Comparative analgesic and sedative effects of tramadol, tramadol-lidocaine and lidocaine for caudal epidural analgesia in donkeys (Equus asinus).

OBJECTIVE

To compare anti-nociceptive and sedative effects of tramadol, a combination of tramadol-lidocaine, and lidocaine alone for perineal analgesia in donkeys.

STUDY

DESIGN

Experimental 'blinded' randomized cross-over study.

ANIMALS: Six healthy adult donkeys.

METHODS

Treatments were tramadol (TR) (1.0 mg kg(-1) ), tramadol-lidocaine (TRLD) (0.5 and 0.2 mg kg(-1) respectively) and lidocaine (LD) (0.4 mg kg(-1) ) given into the epidural space. The volume of all treatments was 0.02 mL kg(-1) . Nociception was tested at the perineal region by pin prick, followed, if no reaction, by pressure from a haemostat clamp. Times to onset, degree and duration of anti-nociception of the perineal region were recorded. Response was tested immediately after drug administration and at: 2, 5, 10, 15, 30, 45, and 60 minutes post-administration and then at 30 minute intervals thereafter until a response re-occurred. Physiologic data and degree of sedation and ataxia were recorded pre-administration and at intervals for 240 minutes post-administration. Results were analyzed using anova, Kruskal-Wallis tests, and Wilks' Lambda test as relevant. Significance was taken as p < 0.05.

RESULTS

Times (minutes, mean ± SD) to onset and duration of anti-nociception, respectively were; TR 13 ± 1.6 and 220 ± 4.6; TRLD 6 ± 0.8 and 180 ± 8.5; LD 4 ± 1.4 and 75 ± 4. Onset and duration times were significantly longer with TR than the other two treatments. TR never produced complete anti-nociception, whereas the TRLD and LD induced complete anti-nociceptive effects. Duration was significantly longer with TRLD than with LD alone. Epidural injections of TR and TRLD induced mild sedation.

CONCLUSIONS AND CLINICAL RELEVANCE: Epidural combination of TRLD produced an anti-nociceptive effect in the perineum, which was rapid in onset and had a longer duration of action than LD alone. An epidural single dose of TRLD combination would appear to provide an acceptable analgesic effect in the perineal region of donkeys.