Oxytocin (Oxt) is a hormone, neuropeptide, and medication. As a medication, it is used to cause contraction of the uterus in order to start labor or increase the speed of labor, and to stop bleeding following delivery. For this purpose, it is given either by injection into a muscle or into a vein.

The use of oxytocin as a medication can result in excessive contraction of the uterus that can cause distress in an unborn baby. Common side effects in the mother include nausea and a slow heart rate. Serious side effects include water intoxication with an excessive dose and uterus rupture. Allergic reactions may also occur.

Oxytocin is normally produced by the paraventricular nucleus of the hypothalamus and released by the posterior pituitary. It plays a role in social bonding, sexual reproduction in both sexes, and during and after childbirth. Oxytocin is released into the bloodstream as a hormone in response to stretching of the cervix and uterus during labor and with stimulation of the nipples from breastfeeding. This helps with birth, bonding with the baby, and milk production.

See also hormone