Leo Winter 1986.

Methods	Double‐blind RCT of cross‐over design, set in New York and California, USA
Participants	205 participants (mean age 44 years) who experienced at least 2 leg cramps per week
Interventions	1‐week washout then 4 blocks of 5‐day treatment periods separated by 2‐day washouts. Treatments consisted of 129.6 mg quinine sulphate twice daily, or a quinine‐vitamin E combination (129.6 mg quinine sulphate plus 800 Units vitamin E) twice daily, or 800 units vitamin E twice daily
Outcomes	Cramp number, cramp intensity, cramp days, sleep disturbance, adverse events.
Notes	The second largest trial. 2‐centre trial (New York & California). NB short treatment periods. Unpublished
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "...patients were assigned at random to 24 treatment sequences according to a randomisation schedule" Comment: no details of how the "randomisation schedule" was generated
Allocation concealment (selection bias)	Low risk	Quote: "...according to a randomisation schedule prepared by an independent person who did not participate in the study" Comment: appears adequate
Blinding (performance bias and detection bias) All outcomes	Low risk	Quote: "...under the double‐blind condition for identically appearing study medications"
Incomplete outcome data (attrition bias) All outcomes	Low risk	All withdrawals and those lost to follow‐up were fully accounted for
Selective reporting (reporting bias)	Low risk	All outcomes are reported in the results
Other bias	High risk	High risk of bias caused by very short washout periods between treatments. Also, trial conducted by manufacturer of quinine tablets