In which condition is magnesium sulfate contraindicated?

Magnesium sulfate is contraindicated in myasthenia gravis due to the potential for exacerbating muscle weakness. Myasthenia gravis is an autoimmune disorder that leads to varying degrees of muscle weakness due to impaired neuromuscular transmission. The administration of magnesium sulfate can further impair the release of acetylcholine at the neuromuscular junction, leading to an exacerbation of the symptoms associated with myasthenia gravis, which can be particularly concerning in the setting of labor and delivery, where muscle strength is critical.

In contrast, magnesium sulfate can be used cautiously in severe asthma, gestational diabetes, and hypotensive disorders, as it serves various therapeutic roles such as tocolysis and neuroprotection for the fetus. The use in these conditions is generally considered safe under medical supervision, unlike in myasthenia gravis, where the risks outweigh the benefits.