Disposition, behavioural and physiological effects of escalating doses of intravenously administered fentanyl to young foals

作者：Knych H K^*; Steffey E P; Ca**eer H C; Mitchell M M

来源：Equine Veterinary Journal, 2015, 47(5): 592-598.

DOI：10.1111/evj.12318

• horse
• analgesic
• fentanyl
• foals
• opioid

Reasons for performing studyFoal responses to a broader range of plasma fentanyl concentrations than currently reported are desirable to support (or not) clinical use.
ObjectivesTo describe fentanyl plasma concentrations following an escalating i.v. fentanyl dosing schedule in foals aged 5-13 days and describe selected, associated dose- and time-related behavioural and physiological responses to plasma fentanyl concentration.
Study designExperimental.
MethodsFentanyl was administered i.v. in an escalating fashion (2, 4, 8, 16 and 32g/kg bwt) at 10-min intervals. Blood samples were collected before and at selected times until 24h post administration. Blood samples were analysed for fentanyl and metabolite concentrations and correlated with behavioural and physiological observations and selected blood analytes.
ResultsFoals mostly appeared to be unaffected following 2g/kg bwt (1.09 0.41g/l; average maximal plasma concentration) of fentanyl, but 6 of the 8 foals appeared to be sedated following 4g/kg bwt (3.07 +/- 1.11g/l). Ataxia with increased locomotor activity, muscle rigidity and head pressing posture was observed in many foals at 8 (7.24 +/- 3.22g/l) and 16g/kg bwt (17.4 +/- 5.67g/l). All foals were heavily sedated after 32g/kg bwt (34.5 +/- 10.3g/l); 3 of the 8 foals became recumbent. The average (+/- s.d.) terminal half-life following administration of the final dose was 44.2 +/- 9.85min.
ConclusionsBehavioural and physiological responses to i.v. fentanyl in young foals are dose related. As with mature horses, the window of fentanyl plasma concentrations related to possible clinically desirable actions appears relatively narrow.

• 出版日期2015-9