Butorphanol tartrate (Stadol) and nalbuphine hydrochloride (Nubain) are the preferred opioid analgesics used during labor because these medications:
are not expensive.
are administered orally.
do not cross the placenta.
do not cause significant respiratory depression in the mother or fetus.
The Correct Answer is D
Choice A rationale
The cost of a medication is a logistical consideration, not a scientific or pharmacological basis for its clinical preference during labor. The selection of an analgesic is primarily determined by its therapeutic profile, including efficacy, safety for both mother and fetus, and its mechanism of action, rather than economic factors.
Choice B rationale
The administration route is a clinical characteristic, but it does not explain why these specific drugs are preferred. Butorphanol and nalbuphine are typically administered intravenously or intramuscularly, not orally, to achieve rapid onset and predictable plasma concentrations, which is crucial for managing acute labor pain.
Choice C rationale
These medications, like most opioids, are lipophilic and have low molecular weights, allowing them to readily cross the placental barrier via passive diffusion. This is a significant aspect of their pharmacology. The preference for these specific drugs lies in their partial agonist/antagonist activity, which mitigates some of the risks of fetal respiratory depression.
Choice D rationale
Butorphanol and nalbuphine are synthetic opioid agonist-antagonists. This unique pharmacological profile means they bind to and activate kappa opioid receptors while acting as antagonists or partial agonists at mu opioid receptors. This dual action provides effective pain relief while concurrently limiting the degree of respiratory depression compared to full mu-opioid agonists, making them a safer choice for both mother and fetus during labor. *.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
Choice A rationale
Normal fetal heart rate variability indicates a healthy, well-oxygenated fetus with a functioning autonomic nervous system. This is a reassuring pattern and would not be the expected outcome of a fentanyl injection, which is known to depress the central nervous system, leading to a decrease in variability.
Choice B rationale
Early decelerations are a benign physiological response caused by head compression during a contraction. They are characterized by a gradual decrease in heart rate that mirrors the contraction and are not associated with uteroplacental insufficiency or the effects of fentanyl.
Choice C rationale
The administration of a narcotic like fentanyl, a central nervous system depressant, can reduce fetal heart rate variability. Loss of variability coupled with late decelerations is a key indicator of uteroplacental insufficiency, which is a concern after some pain medication administrations and requires immediate intervention to improve fetal oxygenation.
Choice D rationale
Variable decelerations are abrupt decreases in the fetal heart rate caused by umbilical cord compression. The shape, depth, and duration of these decelerations are variable, and they are not typically the primary pattern associated with either uteroplacental insufficiency or the direct central nervous system depressant effects of fentanyl.
Correct Answer is D
Explanation
Choice A rationale
Ritodrine is a beta-mimetic tocolytic that can cause maternal and fetal tachycardia. Betamethasone does not reduce this side effect. The primary purpose of betamethasone is to enhance fetal lung maturity. Tachycardia from ritodrine is a known side effect that is managed by monitoring and dosage adjustment, not by administering corticosteroids.
Choice B rationale
The purpose of betamethasone is not to suppress uterine contractions. Betamethasone is a corticosteroid that enhances the production of surfactant in the fetal lungs. Tocolytic medications like nifedipine or magnesium sulfate are used to suppress uterine contractions in preterm labor, allowing time for the betamethasone to take effect.
Choice C rationale
Magnesium sulfate therapy can cause respiratory depression as a side effect. Betamethasone does not maintain maternal respiratory effort or ventilation during this treatment. Calcium gluconate is the antidote for magnesium toxicity. The role of betamethasone is specific to fetal lung maturity, not maternal respiratory support during magnesium sulfate administration.
Choice D rationale
Betamethasone is a corticosteroid that stimulates the production and release of surfactant in the fetal lungs. Surfactant is a substance that reduces surface tension in the alveoli, preventing them from collapsing and improving gas exchange. Administering this medication to the mother improves fetal lung maturity and reduces the risk of respiratory distress syndrome in preterm infants.
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