Effect of magnesium therapy on nocturnal leg cramps: a systematic review of randomized controlled trials with meta-analysis using simulations.

BACKGROUND AND
OBJECTIVE: Nocturnal leg cramps (NLC) are common in primary care and may cause severe pain and sleep disturbance. We systematically reviewed the effectiveness of magnesium in treating NLC and the side-effect profile of magnesium compared to placebo.
METHODS: We searched Medline, Embase, Cochrane Library, ClinicalTrials.gov, the International Standard Randomised Controlled Trial Number and the International Clinical Trials Registry Platform registries until August 2012. All randomized controlled trials (RCTs) comparing magnesium therapy for NLC in adults with any other comparator were eligible. Two investigators independently selected, extracted data from and rated the risk of bias of relevant studies. To compensate for the heterogeneity in outcome measures, simulations were used to summarize the data.
RESULTS: Seven RCTs were included in the review (n = 361), all comparing magnesium to placebo. Three of these trials included only pregnant women. The difference in the median number of leg cramps per week between the placebo and the intervention groups was 0.345 (quantile 2.5%: -0.133, quantile 97.5%: 0.875). This difference was 0.807 (quantile 2.5%: 0.015, quantile 97.5%: 1.207) in the three studies involving only pregnant women and 0.362 (quantile 2.5%: -0.386, quantile 97.5%: 1.148) in the others. Overall gastrointestinal side effects were slightly more common with magnesium therapy than with placebo. The strength of this evidence was weak, mainly due to small study sizes and short follow-up.
CONCLUSIONS: Magnesium therapy does not appear to be effective in the treatment of NLC in the general population, but may have a small effect in pregnant women. Further research using better designed RCTs is necessary.