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Pharmacokinetics of fentanyl following intravenous and transdermal administration in horses
Author(s) -
MAXWELL L. K.,
THOMASY S. M.,
SLOVIS N.,
KOLLIASBAKER C.
Publication year - 2003
Publication title -
equine veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.82
H-Index - 87
eISSN - 2042-3306
pISSN - 0425-1644
DOI - 10.2746/042516403775600415
Subject(s) - transdermal , fentanyl , medicine , pharmacokinetics , administration (probate law) , anesthesia , pharmacology , political science , law
Summary Reasons for performing study : Although fentanyl has been reported to cause CNS excitation in horses, a transdermal therapeutic system (TTS) containing this mu agonist has recently been used empirically in equine medicine to treat moderate to severe pain. A better understanding of the disposition of fentanyl following transdermal administration would facilitate the clinical use of TTS fentanyl to obtain analgesia in horses. Objectives : To determine the pharmacokinetics of fentanyl following i.v. and TTS patch administration in healthy, mature horses and to evaluate the tolerance of horses to TTS fentanyl administration. Methods : The pharmacokinetics of fentanyl in serum were assessed following a single i.v. dose, a single TTS dose, and multiple TTS doses in 6 healthy horses. Physical examinations, haematology and serum biochemistry analyses during transdermal fentanyl application were then performed to determine tolerance of continuous fentanyl administration. Results : Fentanyl was very rapidly and completely absorbed following a single TTS dose. Mean serum fentanyl concentrations consistent with analgesia in other species were reached by 1 h and maintained until 32 h after patch application. Similar steady state serum concentrations were obtained when multiple doses of TTS fentanyl were administered every 48 or 72 h over 8 or 9 days, with less fluctuation in serum concentrations during the 48 h dosing interval. Three horses exhibited brief (<12 h) episodes of increased body temperature; however, transdermal fentanyl administrations were not associated with other significant changes in haematology and biochemistry panels or physical examination findings. Conclusions and potential relevance : Although the pharmacodynamics of fentanyl have not been investigated fully in horses, transdermally‐administered fentanyl exhibited a favourable pharmacokinetic profile without clinically relevant side effects and may be a useful analgesic in equine patients.