Answers

1. A. Oxytocin is considered the drug of choice for inducing labor. All other methods of labor induction are compared to oxytocin to establish their efficacy. Data demonstrate that oxytocin is highly effective in inducing, establishing, and augmenting labor. Oxytocin is not as effective for labor induction when a woman has a cervix that is not favorable for labor. Another agent, such as misoprostol or dinoprostone, may be better for women with unfavorable cervices. Both misoprostol and dinoprostone are prostaglandin analogues. They cause changes in the substance of the cervix and uterine contraction. Although all agents used for labor induction carry the risk of uterine hyperstimulation, prostaglandins are more likely to cause hyperstimulation in women with favorable cervices. Furthermore, the current formulations of prostaglandins do not allow for tight control of blood levels and rapid clearance of medication if hyperstimulation occurs. Methyl ergonovine is an a-agonist that causes direct smooth muscle contraction. Carboprost tromethamine is a methylated analogue of prostaglandin F2a. It is highly potent in causing prolonged uterine contraction. Both medications are used for the control of uterine bleeding after delivery by causing tetanic uterine contractions. These medications are contraindicated for labor induction in women with live fetuses. Both medications can be used in facilitating medical abortions.

2. C. Carboprost tromethamine is methylated at the 15 position. This methylation causes the analogue to be 10 to 15 times more potent then the natural prostaglandin. Smooth muscles that are especially sensitive to prostaglandin F2aare uterine, gastrointestinal, and bronchial. The uterine sensitivity allows for the therapeutic efficacy. The gastrointestinal sensitivity causes the diarrhea and nausea. Prostaglandins are involved in the pyretic response, and thus a side effect of their use may be fever. Oxytocin has antidiuretic hormone qualities, and with prolonged use may cause water intoxication.

3. B. Clinical evidence has shown that the use of this agent has saved many women from surgery by controlling postpartum hemorrhage. It can also induce labor but is not the drug of choice. It will induce rather than inhibit premature labor. A prostaglandin antagonist would be useful to produce closure of the fetal ductus arteriosus.

4. E. Magnesium has no known effect on prostaglandins. The mechanism of action by which magnesium sulfate causes smooth muscle contraction is complex and poorly understood. Magnesium sulfate uncouples excitation-contraction in myome-trial cells through inhibition of cellular action potentials. Furthermore, magnesium sulfate decreases calcium uptake by competing for binding sites, activating adenylate cyclase (reducing intracellular calcium), and stimulating calcium-dependent ATPase, which promotes calcium uptake by sarcoplasmic reticulum.

5. D. Indomethacin is a potent prostaglandin synthesis inhibitor. Patency of the ductus arteriosis depends on the formation of prostaglandins. Closure of the ductus arteriosis can lead to fetal heart failure and death. Also, fetal closure can lead to neonatal pulmonary hypertension. Neonatologists use in-domethacin for the treatment of neonatal patent ductus arteriosis, thus often obviating neonatal heart surgery. Prostaglandin synthesis inhibitors are associated with bleeding. Although bleeding is well documented in children and adults, the use of in-domethacin has not been shown to cause hematuria or gastrointestinal bleeding in the fetus. There is some evidence, however, that maternal use of in-domethacin may increase the risk of neonatal intra-ventricular hemorrhage. Neither muscular paralysis nor cardiac arrest has been demonstrated in the fetus with maternal use of indomethacin.

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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