title: Interaction between tramadol and two anti-emetics on nociception and gastrointestinal transit in mice.
abstract: BACKGROUND
  Clinical studies suggest that tramadol-induced analgesia is partially antagonized by ondansetron.
  
  
  OBJECTIVE
  To investigate the type of interaction between tramadol and two anti-emetics on antinociception and gastrointestinal transit in mice.
  
  
  METHODS
  We assessed the antinociceptive (acetic acid writhing test, plantar test) and antitransit (charcoal meal) effects of tramadol individually, and combined with ondansetron or droperidol in female Swiss CD-1 mice. Isobolograms and analysis of variance were used to determine the type of interaction.
  
  
  RESULTS
  In the writhing test, tramadol, ondansetron and droperidol, each induced dose-related inhibition of nociception. The ED(50)'s were: tramadol 4.2+/-0.33 mg kg(-1); ondansetron 1.03+/-0.05 mg kg(-1), and droperidol 1.00+/-0.14 mg kg(-1). Dose-response curves were also obtained with tramadol combined with ondansetron or droperidol at 1:1 fixed ratios. The isobolographic analysis demonstrated antagonism for both combinations. In the plantar test, the ED(50) for tramadol was 51.4+/-2.3 mg kg(-1), but no dose-response curves could be obtained with ondansetron or droperidol individually. The interaction was assessed from dose-response curves to tramadol in the presence of a fixed dose of ondansetron (0.1 mg kg(-1)) or droperidol (0.05 mg kg(-1)). The results show antagonism between tramadol-ondansetron (p<0.05) and no interaction for the tramadol-droperidol combination. Both anti-emetics antagonized the antitransit effects of tramadol.
  
  
  CONCLUSIONS
  The interaction of tramadol with ondansetron or droperidol on antinociception can be antagonistic or additive, depending on the type of stimuli. Both anti-emetics antagonize the anti-transit effects of tramadol. The results demonstrate antagonism between tramadol and the two anti-emetics for analgesia and inhibition of gastrointestinal transit, supporting previous clinical studies.
authors.affiliation: Department of Anaesthesiology, Hospital Universitario del Mar, Universidad Autónoma de Barcelona, Paseo Marítimo 25, 08003 Barcelona, Spain.
authors.forename: Christian
authors.initials: C
authors.lastname: Dürsteler
authors.forename: Anna
authors.initials: A
authors.lastname: Mases
authors.forename: Victor
authors.initials: V
authors.lastname: Fernandez
authors.forename: Olga
authors.initials: O
authors.lastname: Pol
authors.forename: Margarita M
authors.initials: MM
authors.lastname: Puig
mesh_terms: D000701:Analgesics, Opioid / Q000009:adverse effects / Q000037:antagonists & inhibitors; D000818:Animals; D000932:Antiemetics / Q000009:adverse effects / Q000494:pharmacology; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004329:Droperidol / Q000009:adverse effects / Q000494:pharmacology*; D004347:Drug Interactions; D005260:Female; D005772:Gastrointestinal Transit / Q000187:drug effects* / Q000502:physiology; D051379:Mice; D017294:Ondansetron / Q000009:adverse effects / Q000494:pharmacology*; D010146:Pain / Q000188:drug therapy* / Q000503:physiopathology; D010147:Pain Measurement / Q000187:drug effects; D020250:Postoperative Nausea and Vomiting / Q000139:chemically induced* / Q000188:drug therapy / Q000503:physiopathology; D044406:Receptors, Serotonin, 5-HT3 / Q000378:metabolism; D058831:Serotonin 5-HT3 Receptor Antagonists; D012702:Serotonin Antagonists / Q000009:adverse effects / Q000494:pharmacology; D014147:Tramadol / Q000009:adverse effects / Q000037:antagonists & inhibitors*
chemical_list: D000701:Analgesics, Opioid; D000932:Antiemetics; D044406:Receptors, Serotonin, 5-HT3; D058831:Serotonin 5-HT3 Receptor Antagonists; D012702:Serotonin Antagonists; D014147:Tramadol; D017294:Ondansetron; D004329:Droperidol