Roca 1992.

Methods	Double‐blind, parallel group RCT, set in Ohio, USA
Participants	30 participants on dialysis, with a history of leg cramps
Interventions	2‐month placebo run‐in period, then active phase of either daily quinine 325 mg at bedtime with a vitamin E placebo, or vitamin E 400 IU at bedtime with a quinine placebo, for 2 months
Outcomes	Cramp number, cramp intensity (graded 1 = no pain to 6 = excruciating), adverse events
Notes	29 participants (aged 21 to 73 years) from a community‐based academic hospital in Ohio, USA, completed the study. Study compares quinine to vitamin E as well as vitamin E and quinine to placebo. Although researchers state adverse effects of interventions will be investigated, no mention is made of these in the Results or Discussion
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "Patients were then randomized into two groups..." Comments: no description of randomisation protocol
Allocation concealment (selection bias)	Unclear risk	No details regarding how allocation may have been concealed is given
Blinding (performance bias and detection bias) All outcomes	Low risk	Quote: "quinine 325 mg at bedtime with a vitamin E placebo or 2) vitamin E 400 IU at bedtime with a quinine placebo." Comment: probably done
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	11 of 40 participants did not complete the trial, all of whom were accounted for. However, 1 participant died after randomisation but no details were given about which treatment was received or whether the death was related to the medication given
Selective reporting (reporting bias)	High risk	Adverse events were an outcome but no results given. Also results are given only for first month of treatment, despite treatment duration being 60 days
Other bias	Low risk