36.3: Uterine Motility Drugs and Lactation Considerations
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. |
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 |
Tocolytics
Tocolytics are drugs used to delay contractions to prevent premature labor and the associated risks, including death of the infant. Magnesium sulfate (MgSO 4 ) 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.
MgSO 4 acts as a CNS and muscular depressant by preventing the peripheral neuromuscular transmission of acetylcholine. Also, MgSO 4 is a calcium antagonist, thus blocking calcium from entering cells and causing muscle contractions.
As a tocolytic agent, MgSO 4 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. MgSO 4 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.
MgSO 4 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 |
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. |
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 |
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.