This is part of an article on the myasthenia.org website that speaks about magnesium and why it is not recommended for patients with neuromuscular junction disorders.


"Magnesium interferes with neuromuscular transmission by inhibiting release of ACh. 58. Magnesium competitively blocks calcium entry at the motor nerve terminal. There may also be a milder postsynaptic affect. Clinically, hypermagnesemia resembles Lambert-Eaton syndrome more so than autoimmune MG. 59 In addition, magnesium can potentiate the action of neuromuscular blocking agents, which has been emphasized in women who had cesarean section after treatment with Mg++ for preeclampsia. 60,61 Patients with underlying junctional disorders are more sensitive to Mg++-induced weakness. Patients with MG. 62,-64 and Lambert-Eaton syndrome. 65,66 have been reported to exacerbate in the setting of Mg++ use in spite of normal or only mildly elevated serum levels. Typically, increased MG symptoms occur with parenteral magnesium administration, but on occasion is seen with oral use. 66 Therefore, parenteral Mg++ administration should be avoided and oral Mg++ preparations used with caution in patients with known junctional disease (myasthenia gravis, Lambert Eaton syndrome, botulism, etc.)."