Randomised, cross-over, placebo controlled trial of magnesium citrate in the treatment of chronic persistent leg cramps

Abstract

Background: Nocturnal leg cramps are common and distressing. The only treatment of proven effectiveness is quinine, but this has a number of side effects. Magnesium salts have been shown to reduce leg cramp distress in pregnancy. This study tests whether magnesium citrate is effective in the treatment of leg cramps in non-pregnant individuals by conducting in a randomised, double-blind, cross-over placebo-controlled trial.

Material/methods: Volunteers suffering regular leg cramps were recruited. Magnesium citrate equivalent to 300 mg magnesium and matching placebo were given for 6 weeks each. The number of cramps recorded in the cramp diary during the final 4 weeks of magnesium and placebo treatment, severity and duration of cramps and the participants' subjective assessment of effectiveness were analysed.

Results: In subjects who started with placebo (n=29) the median (95% CI) number of cramps was 9 (6-17) on placebo and 5 (4-8) on magnesium. For the group starting with magnesium (n=17) the median no of cramps was 9 (5-13) on magnesium and 8 (4-14) on placebo. There was no significant carry-over effect (p=0.88), but a highly significant period effect (p=0.008). There was a trend towards less cramps on magnesium (p=0.07). There was no difference in cramp severity and duration between the groups. Significantly more subjects thought that the treatment had helped after magnesium than after placebo 36 (78%) and 25 (54%) respectively, (p=0.03). Diarrhoea was recorded as a side effect of magnesium.

Conclusions: The results suggest that magnesium may be effective in treatment of nocturnal leg cramps. Further evaluation is recommended.