Fung 1989.

Methods	Double‐blind RCT of cross‐over design, set in Utah, USA
Participants	9 elderly outpatients with a history of night cramps of at least 1 year, with at least 2 cramps per week
Interventions	Quinine sulphate 200 mg or placebo at bedtime for a 4‐week treatment period, followed by a 1‐week washout period before cross‐over to a second 4‐week treatment period
Outcomes	Cramp number, cumulative duration of attacks (in minutes), cumulative score of cramp severity (graded 1 = mild to 3 = severe), adverse events
Notes	The cumulative duration of cramps was calculated as was the score for intensity. Duration or intensity per cramp was not calculated. However, these were calculated from individual patient data. Recruitment in June to December 1987
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "...and patients were randomly assigned.." Comment: no details of the randomisation process are provided
Allocation concealment (selection bias)	Unclear risk	No details provided on how allocation was concealed
Blinding (performance bias and detection bias) All outcomes	Low risk	Quote: "in a double‐blind manner to begin receiving either quinine or a placebo." Comment: probably done
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Explanation given for the one drop‐out, but was not included in analysis on an intention‐to‐treat basis
Selective reporting (reporting bias)	Low risk	All intended outcome measures are addressed in the results
Other bias	Unclear risk	7 of the 8 volunteers who completed the trial were women