Study	Reason for exclusion
Achkar 1995	Review
Allescher 1993	Review
Bassotti 1988	No control
Bassotti 1999	Review
Bortolotti 1994	Non‐randomized controlled trial
Bourgeois 1992	No intervention with nitrates
Douthwaite 1943	Non‐randomised controlled trial
Efrati 1996	Case‐report
Ferguson 1981	Performed on participants with chest pain
Furuya 1995	Case‐report
Gelfond 1981	No control
Ghosh 1994	No control
Hildebrand 1993	Review
Kikendall 1980	Study performed on healthy volunteers
Krivchenya 1990	No control medication
Ona 1980	Case report
Reynolds 1989	Review
Rozen 1982a	No control
Rozen 1982b	No control
Schroeder 1985	Review
Stanley 1955	A group of participants with cardiospasm were given urecholine, dibuline, and finally nitroglycerin. The author did not provide the exact time interval between each medicine and did not provide exactly how long after nitroglycerin intake participants were measured for oesophageal emptying.
Storr 1999	Review
Swamy 1977	Performed on participants with esophageal spasm, no control medication.
Tack 1991	Review
Traube 1985	Review
Vaezi 1998	Review
Wang 1988	No control medication