title: Tramadol: pain relief by an opioid without depression of respiration.
abstract: Two independent clinical trials were conducted simultaneously. In one, tramadol and pethidine were compared in 30 patients by patient-controlled analgesia during the first 24 h following abdominal surgery. The mean 24 h consumption of tramadol and pethidine was 642 mg and 606 mg respectively, giving a potency estimate of tramadol relative to pethidine of 0.94 (95% confidence interval 0.72-1.17). In the second trial, the effect on respiration of three doses of tramadol (0.5, 1.0, and 2.0 mg.kg-1) was compared with that of morphine sulphate (0.143 mg.kg-1) by intravenous injection during stable halothane anaesthesia. At approximately 1.5 times the equipotent dose, as estimated from the first trial, tramadol transiently depressed the rate of respiration but had no effect on end-tidal carbon dioxide tension. Morphine caused apnoea or considerable depression of ventilation. The results suggest that mechanisms other than opioid receptor activity play a significant role in the analgesia produced by tramadol.
authors.affiliation: Department of Anaesthetics, University of Wales College of Medicine, Heath Park, Cardiff.
authors.forename: M D
authors.initials: MD
authors.lastname: Vickers
authors.forename: D
authors.initials: D
authors.lastname: O'Flaherty
authors.forename: S M
authors.initials: SM
authors.lastname: Szekely
authors.forename: M
authors.initials: M
authors.lastname: Read
authors.forename: J
authors.initials: J
authors.lastname: Yoshizumi
mesh_terms: D000005:Abdomen / Q000601:surgery; D000328:Adult; D000368:Aged; D016058:Analgesia, Patient-Controlled; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008614:Meperidine / Q000009:adverse effects / Q000627:therapeutic use*; D008875:Middle Aged; D009020:Morphine / Q000627:therapeutic use; D009325:Nausea / Q000139:chemically induced; D010149:Postoperative Pain / Q000188:drug therapy*; D012119:Respiration / Q000187:drug effects*; D014147:Tramadol / Q000009:adverse effects / Q000627:therapeutic use*
chemical_list: D014147:Tramadol; D009020:Morphine; D008614:Meperidine