Diener 2002.

Methods	Double‐blind, parallel group RCT, set in Germany
Participants	94 participants (aged 18 to 70 years) who experienced at least 6 muscle cramps in 2 weeks
Interventions	Quinine sulphate 400 mg daily or placebo for 2 weeks
Outcomes	Cramp number, cramp days, cramp intensity (scale not stated), sleep disturbance (scale not stated), global efficacy rating by participant and doctor (scale not stated), adverse events
Notes	Multicentre trial in Germany; participants taken from 17 general practices
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Randomisation used permuted blocks of four patients stratified by the centre...... when the sealed envelopes were collected and the blind review written, the code was revealed." Comment: probably done
Allocation concealment (selection bias)	Low risk	Quotes: "All investigators enrolled in the study and all participants were unaware of the treatment allocation, because tablets were identical..."; "A sealed envelope assigning either verum or placebo was available in each centre for each patient..." Comment: probably done
Blinding (performance bias and detection bias) All outcomes	Low risk	Quote: "...because the quinine and placebo tablets were identical in appearance."
Incomplete outcome data (attrition bias) All outcomes	High risk	According to the table of results ('Table 2' in the study), there were 6 drop‐outs; none of these are mentioned in the text
Selective reporting (reporting bias)	Low risk	All outcome measures mentioned in the protocol were addressed in the analysis
Other bias	Low risk	Trial completed at designated time period. Well‐matched participant characteristics at baseline