Magnesium sulfate (or sulphate, sulfate) is a chemical compound containing magnesium and sulfate, with the formula MgSO4. It is often encountered as the heptahydrate, MgSO4.7H2O, commonly called Epsom salts.
Magnesium is essential for the formation of strong bones and healthy teeth, the transmission of nerve signals and the contraction of muscles. It activates several enzymes and is important in the conversion of blood sugar into energy. It also helps regulate the body's temperature.
Magnesium occurs naturally in green, leafy vegetables, nuts wholemeal cereals, soya beans and seafoods. Drinking water in hard water areas is also a source of magnesium.
Supplements are only necessary for magnesium deficiency associated with impairment of absorption from the intestines such as repeated vomiting or diarrhoea, advanced kidney disease, severe alcoholism or prolonged treatment with certain diuretic medicines.
It is also to treat abnormal heart rhythms, especially in situations when the levels of potassium are low. In this situation, the levels of magnesium are often also low. Adding magnesium can correct the abnormal heart rhythms by resetting the normal electrical activity in the heart.
Magnesium sulphate may be given for the treatment of high blood pressure and fits (convulsions) in the later stages of pregnancy (eclampsia). It reduces the electrical excitability of the brain and thereby reduces the chance of fitting.
How can this medicine affect other medicines?
Magnesium sulphate may cause a reduction in blood pressure when taken together with calcium channel blockers such as nifedipine.
There may be an increase in the effects of neuromuscular blocking agents when given together with magnesium sulphate.
When magnesium sulphate is given together with the following medicines there may be a risk of respiratory depression: high dose barbiturates, opioids, sleeping medicines, aminoglycoside antibiotics.
Magnesium sulphate should be administered with caution to patients receiving digoxin.
Some muscle relaxants may have their effect increased when used at the same time as magnesium.
The changing role of magnesium sulphate therapy
Magnesium sulphate is not an effective tocolytic. Magnesium sulphate therapy was also linked to preterm neonatal deaths in one study, which was stopped before completion. Other studies suggest a possible neuroprotective effect of magnesium. Both of these issues require further study. Magnesium sulphate is clearly the drug of choice to prevent recurrent eclampsia and to treat severe pre-eclampsia.
Authored by Breen TW, Yang T
Is serum magnesium estimate necessary in patients with eclampsia on magnesium sulphate?
The therapeutic index of magnesium is said to be low, hence, there are fears of toxicity when used as anticonvulsant in eclamptic patients. The objective of this study was to determine the serum levels of magnesium in eclamptic patients treated with magnesium sulphate and relate the levels with clinical indicators. It was a prospective study involving consecutive eclamptic patients that were managed between January and December 2002, with magnesium sulphate as the sole anticonvulsant agent, using a modified Pritchard regimen. Blood samples were taken before the administration of the loading and maintenance doses of magnesium sulphate and serum levels of magnesium were estimated using the Jenway 605 colorimeter. There were 19 patients and 72 blood samples. The mean baseline serum magnesium was 0.72 +/- 0.10 mmol/L while serum magnesium levels when the patients were on treatment ranged from 1.95 to 2.82 mmol/L. No serum magnesium level was greater than 3.0 mmol/L and none of the patients had clinical evidence of magnesium toxicity. We conclude that serum magnesium levels in these patients were within the therapeutic range, therefore, routine estimation of this cation is not necessary. Even where the laboratory facility is available, it is suggested that serum estimation be limited to cases where clinical monitors suggest toxicity.
Authored by Ekele BA, Badung SL.
Effects of magnesium sulphate and clonidine on propofol consumption, haemodynamics and postoperative recovery
BACKGROUND: This placebo-controlled, double-blind study was designed to assess the effects of magnesium sulphate and clonidine on peroperative haemodynamics, propofol consumption and postoperative recovery. METHODS: Sixty ASA I-II patients undergoing spinal surgery were randomized into three groups. Group M received magnesium sulphate 30 mg kg(-1) as a bolus before induction and 10 mg kg(-1) h(-1) by infusion. Group CL received clonidine 3 microg kg(-1) as a bolus before induction and 2 microg kg(-1) h(-1) by infusion during the operation period. The same volume of isotonic solution was administered to the control group (group CT). Anaesthesia was induced with propofol and was maintained with propofol infusion [dose according to the bispectral index (BIS), fentanyl and cisatracurium. Analysis of variance and the Bonferroni test were used for statistical analysis. RESULTS: Induction of anaesthesia with propofol was rapid in the presence of magnesium sulphate and clonidine. The time for BIS to reach 60 was significantly shorter in group M and group CL(P<0.0001) but postoperative recovery was slower with magnesium sulphate compared with the clonidine and control groups (P<0.0001). There was no statistical difference in heart rate and arterial blood pressure between the groups. Propofol requirements for induction and maintenance of anaesthesia were significantly lower with magnesium and clonidine (P<0.0001). CONCLUSION: Clonidine caused bradycardia and hypotension and magnesium sulphate caused delayed recovery, but can be used as adjuvant agents with careful management.
Authored by Altan A, Turgut N, Yildiz F, Turkmen A, Ustun H.