A Cochrane review included 7 studies with a total of 406 subjects. Five trials were parallel and 2 cross-over design. Four trials enrolled idiopathic cramp sufferers (n=322 including cross-over controls) and 3 trials enrolled women with pregnancy-associated leg cramps (n=202). Magnesium (Mg) was compared to placebo in 6 trials and to no treatment in one trial. No RCTs evaluating Mg for exercise-associated or disease-associated muscle cramps have been conducted. For idiopathic cramps (largely older adults presumed to have nocturnal leg cramps), differences between Mg vs. placebo in measures of cramp frequency were not statistically significant. This includes the primary endpoint, percentage change from baseline in the number of cramps per week at 4 weeks (-3.93%, 95% CI -21.12% to 13.26%; 2 trials, n=83) and the difference in the number of cramps per week at 4 weeks (0.01 cramps/week, 95% CI -0.52 to 0.55; 4 trials, n=101). The percentage of individuals experiencing a 25% or better reduction in cramp rate from baseline was also not different, being 8% lower in the Mg group (95% CI -28% to 12%; 2 trials, n=83). Similarly, no statistically significant difference was found at 4 weeks in measures of cramp intensity or duration. Meta-analysis was not possible for trials of pregnancy-associated leg cramps. The single study comparing Mg to no treatment did not find statistically significant benefit on a 3-point ordinal scale of overall treatment efficacy. Two trials comparing Mg to placebo differed in that one trial found no benefit on frequency or intensity measures while the other found benefit for both. Withdrawals due to adverse events were not significantly different than placebo.
Comment: The quality of the evidence is downgraded by study quality (unclear allocation concealment) and imprecise results (few patients with wide confidence intervals).
Date of latest search: