There were 55 placebo and verum (positive control) controlled studies, using a randomised, double-blind cross-over design (number of participants not stated).
Results were only provided for selected antihistamines (authors do not state what criteria were used in the selection process):
Risk benefit ratio for all tests combined (number of tests showing no impairment, no of tests showing impairment):
Fexofenadine: 0.00 (31, 0).
Ebastine: 0.00 (14, 0).
Cetirizine: 0.21 (70, 15).
Loratadine: 0.29 (38, 11).
Mizolastine: 0.50 (34, 25).
Chlorpheniramine: 7.67 (3, 23).
Diphenhydramine: 27.50 (2, 55).
Triprolidine: 60.00 (1, 60).
Risk benefit ratio for subjective tests:
Fexofenadine: 0.00 (6, 0).
Ebastine: 0.00 (5, 0).
Cetirizine: 0.32 (22, 7).
Loratadine: 0.07 (12, 1).
Mizolastine: 0.40 (5, 2).
Chlorpheniramine: Not done (0, 9).
Diphenhydramine: Not done (2, 19).
Triprolidine: 14.0 (1, 14).
Risk benefit ratio objective tests:
Fexofenadine: 0.00 (25, 0).
Ebastine: 0.00 (9, 0).
Cetrizine: 0.17 (48, 8).
Loratadine: 0.38 (26, 10).
Mizolastine: 0.52 (29, 15).
Chlorpheniramine: 4.67 (3, 14).
Diphenhydramine: 18.0 (0, 36).
Triprolidine: Not done (0, 46).