Meyrick Thomas 1987.

Methods	Double‐blind placebo‐controlled randomized trial Cross‐over design
Participants	10 patients with diagnosis of systemic sclerosis; 1 dropout
Interventions	Participants randomly allocated to group A or B. Following a 4‐week run‐in period during which they received no medication, participants given either oral nifedipine or placebo for 6 weeks. Following a 4‐week drug‐free washout period, participants crossed over to alternative treatment for 6 weeks after completion, with final 4‐week drug‐free washout period Total study duration 20 weeks
Outcomes	Clinical and laboratory assessments performed at regular intervals throughout the trial; in addition, participants completed diary cards recording duration, severity, pain, and date of each attack and any side effects of treatment. Clinical assessment including evaluating compliance, recording lying and standing blood pressures and new digital ulcers, presenting inquiry regarding side effects, and checking completion of diary cards. Venous blood flow taken
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"random order, cross‐over design" Evidence insufficient for judgement of risk
Allocation concealment (selection bias)	Unclear risk	"Patient[s] were randomly allocated to Group A or B." Evidence insufficient for judgement of risk
Blinding of participants and personnel (performance bias) All outcomes	Low risk	"Double‐blind..received either nifedipine or identical placebo capsules 3× daily (Group A or B)"
Blinding of outcome assessment (detection bias) All outcomes	Low risk	"Patient recorded duration, severity, and date of each attack."
Incomplete outcome data (attrition bias) All outcomes	Low risk	1 dropout
Selective reporting (reporting bias)	Unclear risk	None detected
Other bias	Low risk	Cross‐over phases separated by a 4‐week drug‐free washout period