Oral versus intravenous magnesium supplementation in patients with magnesium deficiency.

The efficacy of oral magnesium supplementation in correcting magnesium deficiency was examined in a group of 40 elderly patients with suspected magnesium deficiency. The patients were randomized in a double-blind, placebo-controlled fashion to oral magnesium-lactate-citrate for 6 weeks. Magnesium status was assessed by an intravenous magnesium-loading test at baseline and after treatment. For comparison, another group of 23 patients received 30 mmol magnesium sulfate intravenously daily for 7 days. A group of 30 patients without known predisposition to magnesium deficiency and a group of 27 young healthy subjects served as controls. The initial magnesium-loading test in the placebo group reduced magnesium retention from a mean 41% (95% confidence intervals 34-49) to 22% (15-29) (p less than 0.01). In the group receiving oral magnesium supplementation for 6 weeks, magnesium retention decreased from 39% (31-47) to 10% (2-18) (p less than 0.01), which was significantly better than with placebo treatment (p less than 0.01). The magnesium retention after oral magnesium supplementation was comparable to that observed after parenteral administration of magnesium for 7 days, 6% (-4 to 16), and to that in the reference groups of patients 4% (-2 to 10) and healthy control subjects 3% (-2 to 8). The study suggests that the bioavailability of orally given magnesium-lactate-citrate is satisfactory, and that oral administration of magnesium for 6 weeks may restore magnesium depots in patients with magnesium deficiency.