OXYTOCIN

It is a octapeptide secreted by posterior pituitary along with ADH. It increases the force and frequency of uterine contractions. Increased contractility is due to hightened electrical activity of the myometrial cell membrane-burst discharge are initiated and accentuated. Estrogens sensitize the uterus to oxytocin; nonpregnant uterus and tht during early pregnancy is rather resistant. It also contracts myoepithelium of mammary alveoli and forces milk into the bigger milk sinusoids-milk ejection reflex initiated by suckling. Oxytocin in high does exerts an ADH like action.

Indications

Induction of labour, uterine inertia, Post partum haemorrhage. Cesarean section. Abortion, breast engorgement.

Dosage

Induction or enhancement of labour: i.v. drip infusion of a 5% dextrose soln. containing 1 i.u. oxytocin per 100 ml. 3rd stage labour & puerperium: 5-10 i.u. i.m. or 5 i.u. i.v. slowly. Caesarean secton: 5 i.u. after delivery.

Contra-Indications

Hypertonic contractions, Cephalopelvic disproportion, excessive distention of the uterus as in multiple pregnancy, hydramnious. Hypersensitivity to the drug. Parity greater than4, eldery multiparae, previous caesarean section or other surgery involving the uterus, severe toxaemia, predisposition to amniotic fluid. Placenta praevia.

Special Precautions

Use only medical reasons rather than for convenience. Only under hospital conditions with qualified medical supervision and careful obstetrical monitoring allowing dosage adjustment to individual responses. Use only by i.v. infusion & not by i.m. or s.c.

Side Effects

Injudicious use of oxytocin during laour can produce too strong uterine contractions forcing the presenting part through incompletely dilated birth canal, causing maternal and foetal soft tissue injury, rupture of uterus, foetal asphyxia and death. Water intoxication, toxaemia of pregnancy and renal insufficiency due to ADH like action.

Drug Interactions

Concomitant use with prostaglandins increases risk of uterine rupture & cervical laccerations . Useful combination with ergotamine.