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Relationship between plasma concentrations and analgesia after intravenous fentanyl and disposition after other routes of administration in cats 1
Author(s) -
ROBERTSON S. A.,
TAYLOR P. M.,
SEAR J. W.,
KEUHNEL G.
Publication year - 2005
Publication title -
journal of veterinary pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.527
H-Index - 60
eISSN - 1365-2885
pISSN - 0140-7783
DOI - 10.1111/j.1365-2885.2004.00628.x
Subject(s) - fentanyl , pharmacokinetics , cats , saline , anesthesia , plasma concentration , dosing , nasal administration , chemistry , pharmacodynamics , pharmacology , crossover study , medicine , alternative medicine , pathology , placebo
Data allowing rational use of analgesics in cats are limited. Pharmacokinetics and pharmacodynamics of fentanyl were studied in cats. Plasma fentanyl concentrations were measured using radioimmunoassay in a crossover study in six cats after 10 μ g/kg (i.v.) or by application of fentanyl in pluronic lecithin organogel (PLO) to the inner ear pinna. On a separate occasion thermal thresholds were measured after i.v. fentanyl (10 μ g/kg) or saline. Plasma fentanyl concentrations reached 4.7–8.31 ng/mL 2 min after i.v. administration and were undetectable after 95 min. Fentanyl was not detected in plasma at any time after PLO use. Thermal thresholds did not change following saline administration but were increased above baseline from 5 to 110 min after i.v. fentanyl. In this model a plasma concentration of >1.07 ng/mL was required to provide analgesia. Plasma concentrations were measured in additional cats after intranasal or oral dosing (2 μ g/kg) and after 30 μ g/kg in PLO gel. After oral and nasal dosing, C max values were 0.96 and 1.48 ng/mL at 5 and 2 min, respectively. Plasma fentanyl was not detected after application of the higher dose of fentanyl in PLO.