Thermal antinociceptive effect of transdermal tramadol hydrochloride in avian

Drug administration in avian species via the parenteral route tends to result in stress, as most often birds need to be handled and manipulated. The purpose of this study was to evaluate the potential of the transdermal administration route as an alternative for tramadol hydrochloride in avian. A total of 24 85-day-old broiler chickens were used as a model for avian species in this study. The chickens were divided into four equal groups of 6 animals each: i. Control, without intervention (C); ii. Intravenous at 5 mg/kg (IV); iii. Transdermal at 5 mg/kg (TD1); and iv. Transdermal at 10 mg/kg (TD2). The thermal antinociception effect was opted to simulate pain, by using a heating plate. The foot withdrawal response of each animal to a thermal stimulus was determined pre-administration (as baseline), followed by 30-, 60-, 120-, 240-, 360- and 480-min post-tramadol administration. All treatment groups showed significantly higher (P<0.05) foot withdrawal temperature threshold compared to the control group. Comparatively, there was a statistically significant higher temperature threshold than baseline at 60-, and 120-min post treatment for both TD1 and TD2 groups, while the IV group only at 60-min post treatment. Intravenous tramadol recorded the highest change in the foot withdrawal thermal threshold, while transdermal tramadol at 10 mg/kg recorded the longest effective time up to 240 min post-administration. This is the first study to evaluate the analgesic effectiveness of transdermal tramadol in avian, thus further investigation is required to confirm similar effects in other species.