oxytocin is used judiciously. fetal distress S T I M U L A T I O N HYPER Grand multipara, Malpresentation Contracted pelvis Prior uterine scar (hyterotomy) NOTE: These complications can be detected early by means of standard fetal monitoring equipment.
  12. Pul. Edema Heart Failure water Intoxication- hyponatremia Antidiuresis excessive fluid retention activation of vasopressin receptors- Seizures & death Inadvertent activation of vasopressin receptors- 30-40mIU/min 40-50IU/min
  13. To avoid hypotension, oxytocin is administered intravenously as dilute solutions at a controlled rate. OXYTOCIN BOLUS HYPOTENSION Transient vasodilation
  14. INDICATIONS THERAPEUTIC PREGNANCY LABOUR PUERPERIUM EARLY LATE -To accelerate Abortion (inevitable, Missed). -Molar preg. -To stop bleeding. -Induction of Abortion. To induce labour. For cervical ripening. Augmentation of labour. Uterine inertia. Active management of 3rd stage To minimise blood loss. Control PPH DIAGNOSTIC Contraction stress test (CST) Oxytocin sensitivity test (OST)
  15. Milk ejection • Intra nasal dose of 40 U , 2 to 5 mins before breast feeding to promote milk ejection
  16. Contraindications PREGNANCY  Grand multipara  malpresentati on  contracted pelvis  cephalopelvi c disproportion  prior uterine scar (hysterotomy ) LABOUR  All cont. in preg. +  Obstructed labour  Incoordinate uterine contraction  FETAL DISTRESS  prematurity ANY TIME  Hypovolemic state  Cardiac disease
  17. For induction of labour  Principle:  Start with LOW DOSE, escalate to achieve optimal response (3contraction in 10min each lasting 45sec)  Maintain the dose- oxytocin titration technique.  OBJECTIVE- Maintain normal pattern of uterine activity till delivery and 30-60min beyond that. NOTE: Start with 4mU/min & ↑every 20min Semi-Fowlers position - avoid venecaval
  18. Calculation of dose delivered in milliunits(mU) & its correlation with drop rate per minute Units of oxytocin mixed in 500ml Ringer solution 1unit=1000 miliunits(mU) Drops per minute (15drops=1ml) 15 30 60 In terms of mU/min 1 2 5 2 4 8 4 8 16 10 20 40 NOTE: In majority of cases, max. response is seen with 16 mU/min i.e 2U in 500ml RL at 60 drops per min
  19. OBSERVATION DURING OXYTOCIN INFUSION  RATE of flow – calculating drops/min  Uterine contraction - Finger tip palpation (hardening)  Intra uterine pressure:-peak 50to60mmHg resting 10to15mmHg  FHR  Assessment of progress of labour - descent of presenting part & dialatation of cervix
  20. Indications for stopping the oxytocin infusion  Nature of uterine contractions-  abnormal uterine contractions occurring frequently (every 2 min or less )  lasting more than 60sec(hyperstimulation)  ↑tonus in between contractions  Fetal distress  Maternal complications  Hyper stimulation is treated with 0.25 mg terbutalin
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