Davis 2000.

Methods	Randomised, placebo‐controlled trial
Participants	28 adult men and women with symptomatic RLS currently on treatment, enrolled from a single neurology clinic (USA)
Interventions	Intervention: ferrous sulfate liquid 325 mg twice a day Placebo: a 50:50 mixture of water and 2% carboxymethlycellulose with a "slightly disagreeable taste, similar to liquid ferrous sulfate". Study drug continued through week 16, then extended an additional 10 weeks if participants preferred study drug to their previous RLS medication
Outcomes	VAS of the extent that RLS interferes with sleep; VAS of how RLS affects life, ferritin, gastrointestinal side effects
Notes	Power for primary outcome was 25%
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Block randomisation, but method not specified
Allocation concealment (selection bias)	Low risk	Randomisation controlled by nurse not involved in the study; randomisation key in locked cabinet
Blinding (performance bias and detection bias) All outcomes	Low risk	Investigators and participants blinded; placebo and iron both liquids with slightly disagreeable taste
Incomplete outcome data (attrition bias) All outcomes	High risk	6 of 14 iron‐treated participants left before primary and secondary outcomes measured at week 14 (versus 1 of 14 placebo‐treated participants). Study data only reported for the people who remained
Selective reporting (reporting bias)	Unclear risk	No study protocol available
Other bias	Low risk	No other risks identified