Oxytocin: Nursing pharmacology

Oxytocin is a peptide hormone released by the posterior pituitary that causes uterine muscle contraction during labor. It’s also responsible for the milk let-down reflex where milk is ejected during breastfeeding.

It’s commonly used to induce labor or help strengthen uterine contractions to facilitate delivery. After delivery of the placenta, it’s used to treat uterine atony, prevent postpartum hemorrhage and to manage incomplete or inevitable spontaneous abortion.

Okay, a synthetic version of oxytocin is used clinically. To induce labor or strengthen contractions, it’s administered via IV.

After reaching the uterus, it will activate receptors on smooth muscle cells and trigger calcium ion release from the sarcoplasmic reticulum.

This increase in intracellular calcium will cause the muscle to contract harder with increased frequency and duration in order to help with the delivery.

When used postpartum, the uterine contractions will squeeze intrauterine vessels to slow or stop postpartum hemorrhage.

Now, when oxytocin is administered as a nasal spray it causes contraction of the myoepithelial cells around milk-containing alveoli in the breasts. This will squeeze the milk into the lactiferous ducts where it could be ejected during lactation.

The main adverse effects of oxytocin are related to uterine hyperstimulation, where there’s too much contraction. This could cause painful contractions, and lead to uterine rupture and hemorrhage. It could even restrict placental blood flow, resulting in abnormal fetal heart rate patterns.

Other side effects include nausea, vomiting, hypertension, cardiac arrhythmias and amniotic fluid embolism. With prolonged use, it could have an effect similar to antidiuretic hormone and increases water retention. This is particularly dangerous since it could cause water toxicity and result in coma or even death.