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Pharmacokinetics and pharmacodynamics of meperidine after intramuscular and subcutaneous administration in horses
Author(s) -
Hanafi Amanda L.,
Reed Rachel A.,
Trenholme Heather N.,
Sakai Daniel M.,
Ryan Clare A.,
Barletta Michele,
Quandt Jane E.,
Knych Heather K.
Publication year - 2021
Publication title -
veterinary surgery
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.652
H-Index - 79
eISSN - 1532-950X
pISSN - 0161-3499
DOI - 10.1111/vsu.13545
Subject(s) - medicine , pharmacodynamics , saline , crossover study , pharmacokinetics , anesthesia , respiratory rate , heart rate , pharmacology , alternative medicine , pathology , placebo , blood pressure
Objective To describe the pharmacokinetics and pharmacodynamics of meperidine after IM and subcutaneous administration in horses. Study design prospective, randomized, blinded, crossover trial. Animals Six adult horses weighing 494 ± 33 kg. Methods Treatments included meperidine 1 mg/kg IM with saline 6 mL subcutaneously, meperidine 1 mg/kg subcutaneously with saline 6 mL IM, and saline 6 mL subcutaneously and 6 mL IM, with a 7‐day washout between treatments. Plasma meperidine concentrations and pharmacodynamic values (thermal and mechanical thresholds, physiological variables, fecal production) were collected at various time points for 24 hours. Accelerometry data were obtained for 8 hours to measure locomotor activity. Data were analyzed with a mixed effects model, and α was set at .05. Results Meperidine terminal half‐life (T 1/2 ), maximal plasma concentrations, and time to maximal concentration were 186 ± 59 and 164 ± 56 minutes, 265.7 ± 47.2 and 243.1 ± 80.1 ng/mL at 17 ± 6, and 24 ± 13 minutes for IM at subcutaneous administration, respectively. No effect of treatment or time was observed on thermal or mechanical thresholds, heart rate, respiratory rate, locomotor activity, frequency of defecations, or fecal weight ( P > .2 for all). Conclusion Maximum meperidine concentrations were achieved quickly with a short T 1/2 in both treatment groups. Neither IM nor subcutaneous meperidine influenced thermal or mechanical threshold or physiological variables. Clinical significance The short half‐life and lack of detectable antinociceptive effect do not support IM or subcutaneous administration meperidine at 1 mg/kg for analgesia in horses.