Garrison 2011.

Methods	Double‐blind, parallel group RCT
Participants	46 non‐pregnant rest cramp sufferers (mean age 69.3 yrs) with at least 8 cramps in a 30 day baseline diary. Recruitment from posters and pamphlets in 21 Canadian (Richmond BC) family practitioner offices and also by newspaper advertizement
Interventions	5 days consecutive 4 hour intravenous infusions of 250 ml D5W (5% dextrose in water) either with (treatment group) or without (control group) 20 mmol of magnesium sulfate added (20 mmol = 486 mg elemental magnesium). Indistinguishable.
Outcomes	Primary: Change in the number of cramps per week from baseline at 30 days. Secondary: Change in the number of cramps per week from baseline at 90 days. Percentage change in cramps / wk. Cramp pain (1 to 10 interval scale). Cramp duration on a 3‐point ordinal scale (1 = < 1 minute, 2 = 1‐5 minutes, 3 = > 5 minutes).  24‐h urinary magnesium on days 1 and 5 to determine % retention of infused magnesium.
Notes	Published. Independent funding.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Randomization, using a computer generated random allocation sequence without any blocking or stratification was carried out by the hospital pharmacist dispensing the study drugs according to a series of opaque allocation envelopes kept in the pharmacy." Comment: Satisfactory randomization
Allocation concealment (selection bias)	Low risk	Quote: "All investigators, study nurses and subjects were blinded as to treatment allocation." Comment: Satisfactory allocation concealment
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Quote: 1) "Active and Placebo solutions were indistinguishably clear and colorless." 2) "Subjects had been told that IV site discomfort was possible with both placebo and Mg infusions. While generally it was considered that blinding was reasonable, the sensation of burning at the IV site, coupled with the additional saline dilution in some Mg subjects, could have compromised the blind to some extent (presumably favouring the intervention)."
Incomplete outcome data (attrition bias) All outcomes	Low risk	No drop‐outs or losses to follow‐up. Analysis was intention‐to‐treat.
Selective reporting (reporting bias)	Low risk	Did not process urine samples for magnesium on those getting placebo (although did a reasonable job collecting urine samples from all patients to make sure the blinding was not broken). Severity and duration of cramps were described only as not being different (i.e. no numbers given), however, these data were made available by the authors.
Cramp diary (recall bias)	Low risk	Diary used
Other bias	Low risk	No obvious other bias