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Pharmacology · chapter 36 · Reproductive Health Drugs

Uterine Motility Drugs and Lactation Considerations

The 14 things this section of the textbook says that you are most likely to be asked about — quoted word for word, not retold. Then 6 practice questions with the reasoning.

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Key points

  1. Three groups of uterine drugs

    Uterine motility drugs are used during labor to stimulate contractions (oxytocics) or to induce abortion (abortifacients). Other medications (tocolytics), such as terbutaline, are used to delay contraction in the event of premature labor.

  2. Methylergonovine prevents hemorrhage

    Methylergonovine works directly on the uterine smooth muscle to prevent postpartum hemorrhage. It also helps with uterine involution, the process whereby the uterus gradually resumes its prepartum size and weight.

  3. How oxytocin is started

    Oxytocin is administered by intravenous infusion starting at 1–2 mU/minute and gradually increased in increments of no more than 1–2 mU/minute until a normal labor contraction pattern is established.

  4. Methylergonovine contraindications

    Pregnancy, hypertension, and toxemia are contraindications for the drug. One notable drug–food interaction is grapefruit and grapefruit juice (DailyMed, Methylergonovine, 2020).

  5. Methylergonovine side effects

    Side effects include worsening of cardiovascular disease, diabetes, hypercholesterolemia, abdominal pain, headache, and increased blood pressure.

  6. Maternal risks of oxytocin

    The maternal side effects of oxytocin include nausea, vomiting, cardiac dysrhythmias, uterine hypertonicity, uterine rupture, postpartum hemorrhage, pelvic hematoma, water intoxication, and dilutional hyponatremia.

  7. Fetal risks of oxytocin

    Side effects for the fetus include bradycardia and other cardiac dysrhythmias, impaired fetal oxygenation, permanent brain or central nervous system (CNS) damage, and retinal hemorrhage.

  8. Why delay preterm labor

    The purpose of using a tocolytic is to delay labor long enough (24 hours–7 days) to administer corticosteroids to the birthing parent. This allows for fetal lung development to progress to a point where the fetus has enough surfactant to prevent respiratory distress after delivery.

  9. Main use of magnesium sulfate

    Its primary use is controlling the seizures of preeclampsia or eclampsia in the birthing parent.

  10. Signs of magnesium toxicity

    Any change in mental status such as decreased level of consciousness or confusion, sudden drop in blood pressure, loss of patellar reflex, depressed respirations, or hypermagnesemia should be treated immediately to prevent complete cardiovascular collapse and death.

  11. Antidote for magnesium toxicity

    The treatment for magnesium toxicity is intravenous calcium gluconate or calcium chloride.

  12. Mifepristone boxed warning

    Mifepristone can significantly increase the risk of death due to sepsis.

  13. Critical period for fetal development

    The most critical period for fetal development is from conception to day 58–60 when major fetal organs form.

  14. Ask before any drug while breastfeeding

    When assessing clients, nurses should determine if clients are breastfeeding and review the clients’ medications for any potential concerns. Nurses should instruct clients to contact their health care provider first before taking any medication while breastfeeding to reduce the risk of adverse effects on the infant.

Terms to know

Lactation
Lactation is the secretion of breast milk by the mammary glands.
Oxytocics
Oxytocics Oxytocics are used to induce and increase uterine contractions during labor.
Tocolytics
Tocolytics Tocolytics are drugs used to delay contractions to prevent premature labor and the associated risks, including death of the infant.
Teratogenic
Some medications are teratogenic, meaning they can cause serious birth defects, especially if given within the first trimester.
Uterine involution
It also helps with uterine involution, the process whereby the uterus gradually resumes its prepartum size and weight.

Practice questions

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  1. A client receiving IV magnesium sulfate for preeclampsia is newly confused, has respirations of 10 per minute, and her patellar reflexes are absent. Which drug should the nurse have ready?

    1. Terbutaline
    2. Oxytocin
    3. Methylergonovine
    4. Calcium gluconate

    Answer: Calcium gluconate

    Confusion, depressed respirations and loss of patellar reflex are signs of magnesium toxicity, which is treated with IV calcium gluconate or calcium chloride. The other drugs affect uterine contractions and do not reverse magnesium.

  2. A nurse is monitoring a client receiving magnesium sulfate. Which findings require immediate action? Select all that apply.

    1. Decreased level of consciousness
    2. Mild warmth and flushing that resolves
    3. Depressed respirations
    4. Sudden drop in blood pressure
    5. Loss of patellar reflex

    Answer: Decreased level of consciousness, Depressed respirations, Sudden drop in blood pressure, Loss of patellar reflex

    Changes in mental status, a sudden drop in blood pressure, loss of patellar reflex, depressed respirations or hypermagnesemia must be treated immediately to prevent cardiovascular collapse. Flushing is a listed adverse effect but is not among the findings that demand immediate treatment.

  3. A postpartum client has an order for methylergonovine. Her blood pressure is 162/104 mm Hg. What should the nurse do?

    1. Give double the dose to prevent hemorrhage.
    2. Give the dose with grapefruit juice.
    3. Give the dose; it will lower her blood pressure.
    4. Hold the dose and contact the health care provider.

    Answer: Hold the dose and contact the health care provider.

    Hypertension is a contraindication to methylergonovine, and the drug can increase blood pressure. Grapefruit is a drug-food interaction to avoid, and changing the dose is not supported.

  4. A client in labor is receiving an oxytocin infusion. Which maternal adverse effects should the nurse monitor for? Select all that apply.

    1. Dilutional hyponatremia
    2. Water intoxication
    3. Uterine hypertonicity
    4. Hypermagnesemia
    5. Uterine rupture

    Answer: Dilutional hyponatremia, Water intoxication, Uterine hypertonicity, Uterine rupture

    Maternal side effects of oxytocin include uterine hypertonicity, uterine rupture, postpartum hemorrhage, water intoxication and dilutional hyponatremia. Hypermagnesemia is a risk of magnesium sulfate, not oxytocin.

  5. A client in preterm labor at 30 weeks asks why the team wants to slow her contractions for a few days. What is the nurse's best explanation?

    1. To let the baby turn to a head-down position
    2. To allow the cervix to close completely
    3. To avoid the need for any monitoring
    4. To give corticosteroids time to help the baby's lungs mature

    Answer: To give corticosteroids time to help the baby's lungs mature

    Tocolytics delay labor long enough to give the birthing parent corticosteroids so the fetus has enough surfactant to prevent respiratory distress. The other reasons are not given in the section.

  6. A breastfeeding client asks if she can take an over-the-counter cold medicine. What should the nurse advise?

    1. Stop breastfeeding permanently if you need medicine.
    2. Take half the usual dose.
    3. Any over-the-counter product is safe while breastfeeding.
    4. Contact your health care provider before taking any medication while breastfeeding.

    Answer: Contact your health care provider before taking any medication while breastfeeding.

    Some medications pass into breast milk, so clients are taught to contact their provider before taking any medication while breastfeeding. The other answers are not supported by the section.

Where every quote comes from

Section 36.3 Uterine Motility Drugs and Lactation Considerations of Pharmacology for Nurses by Tina Barbour-Taylor, Leah Mueller (Sabato), Donna Paris, Dorie Weaver, OpenStax, 2024. Read the whole section free at openstax.org.

The textbook is licensed under CC BY-NC-SA 4.0. This page quotes it word for word and adds the headings, the order and the practice questions; references to the book's figures and stray spaces left by its formatting are removed. The page is shared under the same licence. Nothing here is sold.