The antinociceptive effects of a high-concentration formulation of buprenorphine alone or followed by hydromorphone in conscious cats

Abstract Objective To evaluate the thermal antinociceptive effects of a high-concentration formulation of buprenorphine alone or followed by hydromorphone in conscious cats. Study design Randomized, blinded, placebo-controlled crossover study design. Animals A total of six purpose-bred, adult female ovariohysterectomized Domestic Short Hair cats. Methods Cats were allocated into three treatments each consisting of two injections, subcutaneous then intravenous (IV) administration, 2 hours apart: treatment SS, two injections of 0.9% saline; treatment BS, buprenorphine (0.24 mg kg−1, 1.8 mg mL−1) and saline; and treatment BH, buprenorphine (0.24 mg kg−1) and hydromorphone (0.1 mg kg−1). Skin temperature (ST) and thermal threshold (TT) were recorded before (baseline) and for 24 hours following first injection. TT data were analyzed using mixed linear models and a Benjamini–Hochberg sequential adjustment procedure (p Results There were no significant differences among treatments for baseline ST and TT values, SS over time and between BS and BH. When compared with baseline, TT was significantly increased at all time points in BH and BS except at 2 hours in BS. When compared with SS, TT was significantly higher at 3–18 hours for BS and 4–12 hours for BH. Maximal increases in TT were 47.5 °C at 2 hours in SS, 53.9 °C at 3 hours in BS and 52.4 °C at 6 hours in BH. Conclusions and clinical relevance Administration of IV hydromorphone following high-concentration buprenorphine provided no additional antinociception and decreased the duration of effect when compared with high-concentration buprenorphine alone. Alternative analgesics should be considered if additional analgesia is required after administration of high-concentration buprenorphine.