title: Preoperative anxiolytic effect of melatonin and clonidine on postoperative pain and morphine consumption in patients undergoing abdominal hysterectomy: a double-blind, randomized, placebo-controlled study.
abstract: Recent evidence has demonstrated analgesic, anti-inflammatory, and anxiolytic properties of melatonin. Taking into account that higher anxiety makes the control of postoperative pain more difficult, one can hypothesize that melatonin anxiolytic and analgesic effects improve the control of postoperative pain. Thus, we conducted a randomized, double-blind, placebo-controlled study with 59 patients undergoing abdominal hysterectomy to test the hypothesis that melatonin is as effective as clonidine and that both are more effective than placebo in reducing postoperative pain. Additionally, we compared their anxiolytic effects on postoperative pain. Patients were randomly assigned to receive oral melatonin (5 mg) (n = 20), clonidine (100 microg) (n = 19), or placebo (n = 20) orally. In addition to primary outcomes of pain intensity and analgesic consumption, secondary outcome measures included postoperative state anxiety. In anxious patients 6 hours after surgery, the number of patients needed to be to prevent moderate to intense pain during the first 24 hours after surgery was 1.52 (95% CI, 1.14 to 6.02) and 1.64 (95% CI, 1.29 to 5.93), respectively, in the melatonin and clonidine groups compared with placebo. Also, the anxiolytic effect of melatonin and clonidine resulted in reduced postoperative morphine consumption by more than 30%. However, in the mildly anxious, it was not observed the treatment effect on pain.
  
  
  CONCLUSIONS
  The preoperative anxiolysis with melatonin or clonidine reduced postoperative pain and morphine consumption in patients undergoing abdominal hysterectomy. The effects these 2 drugs were equivalent and greater than with placebo.
authors.affiliation: Anesthesia Service and Perioperative Medicine, Hospital de CLíNICAS DE Porto Alegre/Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil. caumo@cpovo.net
authors.forename: Wolnei
authors.initials: W
authors.lastname: Caumo
authors.forename: Rosa
authors.initials: R
authors.lastname: Levandovski
authors.forename: Maria Paz L
authors.initials: MP
authors.lastname: Hidalgo
mesh_terms: D000284:Administration, Oral; D000328:Adult; D000700:Analgesics / Q000008:administration & dosage / Q000627:therapeutic use; D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000627:therapeutic use; D000704:Analysis of Variance; D001007:Anxiety / Q000517:prevention & control / Q000523:psychology; D002492:Central Nervous System Depressants / Q000008:administration & dosage / Q000627:therapeutic use; D003000:Clonidine / Q000008:administration & dosage / Q000627:therapeutic use*; D004311:Double-Blind Method; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D007044:Hysterectomy / Q000379:methods*; D008550:Melatonin / Q000008:administration & dosage / Q000627:therapeutic use*; D008875:Middle Aged; D009020:Morphine / Q000008:administration & dosage / Q000627:therapeutic use*; D010147:Pain Measurement / Q000379:methods; D017288:Pain Threshold / Q000187:drug effects; D010149:Postoperative Pain / Q000517:prevention & control* / Q000523:psychology; D010919:Placebos; D011300:Preoperative Care / Q000379:methods; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D000700:Analgesics; D000701:Analgesics, Opioid; D002492:Central Nervous System Depressants; D010919:Placebos; D009020:Morphine; D008550:Melatonin; D003000:Clonidine