for the main comparison.
| Magnesium for skeletal muscle cramps | ||||||
|
Patient or population: Nonpregnant patients with muscle cramps (largely older adults) Settings: Outpatients recruited through primary care clinics or community advertising Intervention: Magnesium supplements (oral or intravenous) Comparison: Placebo | ||||||
| Outcomes | Illustrative comparative risks* (95% CI) | Relative effect (95% CI) | No of Participants (studies) | Quality of the evidence (GRADE) | Comments | |
| Assumed risk | Corresponding risk | |||||
| Placebo | Magnesium | |||||
| Percentage change in cramp frequency from baseline at 4 weeks | The mean percentage change in cramp frequency in the control groups was ‐27.8% (i.e. a 27.8% reduction) | The mean percentage change in cramp frequency in the magnesium groups was 3.9% lower | ‐3.9% (‐21.1 to 13.3) |
83 (2 studies) | ⊕⊕⊕⊝ moderate | This difference was neither clinically nor statistically significant. The 95% confidence interval excludes a 25% reduction beyond placebo |
| Percentage of participants with a ≥ 25% reduction in their cramp frequency at 4 weeks | The mean percentage of placebo recipients achieving a 25% or better reduction in the frequency of their cramps was 65.9% | The mean percentage of magnesium recipients achieving a 25% or better reduction in the frequency of their cramps was 8% lower | ‐8% (‐28% to 12%) |
83 (2 studies) | ⊕⊕⊕⊝ moderate | This difference was neither clinically nor statistically significant |
| Number of cramps per week at 4 weeks | The mean number of cramps per week in the placebo groups while on treatment was 4.35 | The mean number of cramps per week in the magnesium groups was 0.01 cramps per week higher | 0.01 cramps per week (‐0.52 to 0.55) |
213 (4 studies) | ⊕⊕⊕⊝ moderate | This difference was neither clinically nor statistically significant. The 95% confidence interval excludes a 1 cramp per week reduction |
| Percentage of participants rating their cramps as moderate or severe (i.e. mean cramp intensity ≥ 2 on the 3 point intensity scale) at 4 weeks | The mean percentage of placebo recipients rating their cramps as moderate or severe was 30% | The mean percentage of magnesium recipients rating their cramps as moderate or severe was 9% greater | 9% (‐7% to 25%) |
91 (2 studies) |
⊕⊕⊕⊝ moderate | This difference was neither clinically nor statistically significant |
| Percentage of participants with the majority of cramp durations ≥ 1 minute at 4 weeks | The mean percentage of placebo recipients with the majority of cramp durations ≥ 1 minute was 22.7% | The mean percentage of magnesium recipients with the majority of cramp durations ≥ 1 minute was 19% greater | 19% (‐7% to 45%) |
46 (1 study) | ⊕⊕⊝⊝ low | This difference was neither clinically nor statistically significant |
| Number of participants with major adverse events | 1 out of 22 | 0 out of 24 | ‐50 per 1000 (‐160 to 70) | 46 (1 study) |
⊕⊝⊝⊝ very low | This difference was neither clinically nor statistically significant |
| Number of participants with minor adverse events | Adverse events were not reported in a way that permitted the number of participants with minor adverse events to be determined. Each study of oral magnesium inferred that side effects were similar in frequency to placebo. Intravenous magnesium was associated with asymptomatic hypotension (3/24 magnesium versus 0/22 placebo recipients), transient light‐headedness (2/24 magnesium versus 0/22 placebo) and burning of the IV site (12/24 magnesium versus 0/22 placebo). | |||||
| CI: Confidence interval; | ||||||
| GRADE Working Group grades of evidence High quality: Further research is very unlikely to change our confidence in the estimate of effect. Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. Very low quality: We are very uncertain about the estimate. | ||||||
Downgrading of the quality of evidence is based largely on the number of studies and participants contributing to each estimate. The quality of evidence for the number of participants with major adverse events is considered very low because such events are rare.