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
OXYTOCIN
ERGOT
DERIVATIVES
Ergometrine &
Methergin
PROSTAGLANDINS
PGE2 &
E2&F2ά
PGF2ά
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


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

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…
Suckling
mechanoreceptors
in the nipple/ areola
STIMULUS
RESPONSE
MILK EJECTION
oxytocin
hypothalamic
neuronal activity
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

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
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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
 “serious toxicity
judiciously.
is rare” when oxytocin is used
excessive uterine
stimulation
HYPER
S
T
I
M
U
L
A
T
I
O
N
Hypertonia
(↑duration)
uterine rupture.
placental
abruption
Polysystole
(>6 in 10min)
Grand multipara,
Malpresentation
Contracted pelvis
Prior uterine scar
(hyterotomy)
fetal distress
NOTE: These complications can be detected
early by means of
standard fetal monitoring equipment.
Inadvertent activation of vasopressin
receptors- Antidiuresis
40-50IU/min
excessive fluid
retention
activation of
vasopressin
receptorswater
Intoxicationhyponatremia
Pul. Edema
Heart Failure
Seizures
& death
30-40mIU/min
OXYTOCIN
BOLUS
HYPOTENSION
Transient vasodilation
To avoid hypotension, oxytocin is
administered intravenously as
dilute solutions at a controlled rate.
INDICATIONS
THERAPEUTIC
PREGNANCY
EARLY
-To accelerate
Abortion
(inevitable, Missed).
-Molar preg.
-To stop bleeding.
-Induction of
Abortion.
LABOUR
PUERPERIUM
LATE
To induce labour.
For cervical
ripening.
Augmentation of
labour.
To minimise
blood loss.
Uterine inertia.
Control PPH
Active management
of 3rd stage
Contraction stress test (CST)
DIAGNOSTIC
Oxytocin sensitivity test (OST)
Milk ejection
•Intra nasal dose of 40 U , 2 to
5 mins before breast feeding
to promote milk ejection
Contraindications
PREGNANCY

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


Grand
multipara
malpresentati
on
contracted
pelvis
cephalopelvic
disproportion
prior uterine
scar
(hysterotomy)
ANY TIME
LABOUR





All cont. in preg.
+
Obstructed
labour
Incoordinate
uterine
contraction
FETAL
DISTRESS
prematurity

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 minute
Units of oxytocin mixed in
500ml Ringer solution
1unit=1000 miliunits(mU)
1
2
5
Drops per minute
(15drops=1ml)
15
30
In terms of mU/min
2
4
10
4
8
20
60
8
16
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
☻
THA
OU
NK Y