45) OXYTOCIN

[Editor]

a) has an antidiuretic effects
b) is synthesized in the posterior pituitary gland
c) stimulates breast milk production
d) is a steroid
e) causes uterine contraction

[Editor]

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Oxytocin is a nonapeptide made in the paraventricular nuclei of the hypothalamus and stored in the posterior pituitary gland. When released it causes smooth muscle contraction around the lactating mammary gland causing milk ejection and myometrial uterine contraction.

oxytocin has direct antidiuretic action (AtoZ).

Because oxytocin possesses slight antidiuretic activity, its prolonged i.v. administration at high doses in conjunction with large volumes of fluid, as may be the case in the treatment of inevitable or missed abortion, or in the management of postpartum haemorrhage, may cause water intoxication associated with hyponatraemia. To avoid this rare complication, the following precautions must be observed whenever high doses of oxytocin are administered over a long time: an electrolyte-containing diluent must be used (not dextrose); the volume of infused fluid should be kept low (by infusing oxytocin at a higher concentration than recommended for the induction or enhancement of labour at term); fluid intake by mouth must be restricted; a fluid balance chart should be kept and serum electrolytes should be measured when electrolyte imbalance is suspected.