Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
Headache
RCT Crossover design	42 people with primary (17 people) and secondary (15 people) Raynaud's phenomenon	Headache 26/32 (81%) with glyceryl trinitrate 10/32 (31%) with placebo	P <0.001 Result should be interpreted with caution; see further information on studies for full details	Effect size not calculated	placebo
Withdrawals
RCT Crossover design	42 people with primary (17 people) and secondary (15 people) Raynaud's phenomenon	Withdrawals with glyceryl trinitrate with placebo	Significance not assessed