Tocolytics: Nursing pharmacology

Definitions & Key takeaways

Tocolytics are medications used to inhibit preterm labor or stop contractions in women who are at risk of giving birth prematurely. Tocolytics work by relaxing the uterine muscles, thus delaying the delivery and allowing more time for the fetus to mature and complete pre-delivery medications. Common tocolytic medications include: Magnesium sulfate: It works by reducing the amount of calcium in the uterine muscles, which results in relaxation and decreased contractions. Nifedipine: It works by blocking the calcium channels in the uterine muscle cells, preventing them from contracting. Indomethacin: It works by inhibiting the production of prostaglandins, which normally induce contractions. Terbutaline: A beta-agonist that works by stimulating the beta receptors in the uterus, which results in relaxation and decreased contractions. Patients who are receiving tocolytics should be under close monitoring in health care institutions since severe adverse drug effects can happen and labor can still continue despite treatment.

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Introduction0:00–0:48

Tocolytics are a group of medications that suppress uterine contractions. For that reason, tocolytics are typically used to prolong pregnancy and delay birth after preterm labor starts before 34 weeks of gestation.
Delaying labor is usually done to transfer the client to a higher health care facility if needed, or to administer medications that improve fetal outcomes, such as corticosteroids, which promote fetal lung maturation.Now, the most commonly used tocolytics are magnesium sulfate, calcium channel blockers like nifedipine, beta2-agonists like terbutaline, and NSAIDs like indomethacin.When tocolytics are administered, they cause smooth muscle relaxation in the uterus via various mechanisms.

Mechanism of action0:48–1:52

Both magnesium sulfate and calcium channel blockers like nifedipine block calcium channels, which inhibits the entry of calcium ions into uterine smooth muscles and thus decreases their contractility.
In addition to its tocolytic effect, magnesium sulfate also has a neuroprotective effect on the preterm brain, which is more susceptible to injury.
On the other hand, beta2-agonists bind to beta2-receptors located on the surface of smooth muscle cells, ultimately leading to a decrease in the level of intracellular calcium and decreasing their contractility.
Finally, NSAIDs inhibit the enzyme cyclooxygenase, which normally helps to produce prostaglandins. As a result, there’s a decrease in prostaglandin levels, which ultimately results in relaxation of the uterine smooth muscle.Now, tocolytics can cause several maternal and fetal side effects.

Side effects1:52–4:42

Side effects of magnesium sulfate include nausea, flushing, and headache. In addition, magnesium sulfate toxicity can lead to respiratory depression, cardiac arrest, as well as neurological side effects like altered mental status, reduced deep tendon reflexes, and muscle weakness.
Now, magnesium sulfate may have side effects on the fetus. As it relaxes the muscles, some babies who are exposed to magnesium can present with hypotonia or low muscle tone.
Fortunately, this side effect is not permanent, and usually improves as magnesium sulfate clears from the baby.On the other hand, calcium channel blockers can cause vascular smooth muscle relaxation, which may result in headache, dizziness, flushing, nausea and hypotension, which could decrease blood flow to the fetus.
The good news is that calcium channel blockers don’t seem to cause side effects on the fetus.For beta2-agonists, side effects result from the excessive stimulation of beta2-receptors elsewhere in the body.
In the heart, beta2-agonists can cause tachycardia, arrhythmias, and palpitations, whereas in vascular smooth muscles, they can lead to hypotension.
Other side effects include tremors, nervousness, hyperglycemia, hypokalemia, and the development of pulmonary edema. In addition, beta2-agonists can cross the placenta to the fetus, so another side effect is fetal tachycardia.
Terbutaline should not be administered if the client has known cardiac disease or poorly controlled diabetes mellitus.Finally, side effects of NSAIDs can result from the decreased levels of prostaglandins, making the gastric mucosa more susceptible to injury by gastric acid, which can lead to gastritis and gastroesophageal reflux.
Now, in regard to the fetus, NSAIDs can affect the fetal kidneys, and that decreases the fetal production of urine, which is the main component of the amniotic fluid that surrounds and cushions the fetus.
This ultimately results in oligohydramnios, or low amniotic fluid. NSAIDs can also cause a premature closure of the ductus arteriosus, which is a small vessel that normally connects the fetal aorta to the pulmonary artery.
This allows redirection of blood coming from the heart away from the non-functioning fetal lungs. Premature closure of the ductus arteriosus causes the blood to go directly to the fetal lungs, overwhelming them and resulting in pulmonary hypertension and heart failure.Now, tocolytics are generally contraindicated if pregnancy continuation poses a risk on the client’s life, as in severe preeclampsia, eclampsia, intrauterine infection, and active vaginal bleeding.
Tocolytics are also contraindicated before the 20th week and after the 34th week of gestation, as well as in clients with premature rupture of the membranes.

Contraindications and cautions4:42–6:30

Finally, fetal contraindications to tocolytics include abnormal fetal heart rate pattern, a lethal fetal anomaly like anencephaly, or intrauterine fetal death.
In addition, there are also specific contraindications for each tocolytic medication. For example, magnesium sulfate is contraindicated in clients with myasthenia gravis, since it can aggravate muscle weakness and increase the risk of respiratory muscle paralysis, thus leading to respiratory insufficiency.
Magnesium sulfate should also be used with caution in clients with recent myocardial infarction or those with renal disease, as it is excreted by the kidneys.
On the other hand, calcium channel blockers are contraindicated in clients who have hypotension. Next, beta2-agonists should be avoided in clients who have cardiac disease or uncontrolled diabetes.
Finally, NSAIDs are contraindicated in clients with peptic ulcer disease, impaired renal function, and bleeding disorders.
NSAIDs are also contraindicated after 32 weeks of gestation, when the risk of premature closure of ductus arteriosus is higher.Okay, prior to administering a tocolytic, ensure your client understands the medication is being administered to help delay labor, that there are potential side effects and that you will be monitoring closely while the client receives the medication.
Then, perform a baseline assessment, including vital signs; SpO2; heart and lung sounds; uterine activity; cervical dilation and effacement; and the fetal heart rate, or FHR, and variability; and continue these assessments while your client is receiving the tocolytic.

Nursing considerations & client education6:30–11:45

Lastly, be prepared to institute intrauterine resuscitation measures to increase fetal oxygenation by administering an IV fluid bolus, assisting the client into a lateral position, and administering oxygen at 8-10 L/min through a nonrebreather face mask.Now, each tocolytic you administer has special nursing considerations.
Before you administer magnesium sulfate, obtain a baseline serum creatinine to determine the client’s renal function and insert an indwelling urinary catheter for accurate measurement of urinary output.
Also assess the client’s deep tendon reflexes, or DTRs; and be sure to have a vial of the antidote calcium gluconate readily available to use in the event of toxicity.
Because it’s a high-alert medication, you’ll use an infusion pump to administer magnesium sulfate intravenously. Before administration begins, ask a second nurse to check the dose and infusion pump settings, then start a primary line first, with 1000 mL of crystalloid fluid, and then start a second line for the magnesium sulfate.
Using color-coded tags on the bags and lines of both the magnesium sulfate and the maintenance fluid to provide another layer of safety.
You’ll administer a loading dose first, so it infuses, stay at the bedside and monitor your client closely for adverse reactions.
Then, after the loading dose is complete, begin infusing the maintenance dose, as ordered. During administration, continue your assessments, including any significant changes in the client’s baseline that could indicate toxicity or the development of pulmonary edema, such as respirations less than 12 breaths per minute or more than 24 breaths per minute; SpO2 less than 95%; shortness of breath or adventitious breath sounds; tachycardia or bradycardia; absent DTRs; decreased level of consciousness; urine output less than 30 mL per hour; serum magnesium greater than the therapeutic range of 4-8 mg/dL; or the development of either an indeterminate or abnormal FHR.
If you assess any of these signs or symptoms, stop the infusion; then administer the calcium gluconate per protocol, and notify the obstetrician or midwife immediately.
Alright, if your client is prescribed the calcium channel blocker nifedipine, you will administer the medication orally.
While your client is receiving the medication, continue your assessments and closely monitor for side effects. If you notice a decrease in FHR variability or the presence of decelerations, this may indicate maternal hypotension.
If this occurs, notify the obstetrician or midwife immediately, and institute appropriate intrauterine resuscitation measures, per protocol.
Do not administer nifedipine if your client is hypotensive or hemodynamically unstable.The beta2-agonist terbutaline is most commonly administered subcutaneously, and is only used for up to 72 hours due to the risk of significant side effects.
Before administering and after each dose, be sure to assess the maternal heart rate and the FHR pattern. Then, while the client is receiving terbutaline, closely monitor for side effects; and assess the client’s vital signs; heart and lung sounds; blood glucose levels; uterine activity; and FHR.
Hold the medication and notify the obstetrician or midwife if the FHR is greater than 180 beats per minute or if the FHR patterns are indeterminate or abnormal; if the maternal heart rate is greater than 120 beats per minute; if the client experiences palpitations; or if signs of pulmonary edema are present, like respirations greater than 30 breaths per minute, pulmonary crackles are auscultated, or the SpO2 is less than 95%.Okay, the NSAID indomethacin is administered orally or rectally.
Its use as a tocolytic is limited to 48 hours and is not used after 32 weeks of gestation due to the risk of fetal side effects involving premature closure of the ductus arteriosus.
During administration, continue your assessments and monitor for side effects.Alright, as a quick recap… Tocolytics are a group of medications that suppress uterine contractions.
They’re used in cases of preterm labor to delay labor to allow time to transfer the client to a higher health care facility if needed, or to administer medications like corticosteroids that promote fetal lung development.
The most commonly used tocolytics are magnesium sulfate, which is a high risk medication; nifedipine, which is a calcium channel blocker; terbutaline, which is a beta2-agonist; and indomethacin, an NSAID.
Side effects can vary among different tocolytic medications. Side effects of magnesium sulfate include nausea, flushing, headache, and in severe cases, neurological side effects.
For calcium channel blockers, common side effects are hypotension, headache, and dizziness; while for beta2-agonist, side effects mainly include tachycardia, arrhythmia, and hypotension.

Review11:45–13:32

Finally, NSAIDs can increase the client’s risk of gastritis, and in the fetus, it may result in the premature closure of ductus arteriosus.
Contraindications of tocolytics include gestational age before 20 weeks or after 34 weeks, premature rupture of membranes, abnormal FHR pattern, and client contraindications specific to each type of tocolytic.
There are several important nursing considerations and client education points to consider with tocolytics, such as safe administration, client and fetal assessment, and side effects to report.
blockers. Common side.
Effects are hypotension, headache and dizziness while for beta 2 Agonist side effects, mainly include tachycardia, arrhythmia and hypertension.
Finally, NSAIDs can increase the client's risk of gastritis. And in the fetus.
It may result in the premature closure of ductus arteriosus. Contraindications of tocolytics include gestational age before 20 weeks, or after 34 weeks, premature rupture of membranes abnormal fhr pattern and climb contraindications specific to each type of tocolytic.
There are several important nursing considerations and client education points to consider with tocolytics, such a safe Administration, client and Fetal, assessment, and side effects to report.