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.”
Ergometrine &
Methergin
PGE2 &
PGF2ά
E2&F2ά

3. Oxytocin: physiology
Human hypothalamus

5. PREPARATIONS Synthetic Oxytocin (Ptocin) 5 IU/ ml amp
Syntometrine 5 U Oxytocin mg Ergometrine
Desaminooxytocin buccal tablets 50 IU
Oxytocin nasal spray 40 IU/ ml

6. 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( fold) 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.

7. During lactation… RESPONSE myoepithelial cells Axon terminals contract
STIMULUS
RESPONSE
myoepithelial cells
contract
Axon terminals

8. CVS
In small doses Oxytocin produces vasodialation by direct relaxation of the vascular smooth muscles
Transient hypotension & flushing followed by tachycardia are observed

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

10. 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

11. ADMINISTRATION
IV controlled infusion for initiation & augmentation of labour , abortions
IM for Post partum haemorrage
Buccal , Nasal spray for lactation

12. “serious toxicity is rare” when oxytocin is used judiciously.
HYPER
STIMULATION
fetal distress
Grand multipara,
Malpresentation
Contracted pelvis
Prior uterine scar
(hyterotomy)
NOTE: These complications can be detected
early by means of
standard fetal monitoring equipment.

13. Inadvertent activation of vasopressin receptors-
40-50IU/min
Seizures
& death
30-40mIU/min

14. To avoid hypotension, oxytocin is administered intravenously as
BOLUS
HYPOTENSION
Transient vasodilation
To avoid hypotension, oxytocin is
administered intravenously as
dilute solutions at a controlled rate.

15. INDICATIONS Contraction stress test (CST) DIAGNOSTIC
To minimise
blood loss.
Control PPH
-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
Contraction stress test (CST)
DIAGNOSTIC
Oxytocin sensitivity test (OST)

16. Milk ejection
Intra nasal dose of 40 U , 2 to 5 mins before breast feeding to promote milk ejection

17. Contraindications prematurity 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

18. 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.

19. 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)
In terms of mU/min 1 2 5
NOTE: In majority of cases, max. response is seen with 16 mU/min
i.e 2U in 500ml RL at 60 drops per min

20. 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

21. 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

22. ☻
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