Discrepancy between the development of tolerance to bupivacaine in extradural and spinal anaesthesia in rabbits.
We gave equal groups of rabbits seven extradural (500 micrograms kg-1) or intrathecal (250 micrograms kg-1) injections of bupivacaine, at 24-h intervals. A decrease in the duration of motor block was observed after the extradural injections. The intrathecal injections exerted a reproducible effect. An additional regimen was tested in which five doses of bupivacaine 125 micrograms kg-1 were administered intrathecally after a loading dose of 250 micrograms kg-1, when the animals showed partial recovery from the previous dose; there was no decrease in the effect. The absence of tolerance to intrathecal bupivacaine implies that tachyphylaxis to extradural local anaesthetics results from a decrease in availability of the drug to the neural target, rather than a diminution in effect at the site of action.
Kaplan Hospital, Rehovot, Israel.
E
E
Golomb
L
L
Langerman
S
S
Benita
D000767:Anesthesia, Epidural; D000775:Anesthesia, Spinal; D000818:Animals; D002045:Bupivacaine; D004361:Drug Tolerance; D008297:Male; D009046:Motor Neurons / Q000187:drug effects; D009407:Nerve Block; D011817:Rabbits; D013997:Time Factors
D002045:Bupivacaine