Table 1.

Summary of the included trials.

Study ID	Design	Country	Interventions	Time	Dose	Type of Anesthesia	Administration Route	Sample Size	Follow-Up
Kiabi 2021 [30]	RCT	Iran	Melatonin	1 h before surgery	5 mg	Spinal anesthesia	Oral	68	24 h after surgery
					10 mg		Oral	68
			Placebo		NA		Oral	68
Khezri 2019 [29]	RCT	Iran	Melatonin	20 min before the spinal anesthesia	3 mg	Spinal anesthesia	Sublingual	40	12 h after surgery
					6 mg		Sublingual	40
			Placebo		NA		Sublingual	40
Khezri 2016 [16]	RCT	Iran	Melatonin	20 min before the spinal anesthesia	3 mg	Spinal anesthesia	Sublingual	40	12 h after surgery
					6 mg		Sublingual	40
			Placebo		NA		Sublingual	40
Jayashree 2021 [36]	RCT	India	Melatonin	20 min before the skin incision	6 mg	NR	Sublingual	30	NR
			Placebo		NA		Sublingual	30
Jahromi 2016 [37]	RCT	Iran	Melatonin	1 h before spinal anesthesia	3 mg	Spinal anesthesia	Oral	20	NR
			Placebo		NA		Oral	20
Gowda 2022 [38]	RCT	India	Melatonin	1 h before spinal anesthesia	3 mg	Spinal anesthesia	Oral	30	12 h after surgery
			Placebo		NA		Oral	30
Boroojeny 2020 [39]	RCT	Iran	Melatonin	2 h before spinal anesthesia	1.5 mg	Spinal anesthesia	Oral	50	24 h after surgery
					3 mg		Oral	50
			Placebo		NA		Oral	50

RCT: randomized controlled trial; NA: not applicable; NR: not reported.