Roffe 2002.

Methods	Double blind RCT of cross‐over design
Participants	73 non‐pregnant rest cramp sufferers (mean age 63 yrs), having at least 2 cramps per week. Recruitment by community advertizement in a UK population
Interventions	Either 1830 mg of tri‐magnesium dicitrate powder (300 mg elemental magnesium) poured from a sachet into a glass of water, or matched placebo powder, taken orally each night for 6 weeks before switching to the alternate therapy. 2 week magnesium free run‐in and effectively a 2 week washout between treatments since only the last 4 weeks of each 6 weeks on treatment was used for outcome assessment
Outcomes	Number of cramps during the last 4 weeks of each treatment period. Severity of cramps (mild, moderate, severe). Duration of cramps (short, medium, long). Self reported assessment of treatment effectiveness (yes, no)
Notes	Published. Manufacturer sponsored. Only data from the first period have been used in this review because large differences in treatment effect are seen depending on the sequence in which treatment is given. Patient level data provided by the principle investigator.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The manufacturer provided centralized randomization for the trial in large blocks of 10. Specifics regarding the sequence generation were not given. The resulting allocation was unequal with more subjects included in the analysis receiving magnesium second (29 vs 17).
Allocation concealment (selection bias)	Low risk	Quote: "The randomisation code was not known to the investigators who gave out the sachets. The code remained concealed from everyone except the pharmacist who prepared the sachets..." Comment: Satisfactory concealment
Blinding (performance bias and detection bias) All outcomes	Unclear risk	No description of whether the magnesium and placebo suspensions tasted different
Incomplete outcome data (attrition bias) All outcomes	High risk	Reasons for dropout documented, but 27 of 73 subjects (37%) did not complete the study
Selective reporting (reporting bias)	Low risk	Severity and duration of cramps were described only as not being different (i.e. no numbers given), however, these data were provided to us by the authors.
Cramp diary (recall bias)	Low risk	Diary used
Other bias	Unclear risk	Manufacturer played an active role in the trial. There was a large difference in treatment effect depending on the sequence of treatments (much greater benefit if treatment was received in the order placebo→magnesium). Unclear if this difference was due entirely to period effect or if noncompleters, the potential for carry‐over or unblinding contributed. This difference in benefit resulting from treatment order was important since the randomization was unbalanced (many more subjects receiving the placebo→magnesium sequence).