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.

Oxytocin is contraindicated or used with caution when vaginal delivery could increase the risk of complications. Common contraindications include the presence of non-reassuring fetal status, in fetal prematurity where the lungs are not fully developed, cephalopelvic disproportion, cervical cancer, active genital herpes infection, unfavorable fetal position, placenta previa, vasa previa, and any other obstetric emergencies that could require surgical intervention.

It should also be avoided in those with grand multiparity, meaning they’ve given birth 5 or more times, and those with uterine prolapse, or at risk of uterine rupture, like clients with 2 or more previous cesarean births.

Finally, it should not be used if the client is receiving a vasopressor like phenylephrine, since both can increase blood pressure.

Now, nurses are responsible for safely administering oxytocin during labor, avoiding excessive stimulation to the uterus or harm to the fetus. So, before starting the infusion, be sure to review the client’s medical record to be sure there are no contraindications to administration.

Assess the cervix to ensure it is ripe, meaning that it has started to change from being firm and thick to soft and thin. Then, confirm that the fetal presentation is favorable for vaginal delivery, and that the estimated fetal gestational age is known.

In addition, assess the fetal status by determining the baseline fetal heart rate or FHR variability, and the presence of accelerations or decelerations.

Finally, teach the client about what to expect as far as contraction strength, duration, and frequency, review measures used to monitor maternal and fetal well-being, and stress the importance of promptly reporting if pain, nausea, or other unpleasant symptoms occur.