Effect of fentanyl on thermal and mechanical nociceptive thresholds in horses and estimation of anti-nociceptive plasma concentration

Publication date: Available online 31 May 2019Source: The Veterinary JournalAuthor(s): J. Echelmeyer, P.M. Taylor, K. Hopster, K. Rohn, J. Delarocque, S.B.R. KästnerAbstractThere are few investigations relating anti-nociception to plasma concentrations of fentanyl in horses. The study objective was to evaluate analgesic efficacy and duration in horses and determine the minimum anti-nociceptive plasma concentrations. Eight horses were treated with saline (P) and fentanyl (F2.5 = 2.5 µg/kg; F5 = 5 µg/kg; F10 = 10 µg/kg) given IV over 5 min, with a wash-out period of 10 days. To evaluate thermal (°C) and mechanical (N) nociceptive threshold single stimulations were applied prior to (baseline) and 10, 30, 60, 90, 120, 180, 240, 300, 360, 420, 540 min and 22.5 h after treatment. Plasma fentanyl concentrations were measured at specific time points. Locomotor activity, heart rate, respiratory rate and gastrointestinal sounds were recorded. Two-way repeated measures ANOVA and pairwise comparisons were used for data analysis (P < 0.05).With treatment F10, there was a significant increase in thermal threshold above baseline (47.2 ± 4.1 °C) at t10 (53.7 ± 4.2 °C) and t30 (52.1 ± 5.6 °C), whereas mechanical threshold increased considerably above baseline (3.7 ± 1.3 N) only at t10 (6.6 ± 3.6 N). Estimated mean minimum anti-nociceptive plasma concentration determined by thermal stimulation was 6.1–6.8 ng/mL. Dos...
Source: The Veterinary Journal - Category: Veterinary Research Source Type: research