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
PROSTAGLANDINS
Ergometrine &
Methergin E2&F2ά
PGE2 &
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
 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…
oxytocin
mechanoreceptors
in the nipple/ areola
hypothalamic
neuronal activity
MILK EJECTION
Suckling
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 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.

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

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

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)

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

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

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

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

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
☻