Skip to ContentGo to accessibility pageKeyboard shortcuts menu
OpenStax Logo
Pharmacology for Nurses

36.3 Uterine Motility Drugs and Lactation Considerations

Pharmacology for Nurses36.3 Uterine Motility Drugs and Lactation Considerations

Learning Outcomes

By the end of this section, you should be able to:

  • 36.3.1 Identify the characteristics of uterine motility drugs used during pregnancy and labor.
  • 36.3.2 Explain the indications, actions, contraindications, and adverse reactions of uterine motility drugs used during pregnancy and labor.
  • 36.3.3 Describe nursing implications for uterine motility drugs used during pregnancy and labor.
  • 36.3.4 Explain the client education related to uterine motility drugs used during pregnancy and labor.
  • 36.3.5 Briefly discuss maternal and fetal health considerations when using medications during pregnancy, labor, and delivery.
  • 36.3.6 Briefly describe nursing implications and client education regarding medication use while breastfeeding.

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.

Lactation is the secretion of breast milk by the mammary glands. Some medications can pass from breast milk to the infant. Thus, when the lactating client must take medications, consideration must be given to the possible harmful effects on the infant. Because this content is highly specialized and used only in maternal health, this section will cover only basic information.

Uterine Motility Drugs

Uterine motility drugs affect the movement (contractions) of the uterus. Motility drugs may either increase or decrease uterine contractions, depending on the client’s specific situation. Fetal distress, abnormal fetal presentation, fetal demise, and maternal hemorrhage might be reasons to increase uterine contractions and facilitate delivery. On the other hand, premature labor may be a reason to slow uterine contractions. Generally, these medications are administered in an acute-care setting with monitoring equipment available.

Oxytocics

Oxytocics are used to induce and increase uterine contractions during labor. The two drugs in this category are methylergonovine and oxytocin. These drugs are administered in labor and delivery or postpartum units in a medical facility where the client can be monitored closely.

Methylergonovine is administered IM or via IV immediately after delivery and then orally for up to 1 week as needed. 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. The IM dose is 1 mL (0.2 mg) after delivery of the anterior shoulder, after delivery of the placenta, or during the puerperium (several weeks after childbirth). Dosage may be repeated as required at intervals of 2–4 hours. The IV dose is 1 mL (0.2 mg) administered slowly over a period of no less than 60 seconds (DailyMed, Methylergonovine, 2020).

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. Oxytocin works by exerting a selective action on the smooth musculature of the uterus, which stimulates rhythmic contractions of the uterus, increases the frequency of existing contractions, and improves muscle tone of the uterus. It can be used to facilitate labor contractions as well as to prevent postpartum hemorrhage.

Table 36.11 lists common oxytocics with typical routes and dosing for adult clients.

Drug Routes and Dosage Ranges
Methylergonovine
(Methergine)
1 mL (0.2 mg) intramuscularly or intravenously (IV) (IV dose administered slowly over a period of no less than 60 seconds).
Oxytocin
(Pitocin)
Continuous infusion: 1 mL (10 units/mL) combined with 1000 mL of an isotonic diluent such as lactated Ringer’s solution.
Initial dose: No more than 1–2 mU/minute; may be gradually increased in increments of no more than 1–2 mU/minute until normal labor contraction pattern established.
To control postpartum bleeding: 10–40 units added to 1000 mL of a nonhydrating diluent. Rate adjusted as necessary to control uterine atony.
1 mL (10 units) of oxytocin intramuscularly after delivery of placenta.
Table 36.11 Drug Emphasis Table: Oxytocics (source: https://dailymed.nlm.nih.gov/dailymed/)

Adverse Effects and Contraindications

Methylergonovine is contraindicated or used cautiously in clients who have coronary artery disease, diabetes, or hypercholesterolemia because it may increase the risk for more serious side effects. Kidney and liver disease are also conditions that may require caution when using methylergonovine because of delayed metabolism and excretion of the drug. Pregnancy, hypertension, and toxemia are contraindications for the drug. One notable drug–food interaction is grapefruit and grapefruit juice (DailyMed, Methylergonovine, 2020).

Side effects include worsening of cardiovascular disease, diabetes, hypercholesterolemia, abdominal pain, headache, and increased blood pressure. Other less-common side effects include chest pain or discomfort; difficult or labored breathing; dizziness; pounding or irregular heartbeat; pain or discomfort in the arms, jaw, back, or neck; and puffiness around the eyes, face, lips, or tongue (DailyMed, Methylergonovine, 2020).

Oxytocin is contraindicated in hypersensitivity, obstetric emergencies that negatively affect either the birthing parent or fetus, during fetal distress, when vaginal delivery is inadvisable or fetal positions/presentations are not favorable for delivery, and in uterine contraction pattern dysfunction.

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

Table 36.12 is a drug prototype table for oxytocics featuring oxytocin. It lists drug class, mechanism of action, adult dosage, indications, therapeutic effects, drug and food interactions, adverse effects, and contraindications.

Drug Class
Oxytocic

Mechanism of Action
Exerts a selective action on the smooth musculature of the uterus and stimulates rhythmic contractions of the uterus, increases the frequency of existing contractions, and raises the tone of the uterine musculature
Drug Dosage
Continuous infusion: 1 mL (10 units/mL) combined with 1000 mL of an isotonic diluent such as lactated Ringer’s solution.
Initial dose: No more than 1–2 mU/minute; may be gradually increased in increments of no more than 1–2 mU/minute until normal labor contraction pattern established.
To control postpartum bleeding: 10–40 units added to 1000 mL of a nonhydrating diluent. Rate adjusted as necessary to control uterine atony.
1 mL (10 units) of oxytocin intramuscularly after delivery of placenta.
Indications
Initiation or improvement of uterine contraction

Therapeutic Effects
Induces labor and promotes contractions postpartum
Stimulates lactation
Facilitates delivery of fetus in some abortion situations
Drug Interactions
Cyclopropane anesthesia (may modify oxytocin’s cardiovascular effects)

Food Interactions
No significant interactions
Adverse Effects (Birthing Parent)
Nausea
Vomiting
Cardiac dysrhythmias
Uterine hypertonicity
Uterine rupture
Postpartum hemorrhage
Pelvic hematoma
Water intoxication
Dilutional hyponatremia

Adverse Effects (Fetus)
Bradycardia and other cardiac dysrhythmias
Impaired fetal oxygenation
Permanent brain or central nervous system damage
Retinal hemorrhage
Contraindications
Hypersensitivity
Obstetric emergencies that negatively affect either birthing parent or fetus
Fetal positions/presentations that are not favorable for delivery
Fetal distress
When vaginal delivery is inadvisable
Uterine contraction pattern dysfunction
Table 36.12 Drug Prototype Table: Oxytocin (source: https://dailymed.nlm.nih.gov/dailymed/)

Tocolytics

Tocolytics are drugs used to delay contractions to prevent premature labor and the associated risks, including death of the infant. Magnesium sulfate (MgSO4) is the drug used for this purpose. The indications for a tocolytic drug are premature labor after 20 weeks’ gestation and generally prior to the 34th week. 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.

MgSO4 acts as a CNS and muscular depressant by preventing the peripheral neuromuscular transmission of acetylcholine. Also, MgSO4 is a calcium antagonist, thus blocking calcium from entering cells and causing muscle contractions.

As a tocolytic agent, MgSO4 use is controversial. Its primary use is controlling the seizures of preeclampsia or eclampsia in the birthing parent. It can possibly slow uterine contractions long enough to administer corticosteroids to the birthing parent, but current research does not support this belief. MgSO4 is a drug that can cause sudden and severe adverse effects, and the client must be monitored closely. 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. The treatment for magnesium toxicity is intravenous calcium gluconate or calcium chloride.

MgSO4 can also be significantly detrimental to the fetus. It can cause hypocalcemia, skeletal demineralization, osteopenia, and bone and skeletal abnormalities if used more than 5–7 days during fetal development. The infusion during labor can lead to heart rate changes, hypotonia, respiratory depression, and possibly death.

Table 36.13 is a drug prototype table for tocolytics featuring magnesium sulfate. It lists drug class, mechanism of action, adult dosage, indications, therapeutic effects, drug and food interactions, adverse effects, and contraindications.

Drug Class
Tocolytic/antiseizure

Mechanism of Action
Blocks neuromuscular transmission
Calcium antagonist
Drug Dosage
Initial dose: 10–14 g.
Continuous infusion: 4 g in 5% dextrose at a rate generally not to exceed 150 mg/minute, or 7.5 mL of a 2% concentration (or its equivalent) per minute.
Intramuscular: Simultaneously administer 2 injections of 4–5 g (32.5–40.6 mEq) each.
Indications
Maternal seizure activity
Preterm labor

Therapeutic Effects
Prevention and control of seizures in preeclampsia and eclampsia
Slows uterine contractions
Drug Interactions
Aminoglycosides
Amphotericin B
Cyclosporine
Diuretics
Digitalis
Cisplatin
CNS depressants such as barbiturates, narcotics, or other hypnotics (or systemic anesthetics)

Food Interactions
Alcohol
Adverse Effects (Birthing Parent)
Flushing
Sweating
Hypotension
Depressed reflexes
Flaccid paralysis
Hypothermia
Circulatory collapse
Cardiac and central nervous system depression proceeding to respiratory paralysis
Hypocalcemia with signs of tetany
Contraindications
Hypersensitivity
Toxemia of pregnancy during the 2 hours preceding delivery
Myocardial damage
Diabetic coma
Heart block
Hypermagnesemia
Hypercalcemia

Caution:
Use extremely cautiously in myasthenia gravis and other muscular diseases and in clients with renal conditions
Table 36.13 Drug Prototype Table: Magnesium Sulfate (source: https://dailymed.nlm.nih.gov/dailymed/)

Abortifacients

Abortifacients are medications used to evacuate the uterus via powerful contractions. These contractions empty the uterus of implanted trophoblasts, the cells that become the placenta, and prevent any fertilized egg from being implanted. Abortifacients are used during weeks 12–20 to terminate a pregnancy or to expel the fetus in cases of fetal demise. Carboprost and mifepristone are the drugs in this category.

The topic of abortion is highly controversial in the United States. The U.S. Supreme Court overturned the Roe v. Wade precedent in 2022. Thus, each U.S. state now writes and enacts its own legislation regarding abortion. In some states, health care professionals can be criminally charged for various actions related to abortions. Because nurses may be in situations that could involve some aspect of abortion, they should be cognizant of the abortion laws in the state where they practice. Each state’s nurses’ association and board of nursing, as well as the American Nurses Association, are resources nurses can contact for any questions or concerns about abortion laws. (See this American Nurses Association website on Sexual and Reproductive Health for additional resources.)

Table 36.14 lists common abortifacients and typical routes and dosing for adult clients.

Drug Routes and Dosage Ranges
Carboprost
(Hemabate)
Initial dose of 1 mL (250 mcg) deep intramuscular injection with tuberculin syringe.
Subsequent doses of 250 mcg should be administered at 1½–3½ hour intervals depending on uterine response.
Mifepristone
(Mifeprex, Korlym)
Day 1: One 200 mg tablet orally.
Day 2 or 3: 200 mcg misoprostol tablets, total dose 800 mcg, buccal route.
Minimum 24-hour interval between mifepristone and misoprostol doses.
Table 36.14 Drug Emphasis Table: Abortifacients (source: https://dailymed.nlm.nih.gov/dailymed/)

Adverse Effects and Contraindications

Adverse effects of abortifacients include abdominal cramping, heavy bleeding, headache, nausea, vomiting, diarrhea, backache, diaphoresis. Uterine perforation or rupture are also possible side effects.

Contraindications include drug allergy, active pelvic inflammatory disease, and acute cardiac, renal, hepatic, or pulmonary disease. These drugs should also not be used by lactating clients unless an alternative feeding method is possible. Caution should be used if a client has a history of asthma, hypertension, adrenal disease, vaginitis, or uterine scarring.

Table 36.15 is a drug prototype table for abortifacients featuring mifepristone. It lists drug class, mechanism of action, adult dosage, indications, therapeutic effects, drug and food interactions, adverse effects, and contraindications.

Drug Class
Abortifacient

Mechanism of Action
Empties the uterus of implanted trophoblasts, the cells that become the placenta, and prevents any fertilized egg from being implanted
Dose
Day 1: One 200 mg tablet orally.
Day 2 or 3: 200 mcg misoprostol tablets, total dose 800 mcg, buccal route.
Minimum 24-hour interval between mifepristone and misoprostol doses.
Indications
Medical termination of intrauterine pregnancy through 70 days gestation

Therapeutic Effects
Termination of pregnancy
Drug Interactions
Rifampin
Dexamethasone
St. John’s wort
Phenobarbital
Carbamazepine

Food Interactions
Grapefruit and grapefruit juice
Adverse Effects
Abdominal cramping
Heavy bleeding
Headache
Nausea
Vomiting
Diarrhea
Backache
Diaphoresis
Uterine perforation or rupture
Contraindications
Drug allergy
Active pelvic inflammatory disease
Acute cardiac, hepatic, or pulmonary disease
Confirmed or suspected ectopic pregnancy or undiagnosed adnexal mass
Chronic adrenal failure (risk of acute adrenal insufficiency)
Concurrent long-term corticosteroid therapy (risk of acute adrenal insufficiency)
History of allergy to mifepristone, misoprostol, or other prostaglandins
Hemorrhagic disorders or concurrent anticoagulant therapy (risk of heavy bleeding)
Termination of intrauterine pregnancy in clients with an IUD in place
Table 36.15 Drug Prototype Table: Mifepristone (source: https://dailymed.nlm.nih.gov/dailymed/)

Nursing Implications

The nurse should do the following for clients who are taking uterine motility drugs:

  • Assess client’s medical and drug history as appropriate for the setting.
  • Determine drug allergies.
  • Assess client’s labor and delivery status (active, complicated, patterns, cervical dilation, contractions, etc.)
  • Assess client’s mental and neurological status and vital signs, as well as fetal status, and monitor throughout procedure and as indicated.
  • Initiate appropriate maternal and fetal monitoring equipment such as cardiac monitor and fetal heart rate monitor.
  • Assess any contraindications/precautions for the specific medication to be used.
  • Determine age of fetus (for abortifacients).
  • Monitor laboratory values as ordered and indicated.
  • Provide emotional support.
  • Establish seizure precautions as needed.
  • Initiate and maintain intravenous access.
  • Provide client teaching regarding the drug and when to call the health care provider. See below for client teaching guidelines.

Clinical Tip

Administration of Mifepristone

  • Inform the client that uterine bleeding and uterine cramping will occur
  • Advise the client that serious and sometimes fatal infections and bleeding can occur very rarely.
  • Mifepristone tablets, 200 mg, are only available through a restricted program called the Mifepristone REMS (Risk Evaluation and Mitigation Strategy) Program:
    • Clients must sign a Client Agreement Form.
    • Mifepristone tablets are only available by or under the supervision of certified prescribers or by certified pharmacies on prescriptions issued by certified prescribers.
  • Misoprostol must be taken with mifepristone and within the specified time in order for a successful termination of pregnancy.

Client Teaching Guidelines

The client taking a uterine motility drug should:

  • Understand the indications, side effects, and contraindications of the specific drug being used in their situation.
  • Be able to give informed consent to the use of the drugs (if necessary).
  • Report any serious side effects (prolonged severe cramping, heart palpitations, chest pain, difficulty breathing or shortness of breath, muscle weakness).
  • If drug is used at home, take medication as prescribed.
  • Contact the health care provider with any questions or concerns.
  • Go to the nearest hospital emergency department for emergent situations (fever, severe abdominal pain, prolonged heavy bleeding, or syncope) or for abdominal pain or discomfort, general malaise, weakness, nausea, vomiting, or diarrhea occurring more than 24 hours after taking misoprostol.

The client taking a uterine motility drug should not:

  • Stop taking or take a different dose of the medication than prescribed by their health care provider.
  • Clients taking methylergonovine should avoid consuming grapefruit or grapefruit juice.
  • Smoke or drink alcohol.
  • Engage in sexual activity.
  • Exercise or engage in strenuous activity.

FDA Black Box Warning

Mifepristone

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

Drugs During Pregnancy and Lactation

Drug therapy must be approached cautiously during pregnancy, as some medications may have serious effects for the pregnant client or the fetus. Medications can be passed to the fetus through the placental membrane. Some medications are teratogenic, meaning they can cause serious birth defects, especially if given within the first trimester. The most critical period for fetal development is from conception to day 58–60 when major fetal organs form. Although some medications can pose risks of harm to the fetus, some maternal conditions such as pregnancy-induced hypertension or gestational diabetes may also cause harm. The situation must be viewed from a perspective of risks versus benefits to the birthing parent and fetus/infant. The emphasis for medications that treat a maternal condition is on choosing the safest drug from a class and monitoring the client more closely. In this way, the risks can be mitigated, even if not eliminated.

After delivery, special precautions are still needed for clients who are breastfeeding, as some medications can be transferred to the infant through breast milk. The National Library of Medicine (NLM) maintains the LactMed® database of drug information on relevant medications that clients who are breastfeeding may be exposed to (National Library of Medicine, n.d.). 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.

Citation/Attribution

This book may not be used in the training of large language models or otherwise be ingested into large language models or generative AI offerings without OpenStax's permission.

Want to cite, share, or modify this book? This book uses the Creative Commons Attribution License and you must attribute OpenStax.

Attribution information
  • If you are redistributing all or part of this book in a print format, then you must include on every physical page the following attribution:
    Access for free at https://openstax.org/books/pharmacology/pages/1-introduction
  • If you are redistributing all or part of this book in a digital format, then you must include on every digital page view the following attribution:
    Access for free at https://openstax.org/books/pharmacology/pages/1-introduction
Citation information

© May 15, 2024 OpenStax. Textbook content produced by OpenStax is licensed under a Creative Commons Attribution License . The OpenStax name, OpenStax logo, OpenStax book covers, OpenStax CNX name, and OpenStax CNX logo are not subject to the Creative Commons license and may not be reproduced without the prior and express written consent of Rice University.