Jones 1983.

Methods	Double‐blind RCT of cross‐over design, UK
Participants	9 elderly participants seeking treatment from GP for at least 2 cramp nights per week
Interventions	Quinine sulphate 300 mg or placebo daily for a 2‐week treatment period, followed by a 2‐week washout period before cross‐over to a second 2‐week treatment period. A 2‐week run‐in period (of placebo) preceded the first phase of treatment
Outcomes	Improvement in sleep induction (graded 1 = difficult to 10 = easy), sleep quality (graded 1 = poor to 10 = good), cramp severity (graded 1 = mild to 10 =severe), cramp timing (before or after 2 am), cramp duration and adverse events
Notes	Table of results for cramp duration contradicts commentary in Results section
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "The study was double‐blind and crossed over within patients, and randomised..." Comment: details of randomisation not provided
Allocation concealment (selection bias)	Low risk	Quote: "...the study was... randomised and balanced by an independent observer." Comment: probably adequate concealment
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Quote: "The study was double‐blind.... the two weeks between treatments were single‐blind with patients taking placebo." Comment: no explicit mention of how blinding was achieved
Incomplete outcome data (attrition bias) All outcomes	Low risk	All 9 participants completed the trial
Selective reporting (reporting bias)	Low risk	All outcome measures commented upon in analysis, including adverse events
Other bias	Low risk	Adequate washout periods. Trial ended at designated time period