OXYTOCIN

Dr.Dhanalakshmy DNB (O&G)

“OXYTOCICS

are the drugs of varying chemical nature that have the power to excite contraction of the uterine muscles.”

OXYTOCICS

OXYTOCINERGOT

DERIVATIVESPROSTAGLANDINS

Ergometrine & Methergin E2&F2E2&F2άά

PGEPGE2 2 & &

PGFPGF22άά

Oxytocin: physiology

Human hypothalamus

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

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.

During lactation…

oxytocinoxytocin

mechanoreceptors mechanoreceptors in the in the nipple/ areolanipple/ areola

hypothalamic hypothalamic neuronal activityneuronal activityMILK EJECTIONMILK EJECTION

SucklingSuckling

Axon terminals

Axon terminals

myo

epith

elia

l

myo

epith

elia

l

cells

cells

con

trac

t

cont

ract

STIMULUS

RESPONSE

CVS

In small doses Oxytocin produces vasodialation by direct relaxation of the vascular smooth muscles

Transient hypotension & flushing followed by tachycardia are observed

KIDNEY

In high concentration Oxytocin has weak antidiuretic & pressor activity due to activation of vasopressin receptors

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

ADMINISTRATION

IV controlled infusion for initiation & augmentation of labour , abortions

IM for Post partum haemorrage Buccal , Nasal spray for lactation

Toxicity

excessive uterinestimulation

Hypertonia(↑duration)

uterine rupture..

Polysystole(>6 in 10min)

placental abruption

“serious toxicity is rare” when oxytocin is used judiciously.

fetal distress

STIMULATION

HYPER

Grand multipara, MalpresentationContracted pelvisPrior uterine scar(hyterotomy)

NOTE: These complications can be detected NOTE: These complications can be detected

early by means ofearly by means of

standard standard fetal monitoring equipmentfetal monitoring equipment. .

Pul. EdemaPul. EdemaHeart FailureHeart Failure

water water Intoxication-Intoxication-

hyponatremiahyponatremia

AntidiuresisAntidiuresis excessive fluid excessive fluid

retentionretention

activation of activation of vasopressinvasopressin

receptorsreceptors--

Seizures & death

Inadvertent activation of Inadvertent activation of vasopressinvasopressin receptors receptors--

30-40mIU/min

40-50IU/min

To avoid hypotension, oxytocin isadministered intravenously as dilute solutions at a

controlled rate.

OXYTOCIN BOLUS HYPOTENSION

Transient vasodilation

INDICATIONS

THERAPEUTICTHERAPEUTIC

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

DIAGNOSTICContraction stress test (CST)

Oxytocin sensitivity test (OST)

Contraindications

PREGNANCY

Grand multipara

malpresentation

contracted pelvis

cephalopelvic disproportion

prior uterine scar (hysterotomy)

LABOUR

All cont. in preg.

+ Obstructed

labour Incoordinate

uterine contraction

FETAL DISTRESS

prematurity

ANY TIME

Hypovolemic state

Cardiac disease

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

compression.

Calculation of dose delivered in milliunits(mU) & its correlation with drop rate per minuteUnits of oxytocin Units of oxytocin mixed in 500ml mixed in 500ml Ringer solutionRinger solution

1unit=1000 1unit=1000 miliunits(mU)miliunits(mU)

Drops per minuteDrops per minute

(15drops=1ml)(15drops=1ml)

15 30 15 30 60 60

In terms of mU/minIn terms of mU/min

11

22

55

2 4 2 4 8 8

4 8 4 8 16 16

10 20 10 20 40 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

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

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

THANK YOU☻