Summary of findings for the main comparison. Quinine versus placebo for muscle cramps.
| Quinine for muscle cramps | ||||||
| Patient or population: people with muscle cramps Settings: mainly outpatients Intervention: quinine versus 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 | Quinine | |||||
| Number of cramps over 2 weeks | The mean number of cramps over 2 weeks in the control groups was 8.8 cramps | The mean number of cramps over 2 weeks in the intervention groups was 2.45 lower (1.36 to 3.54 lower) | 952 (13 studies) | ⊕⊕⊝⊝ low1 | The difference was statistically significant. | |
| Cramp intensity (on 3‐point scale; 1 = mild; 2 = moderate; 3 = severe) | The mean cramp intensity in the control groups was 1.2 units | The mean cramp intensity in the intervention groups was 0.12 lower (0.2 to 0.05 lower) | 666 (7 studies) | ⊕⊕⊕⊝ moderate1 | The difference was statistically significant. | |
| Participants suffering major adverse events | 14 per 1000 | 15 per 1000 (4 to 35) | See comment | 1103 (18 studies) | ⊕⊕⊕⊝ moderate2 | Risks were calculated from pooled risk differences. The difference was not statistically significant. |
| Participants suffering minor adverse events | 94 per 1000 | 127 per 1000 (94 to 154) | See comment | 969 (16 studies) | ⊕⊕⊕⊝ moderate3 | Risks were calculated from pooled risk differences. The difference was statistically significant. |
| *The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% CI) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). 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. | ||||||
1There were significant shortcomings in study design in some trials, but the majority of those included in this meta‐analysis were of moderate to high quality, warranting a single downgrading for limitations in design and implementation. We further downgraded the evidence for this outcome to low quality because of the heterogeneity of the results.2Major adverse events were defined as those being severe enough to warrant participant withdrawal from the trial. As specific hypersensitivity reactions are so rare, larger studies are needed to clarify the incidence of such adverse events in particular. Some trials did not prespecify adverse events as an outcome but simply reported them retrospectively, thus compromising slightly on the quality of evidence. 3Minor adverse events were defined as being those that did not warrant participant withdrawal from the trial. Some trials did not prespecify adverse events as an outcome but simply reported them retrospectively, thus compromising slightly on the quality of evidence. Otherwise, a well‐reported outcome.