Oxytocin injection is a sterile aqueous solution of highly purified oxytocic principle derived by synthesis or obtained from the posterior lobe of the pituitary gland of healthy domestic animals used for food by humans. Oxytocin injection contains 20 USP Units of oxytocin and less than 0.4 units of presser activity per mL. Each mL of sterile solution also contains 0.9% w/v sodium chloride, 0.5% w/v chlorobutanol (as a preservative), with water for injection q.s. and pH adjusted to 3.0 to 5.0 with acetic acid.
ACTIONS: Oxytocin acts directly on the smooth musculature of the uterus in all species to induce rhythmic contractions, although in some species the uterine cervix does not respond to oxytocin. The responsiveness of the uterine musculature to oxytocin varies greatly with the stage of the reproductive cycle. During the early phases of pregnancy the uterus is relatively insensitive to the effects of oxytocin, while in the late phases the sensitivity is markedly increased. Most authorities attribute this varying response to the varying levels of estrogen and progesterone during the course of pregnancy.
Oxytocin also has been shown to exert a milk ejecting effect, occasionally referred to as the galactogogic effect. The actual mechanism by which oxytocin stimulates the release of milk from the mammary glands is not known with certainty, but oxytocin is presumed to act on certain smooth muscle elements in the gland.
Oxytocin Injection Indications
Because of the specific action of oxytocin upon the uterine musculature, it is recommended as an aid in the management of the following conditions:
1) To precipitate labor
2) To accelerate normal parturition
3) Postpartum evacuation of uterine debris
4) Postoperative contraction of the uterus following a cesarean section and control of uterine hemorrhage.
Oxytocin will contract the smooth muscle cells of the mammary gland to induce milk let-down if the udder is in a proper physiological state.
CONTRAINDICATION: Do not use in dystocia due to abnormal presentation of the fetus until correction is accomplished.