Dr.Dhanalakshmy DNB (O&G)
are the drugs of varying chemical nature that have the power to excite contraction of the
OXYTOCIN OXYTOCICS ERGOT DERIVATIVES Ergometrine & Methergin PROSTAGLANDINS PGE PGF 2 & ά
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
Oxitocin is the
contractility during labor.
of myometrial 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
mechanoreceptors in the nipple/ areola RESPONSE MILK EJECTION hypothalamic neuronal activity
In small doses Oxytocin produces vasodialation by direct relaxation of the vascular smooth muscles Transient hypotension & flushing followed by tachycardia are observed
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 eliminated by the kidneys and liver
and is Circulating half-life of plasma, utrine & placenta of pregnant women contain enzyme oxytocinase
max. 5 minutes
. (avg 3-4min) as Circulating half life is 10 to 15 mins in non pregnant women
IV controlled infusion for initiation & augmentation of labour , abortions IM for Post partum haemorrage Buccal , Nasal spray for lactation
erious toxicity is rare
” when oxytocin is used judiciously. excessive uterine stimulation
HYPER S T I M U L A T I O N Hypertonia
Polysystole (>6 in 10min) uterine rupture
fetal distress placental abruption Grand multipara, Malpresentation Contracted pelvis Prior uterine scar (hyterotomy)
NOTE: These complications can be detected early by means of standard
fetal monitoring equipment
Inadvertent activation of
Antidiuresis excessive fluid retention Pul. Edema Heart Failure activation of
receptors Seizures & death water Intoxication hyponatremia
To avoid hypotension, oxytocin is administered intravenously as dilute solutions at a controlled rate.
INDICATIONS EARLY PREGNANCY -To accelerate Abortion (inevitable, Missed).
-To stop bleeding.
-Induction of Abortion.
LATE THERAPEUTIC LABOUR To induce labour.
For cervical ripening.
Augmentation of labour.
Active management of 3 rd stage PUERPERIUM To minimise blood loss.
Control PPH DIAGNOSTIC Contraction stress test (CST) Oxytocin sensitivity test (OST)
•Intra nasal dose of 40 U , 2 to 5 mins before breast feeding to promote milk ejection
PREGNANCY Grand multipara malpresentati on 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.
- 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) 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
☻ T H A N K Y O U