Hays 1986.

Methods	Double‐blind RCT of cross‐over design, set in Florida USA
Participants	62 participants (mean age 47 years) who experienced at least 2 leg cramps per week
Interventions	2‐week baseline then 2 weeks of quinine sulphate (325 mg) or placebo, then 2‐week washout, then 2 weeks of cross‐over treatment, then 2‐week washout
Outcomes	Cramp number, cramp intensity, cramp days, adverse events
Notes	Second trial by Scholl pharmaceuticals submitted to FDA, but with higher quinine dose of 325 mg. Unpublished.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "...medications will be assigned according to a predetermined randomization schedule" Comment: no details of the "randomization schedule" are provided
Allocation concealment (selection bias)	Low risk	Quote: "Each subject's medications will be provided by the Sponsor and distributed by the Invesitgator" Comment: appears that allocation was concealed
Blinding (performance bias and detection bias) All outcomes	Low risk	Quote: "Placebo capsules...will be identical in appearance"
Incomplete outcome data (attrition bias) All outcomes	Low risk	All withdrawals were accounted for
Selective reporting (reporting bias)	Low risk	All outcomes reported on
Other bias	Unclear risk	Conducted by manufacturer of quinine tablets