From the FDA Drug Label
CONTRAINDICATIONS Pyridostigmine bromide is contraindicated in mechanical intestinal or urinary obstruction, and particular caution should be used in its administration to patients with bronchial asthma. The FDA drug label does not answer the question.
From the Research
Magnesium sulfate is contraindicated in this patient with myasthenia gravis. This patient presents with preeclampsia with severe features (severe hypertension and visual disturbances) at 37 weeks gestation, requiring induction of labor. While magnesium sulfate would typically be administered for seizure prophylaxis in preeclampsia with severe features, it should not be given to patients with myasthenia gravis. Magnesium sulfate works by blocking calcium channels at the neuromuscular junction, which can exacerbate muscle weakness in myasthenia gravis patients who already have impaired neuromuscular transmission due to acetylcholine receptor antibodies, as noted in a study on drugs that may trigger or exacerbate myasthenia gravis 1. This could potentially lead to respiratory compromise or myasthenic crisis, as seen in a case report of a patient with myasthenia gravis who developed acute respiratory failure after receiving intravenous magnesium sulfate 2. For seizure prophylaxis in this patient, alternative medications such as phenytoin or labetalol would be more appropriate. The patient should continue her pyridostigmine during labor to manage her myasthenia gravis, and intravenous penicillin should be administered for GBS prophylaxis given her positive screening. It is also important to be aware of potential cardiopulmonary drug-drug interactions when administering medications to patients with myasthenia gravis, as noted in a study on intrapartum magnesium sulfate and potential drug-drug interactions 3.