title: Percutaneous sciatic nerve block with tramadol induces analgesia and motor blockade in two animal pain models.
abstract: Local anesthetic efficacy of tramadol has been reported following intradermal application. Our aim was to investigate the effect of perineural tramadol as the sole analgesic in two pain models. Male Wistar rats (280-380 g; N = 5/group) were used in these experiments. A neurostimulation-guided sciatic nerve block was performed and 2% lidocaine or tramadol (1.25 and 5 mg) was perineurally injected in two different animal pain models. In the flinching behavior test, the number of flinches was evaluated and in the plantar incision model, mechanical and heat thresholds were measured. Motor effects of lidocaine and tramadol were quantified and a motor block score elaborated. Tramadol, 1.25 mg, completely blocked the first and reduced the second phase of the flinching behavior test. In the plantar incision model, tramadol (1.25 mg) increased both paw withdrawal latency in response to radiant heat (8.3 ± 1.1, 12.7 ± 1.8, 8.4 ± 0.8, and 11.1 ± 3.3 s) and mechanical threshold in response to von Frey filaments (459 ± 82.8, 447.5 ± 91.7, 320.1 ± 120, 126.43 ± 92.8 mN) at 5, 15, 30, and 60 min, respectively. Sham block or contralateral sciatic nerve block did not differ from perineural saline injection throughout the study in either model. The effect of tramadol was not antagonized by intraperitoneal naloxone. High dose tramadol (5 mg) blocked motor function as well as 2% lidocaine. In conclusion, tramadol blocks nociception and motor function in vivo similar to local anesthetics.
authors.affiliation: LIM-Anestesiologia Experimental, Faculdade de Medicina, Universidade de São Paulo, Brasil. angela.sousa@icesp.org.br
authors.forename: A M
authors.initials: AM
authors.lastname: Sousa
authors.forename: H A
authors.initials: HA
authors.lastname: Ashmawi
authors.forename: L S
authors.initials: LS
authors.lastname: Costa
authors.forename: I P
authors.initials: IP
authors.lastname: Posso
authors.forename: A
authors.initials: A
authors.lastname: Slullitel
mesh_terms: D000701:Analgesics, Opioid / Q000008:administration & dosage*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D008297:Male; D009407:Nerve Block / Q000379:methods*; D010147:Pain Measurement / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D012584:Sciatic Nerve; D014147:Tramadol / Q000008:administration & dosage*
chemical_list: D000701:Analgesics, Opioid; D014147:Tramadol