Warburton 1987.

Methods	Double‐blind RCT of cross‐over design
Participants	22 elderly outpatients (mean age 74 years), seeking treatment for leg cramps
Interventions	Quinine bisulphate 300 mg or placebo daily for a 3‐week treatment period, followed by immediate cross‐over onto another 3‐week treatment period (i.e. no washout period inbetween). A 2‐week run‐in period before the trial involved quinine abstention
Outcomes	Cramp number, "cramp index" (the product of intensity score 1 = mild to 3 = severe and duration < 1 min = 1, 1 to 10 min = 2, 11 to 20 min = 3, 21 to 60 min = 4, or > 60 min = 5), adverse events
Notes	Cramp duration and intensity could not be separated from the "cramp index". Individual patient data were available
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "the remainder were allocated, using a table of random numbers..." Comment: probably adequate
Allocation concealment (selection bias)	Unclear risk	No details given regarding allocation concealment
Blinding (performance bias and detection bias) All outcomes	Low risk	Quote: "Treatments were quinine, 300 mg, at night, or an identical, sugar coated placebo tablet..." Comment: satisfactory blinding
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	1 participant dropped out during the placebo stage for an unspecified reason and was not included in the final analysis
Selective reporting (reporting bias)	Low risk	All outcome measures mentioned in the protocol were addressed in the analysis
Other bias	High risk	Quote: "followed by two, sequential, 3‐week treatment periods." Comment: no washout period between each treatment phase raises the possibility of significant carry‐over effect