Magnesium sulfate for seizure control in eclampsia
THE CONTEXT
Magnesium sulfate is the drug of choice in the anticonvulsant management of eclampsia. Its effects, intravenous preparation and conditions for repeat dosing are described.
Mechanisms of action
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Magnesium sulfate acts as a membrane stabilizer and neuroprotector.
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It reduces motor endplate sensitivity to acetylcholine and blocks neuronal calcium influx.
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Additional mechanisms include decreased presynaptic glutamate release, blockade of glutamatergic N-methyl-D-aspartate receptors and activation of adenosine action.
Vascular effects and limitations
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Magnesium sulfate induces cerebral vasodilatation, dilates uterine arteries, increases endothelial prostacyclin production and inhibits platelet activation.
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It does not control hypertension.
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The passage reports no detrimental neonatal effects within therapeutic levels and a maternal mortality of 3%.
Intravenous administration and repeat dosing
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For intravenous administration, magnesium sulfate concentration should not exceed 20%. One part of 50% solution is diluted with 1.5 parts of water for injection to produce a 20% solution, which is administered slowly intravenously.
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Repeat injections are given only when knee jerks are present, urine output exceeds 30 mL/hour and the respiratory rate exceeds 12/minute.