Sidorov 1993.

Methods	Double‐blind RCT of cross‐over design, set in USA
Participants	19 adult participants from general medicine clinic who experienced at least 2 leg cramps per week
Interventions	2‐week run‐in period, followed by either quinine bisulphate 200 mg at night or placebo daily for 3 weeks before cross‐over to a second 3‐week treatment period
Outcomes	Cramp number, cramp intensity (graded 1 = mild to 10 = severe), cramp duration (seconds), adverse events
Notes	Single centre. Conducted in USA
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Randomisation was accomplished using a simple random numbers table..." Comment: probably adequate
Allocation concealment (selection bias)	High risk	No evidence that allocations were concealed
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Quote: "Patients were blinded to all study periods. However, study personnel were aware that periods one and three used placebo." Comment: details of how investigators and participants were blinded not provided
Incomplete outcome data (attrition bias) All outcomes	Low risk	All 6 participants who left the study were accounted for
Selective reporting (reporting bias)	Low risk	All outcome measures mentioned in the methods were addressed in the analysis
Other bias	Unclear risk	The study group who successfully completed the study consisted of 14 women and only 2 men