Table 4.

Use of melatonin and analgesic consumption change in the subgroup meta-analysis of randomized, double-blind, placebo-controlled trials.

Type of Pain	No. of Low Risk of Bias	No. of Trials	Summary SMD (95% CI)	Heterogeneity, I2 (%)
Acute pain—procedural	≥ 6	2 [32,33]	−0.527 (−1.517, 0.464)	84.0
	< 6	1 [23]	−3.262 (−3.818, −2.706)	NA
Acute pain—postoperative, general anesthesia	≥ 6	4 [12,18,19,20]	−4.676 (−7.546, −1.806)	97.9
	< 6	3 [13,25,30]	−1.271 (−2.087, −0.455)	83.6

Abbreviation: NA, not applicable; SMD, standardized mean difference; CI, confidence interval.