Oxytocin

Unit Quantity: 1 vial
Unit Size: 2 mg lyophilized Oxytocin
Purity (HPLC): 98%
Molar mass: 1,025.2 g/mol
Formula: C43H66N12O12S2
 

Oxytocin is a short peptide, just nine amino acids in length, produced in the hypothalamus and released by the posterior pituitary [1]. It is also produced by the placenta, ovaries, and testes. Like many peptide hormones, oxytocin starts out life as a much larger precursor molecule that is subsequently cleaved to create the active hormone. Interestingly, oxytocin has also been found to be produced in the retina, the adrenal glands, and thymus, and the pancreas. Though oxytocin is generally regarded as a neurohypophysial hormone, this thinking is increasingly being thought of as outdated as the potential effects of the peptide increase to include a number of different tissues.

Synthetic oxytocin elicits the same pharmacological response produced by endogenous oxytocin, with cervical dilation, parity, and gestational age as predictors of the dose response to oxytocin administration for labor stimulation. Oxytocin increases the sodium permeability of uterine myofibrils, indirectly stimulating contraction of the uterine smooth muscle. The uterus responds to oxytocin more readily in the presence of high estrogen concentrations and with the increased duration of pregnancy. There is a gradual increase in uterine response to oxytocin for 20 to 30 weeks gestation, followed by a plateau from 34 weeks of gestation until term, when sensitivity increases. Women who are in labor have a greater response to oxytocin compared to women who are not in labor; only very large doses will elicit contractions in early pregnancy. In the term uterus, contractions produced by exogenous oxytocin are similar to those that would occur during spontaneous labor. Oxytocin increases the amplitude and frequency of uterine contractions, which transiently impede uterine blood flow and decrease cervical activity, causing dilation and effacement of the cervix.

Oxytocin causes contraction of the myoepithelial cells surrounding the alveolar ducts of the of the breast. This forces milk from the alveolar channels into the larger sinuses, and thus facilitates milk ejection. While oxytocin possesses no galactopoietic properties, if it is absent the milk-ejection reflex in the breast fails.

Oxytocin causes dilation of vascular smooth muscle, thus increasing renal, coronary, and cerebral blood flow. Blood pressure usually remains unaffected, but with the administration of very large doses or high concentration solutions blood pressure may decrease transiently. This transient decrease in blood pressure leads to reflex tachycardia and an increase in cardiac output; any fall in blood pressure is usually followed by a small, but sustained, increase in blood pressure.

Oxytocin does possess antidiuretic effects, but they are minimal. If oxytocin is administered with an excessive volume of electrolyte-free IV solution and/or at too rapid a rate, the antidiuretic effects are more apparent and water intoxication can result.

Oxytocin appears to have important roles in sexual function and bonding responses in both males and females.

Oxytocin is an essential lactation hormone released during breastfeeding that causes milk ejection and appears to have calming effect on the mother [7]. Administration of exogenous oxytocin to mothers having difficulty in breastfeeding has not been clearly shown to have a beneficial effect on lactation success or in the treatment of breast engorgement. It might be of benefit in women who have lost the neuronal connection between the breast and hypothalamus. Effects on the infant are unlikely when given during breastfeeding.

Numerous studies suggest that oxytocin given during labor can negatively affect breastfeeding, possibly by reducing sucking behavior in the newborn in a dose-dependent manner, or by decreasing postpartum oxytocin release although study methodology and consistency has varied considerably [2, 3, 4, 5, 6, 8]. This effect might be most important during the initiation of breastfeeding, but may not persist after lactation is established[9,10]. One study found that only oxytocin in conjunction with epidural analgesia reduced breastfeeding, but not oxytocin alone [11]. Another study found that all rhythmic reflexes, the antigravity reflex, and total primitive neonatal reflexes were inhibited by intrapartum oxytocin administration, unrelated to dose, which could adversely affect breastfeeding [12]. Some evidence exists that peripartum oxytocin administration might increase the risk of postpartum depression [8].

Store lyophilizate away from heat, moisture and light between 20°C to 25°C. Once reconstituted keep the solution refrigerated between 2°C to 8°C. Keep all medicine out of the reach of children. Throw away any unused vials after expiration date.