title: Effect of intravenous administration of tramadol hydrochloride on the minimum alveolar concentration of isoflurane in rabbits.
abstract: OBJECTIVE
  To evaluate the effect of IV administration of tramadol hydrochloride on the minimum alveolar concentration of isoflurane (ISOMAC) that prevented purposeful movement of rabbits in response to a noxious stimulus.
  
  
  METHODS
  Six 6- to 12-month-old female New Zealand White rabbits.
  
  
  METHODS
  Anesthesia was induced and maintained with isoflurane in oxygen. A baseline ISOMAC was determined by clamping a pedal digit with sponge forceps until gross purposeful movement was detected or a period of 60 seconds elapsed. Subsequently, tramadol (4.4 mg/kg) was administered IV and the posttreatment ISOMAC (ISOMAC(T)) was measured.
  
  
  RESULTS
  Mean +/- SD ISOMAC and ISOMAC(T) values were 2.33 +/- 0.13% and 2.12 +/- 0.17%, respectively. The ISOMAC value decreased by 9 +/- 4% after tramadol was administered. Plasma tramadol and its major metabolite (M1) concentrations at the time of ISOMAC(T) determination varied widely (ranges, 181 to 636 ng/mL and 32 to 61 ng/mL, respectively). Intervals to determination of ISOMAC(T) and plasma tramadol and M1 concentrations were not correlated with percentage change in the ISOMAC. Heart rate decreased significantly immediately after tramadol administration but by 10 minutes afterward was not different from the pretreatment value. Systolic arterial blood pressure decreased to approximately 60 mm Hg for approximately 5 minutes in 3 rabbits after tramadol administration. No adverse effects were detected.
  
  
  CONCLUSIONS
  As administered, tramadol had a significant but clinically unimportant effect on the ISOMAC in rabbits. Higher doses of tramadol may provide clinically important reductions but may result in a greater degree of cardiovascular depression.
authors: Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996, USA.
authors: Christine M
authors: CM
authors: Egger
authors: Marcy J
authors: MJ
authors: Souza
authors: Cheryl B
authors: CB
authors: Greenacre
authors: Sherry K
authors: SK
authors: Cox
authors: Barton W
authors: BW
authors: Rohrbach
mesh_terms: D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000494:pharmacology*; D018685:Anesthetics, Inhalation / Q000378:metabolism*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D007530:Isoflurane / Q000097:blood*; D010812:Physical Stimulation; D011817:Rabbits; D013997:Time Factors; D014147:Tramadol / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*
chemical_list: D000701:Analgesics, Opioid; D018685:Anesthetics, Inhalation; D014147:Tramadol; D007530:Isoflurane