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COMPARISON OF THE ACTIONS OF CENTRALLY AND PERIPHERALLY ADMINISTERED CLONIDINE AND GUANFACINE IN THE RABBIT: INVESTIGATION OF THE DIFFERENCES
Author(s) -
BARBER N.D.,
REID J.L.
Publication year - 1982
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1982.tb09342.x
Subject(s) - guanfacine , clonidine , endocrinology , chemistry , anesthesia , medicine
1 Guanfacine was administered intravenously to rabbits and produced a dose‐dependent lowering of blood pressure. 2 Clonidine and guanfacine, administered to rabbits intravenously (30 μg/kg and 300 μg/kg respectively) and intracisternally (3 μg/kg and 12 μg/kg respectively) caused a similar degree of hypotension, apparently of central origin. 3 Saliva flow in vivo was estimated. Clonidine (30 μg/kg, i.v.) caused a significant decrease in salivation ( P <0.05) for the first 50 min after injection. Guanfacine caused a significant fall ( P <0.05) only at 50 and 180 min after injection. 4 Apparent partition coefficients for an octanol/buffer system at pH 7.4 for clonidine and guanfacine were 5.4 and 21.2 respectively. 5 Measurement of guanfacine levels concurrently in both plasma and brain showed that guanfacine had higher brain than plasma levels and that the brain levels were fairly constant over the 3 h measured. Brain:plasma ratios were 2.1:1, 5.3:1 and 13.6:1 after 15, 90 and 180 min respectively. 6 These results suggest that the long duration of action of guanfacine is due to its persistence at its central site of action.