Comparison 4. Antihistamines vs placebo.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
4.1 Nausea ‐ intraoperative	1	149	Risk Ratio (M‐H, Random, 95% CI)	0.99 [0.47, 2.11]
4.1.1 Dimenhydrinate ‐ 25 mg	1	149	Risk Ratio (M‐H, Random, 95% CI)	0.99 [0.47, 2.11]
4.2 Vomiting ‐ intraoperative	1	149	Risk Ratio (M‐H, Random, 95% CI)	Not estimable
4.2.1 Dimenhydrinate ‐ 25 mg	1	149	Risk Ratio (M‐H, Random, 95% CI)	Not estimable
4.3 Nausea ‐ postoperative	4	514	Risk Ratio (M‐H, Random, 95% CI)	0.44 [0.30, 0.64]
4.3.1 Dimenhydrinate ‐ 25 mg	1	149	Risk Ratio (M‐H, Random, 95% CI)	0.68 [0.31, 1.52]
4.3.2 Dimenhydrate ‐ 50 mg	2	215	Risk Ratio (M‐H, Random, 95% CI)	0.38 [0.21, 0.69]
4.3.3 Dimenhydrate ‐ 100 mg	1	90	Risk Ratio (M‐H, Random, 95% CI)	0.17 [0.05, 0.57]
4.3.4 Cyclizine ‐ 50 mg	1	60	Risk Ratio (M‐H, Random, 95% CI)	0.50 [0.28, 0.88]
4.4 Vomiting ‐ postoperative	3	333	Risk Ratio (M‐H, Random, 95% CI)	0.48 [0.29, 0.81]
4.4.1 Dimenhydrinate ‐ 25 mg	1	149	Risk Ratio (M‐H, Random, 95% CI)	0.13 [0.01, 2.48]
4.4.2 Dimenhydrate ‐ 50 mg	1	124	Risk Ratio (M‐H, Random, 95% CI)	0.52 [0.19, 1.42]
4.4.3 Cyclizine ‐ 50 mg	1	60	Risk Ratio (M‐H, Random, 95% CI)	0.50 [0.27, 0.93]
4.5 Hypotension	1	149	Risk Ratio (M‐H, Random, 95% CI)	1.47 [0.90, 2.40]
4.5.1 Dimenhydrinate ‐ 25 mg	1	149	Risk Ratio (M‐H, Random, 95% CI)	1.47 [0.90, 2.40]