Iran J Pharm Res
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Melatonin has been suggested as a new natural pain killer in inflammatory pain and during surgical procedures. We designed this randomized double-blind controlled study to evaluate the analgesic efficacy and also optimal preemptive dose of melatonin in patients undergoing cesarean section under spinal anesthesia. One hundred twenty patients scheduled for cesarean section under spinal anesthesia were randomly allocated to one of three groups of 40 each to receive melatonin 3 milligram (mg) (group M3), melatonin 6 mg (group M6) or placebo (group P) sublingually 20 min before the spinal anesthesia. ⋯ However, after adjusting headache between groups of the study, we were unable to show the significant difference in the total analgesic request during 24 h after surgery among the three groups (p = 0.058). Although premedication of patients with 3 mg sublingual melatonin prolonged time to first analgesic request after cesarean delivery compared to placebo group, the difference was not statistically significant. Meanwhile increasing dose of melatonin to 6 mg failed to enhance analgesia and also increase the incidence of headache in patients undergoing cesarean section under spinal anesthesia.
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Orexin, mainly produced by orexin-expressing neurons in the lateral hypothalamus (LH), plays an important role in pain modulation. Moreover, it is shown that the nucleus accumbens (NAc) is one of the important areas involved in this modulation. Orexin-1 (OX1) and orexin-2 (OX2) receptors are densely distributed in the NAc. ⋯ Pain scores were calculated at 5-min blocks for a 60-min test period. Results showed that the administration of SB334867 into the NAc decreased LH chemical stimulation-induced antinociception dose-dependently in early and second phase of formalin test. Our findings showed that OX1 receptors in the NAc may be involved in modulation of inflammatory pain.