Intrathecal ketamine with preservative - histological effects on spinal nerve roots of baboons

Ketamine, an analgesic-cataleptic drug, provides pain relief without respiratory depression. Ketamine with the preservative benzethonium chloride 0.1 mg/ml was injected intrathecally into 4 baboons under Ketamine anaesthesia. A control group of 2 baboons received intrathecal saline. No assessment as to relief from experimental pain was possible, but all the baboons recovered normally from anaesthesia and were found moving about in their enclosures without gross evidence of neurological impairment. No adverse reactions were noted. One month after the intrathecal injection the baboons were sacrificed, and an autopsy was performed within 30 minutes. No macroscopic abnormally of the cord was noticed. Microscopic examination revealed oedema of a few nerve roots in all animals irrespective of whether ketamine or saline had been injected intrathecally. No other changes attributable to ketamine were seen, and its is therefore concluded that, in the doses given, intrathecally injected ketamine would seem to be safe.