A 43-year-old primigravida at 37 weeks gestation comes to the labor and delivery department for evaluation of a severe headache that began this morning. The patient now has dark spots in her vision but no epigastric pain, nausea, or vomiting. She also has irregular, nonpainful contractions but no vaginal bleeding or loss of fluid. The patient has myasthenia gravis and takes pyridostigmine; she has no other chronic medical conditions or pregnancy complications. Rectovaginal screening for group B Streptococcus was positive at 35 weeks gestation. Blood pressure is 184/106 mm Hg and pulse is 88/min. The abdomen is soft, gravid, and nontender. The cervix is 3 cm dilated and 50% effaced, and the fetal vertex is at -1 station. Fetal heart rate tracing demonstrates a baseline of 130/min, moderate variability, multiple accelerations, and no decelerations. Tocodynamometry reveals contractions every 8-10 minutes. The patient is admitted for induction of labor due to preeclampsia with severe features. Which of the following medications is contraindicated in this patient?

Question

A 43-year-old primigravida at 37 weeks gestation comes to the labor and delivery department for evaluation of a severe headache that began this morning.  The patient now has dark spots in her vision but no epigastric pain, nausea, or vomiting.  She also has irregular, nonpainful contractions but no vaginal bleeding or loss of fluid.  The patient has myasthenia gravis and takes pyridostigmine; she has no other chronic medical conditions or pregnancy complications.  Rectovaginal screening for group B Streptococcus was positive at 35 weeks gestation.  Blood pressure is 184/106 mm Hg and pulse is 88/min.  The abdomen is soft, gravid, and nontender.  The cervix is 3 cm dilated and 50% effaced, and the fetal vertex is at -1 station.  Fetal heart rate tracing demonstrates a baseline of 130/min, moderate variability, multiple accelerations, and no decelerations.  Tocodynamometry reveals contractions every 8-10 minutes.  The patient is admitted for induction of labor due to preeclampsia with severe features.  Which of the following medications is contraindicated in this patient?

Quizplus · Accepted Answer

11ec25c8_da70_b8de_bc81_29a26f29f9a1_MD0003_00 Myasthenia gravis (MG) is a neuromuscular junction disorder caused by autoantibodies against acetylcholine receptors in skeletal muscle. MG typically does not increase the risk for obstetric complications, and well-controlled disease can remain stable throughout pregnancy (a small subset of women may have a flare in the first trimester or postpartum). Patients may continue to take acetylcholinesterase inhibitors (eg, pyridostigmine) during pregnancy; additional medications may be discontinued based on teratogenicity and disease control during the preconception period. When obstetric complications do occur in patients with MG, management is tailored to avoid disease exacerbation (eg, respiratory muscle weakness). This patient has a commonly seen obstetric complication, preeclampsia with severe features (eg, hypertension, headache, visual changes). In patients without MG, management of preeclampsia with severe features includes magnesium sulfate for seizure prophylaxis. However, in patients with MG, magnesium sulfate is contraindicated because it may trigger a myasthenic crisis (eg, oropharyngeal muscle weakness, respiratory failure requiring intubation) due to inhibition of acetylcholine release at the neuromuscular junction. In these patients, seizure prophylaxis is with valproic acid. (Choice A) Acetaminophen is not contraindicated in pregnancy or in patients with MG and can be used to improve this patient's headache. (Choice B) Antihypertensive therapy is used in pregnant patients with severe hypertension (ie, systolic blood pressure ≥160 mm Hg or diastolic blood pressure ≥110 mm Hg) to decrease the risk of stroke. Although some antihypertensives (eg, beta blockers, calcium channel blockers) can exacerbate muscle weakness in patients with MG, hydralazine does not and is not contraindicated in this patient. (Choice D) Oxytocin is used for labor augmentation and induction. Contraindications to oxytocin include prior classical cesarean delivery (due to the risk of uterine rupture) or fetal heart rate decelerations, which are not seen in this patient. MG is not a contraindication to oxytocin use. (Choice E) Intrapartum penicillin is administered to patients with positive rectovaginal screening for group B Streptococcus to decrease the risk of neonatal transmission. Although some antibiotics (eg, azithromycin, gentamicin) can worsen symptoms of MG, penicillin typically does not and, therefore, is not contraindicated in this patient. Educational objective: Magnesium sulfate, commonly used in obstetrics for seizure prophylaxis (eg, in preeclampsia with severe features), is contraindicated in patients with myasthenia gravis because it may trigger a myasthenic crisis due to the inhibition of acetylcholine release. References: Severe preeclampsia in the setting of myasthenia gravis. (http://www.ncbi.nlm.nih.gov/pubmed/28280642) Myasthenia gravis and preeclampsia: dot all the I's and cross all the T's. (http://www.ncbi.nlm.nih.gov/pubmed/31435279) Myasthenia gravis and pregnancy. (http://www.ncbi.nlm.nih.gov/pubmed/23563874)

A 43-Year-Old Primigravida at 37 Weeks Gestation Comes to the Labor