36.3: Uterine Motility Drugs and Lactation Considerations

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.

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.

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.

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.

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.

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.

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.