Disposition and pharmacokinetics of meptazinol in the CSF. Studies after intrathecal administration in the non-human primate Erythrocebus patas.

A preliminary study is reported on the kinetics of meptazinol following intrathecal and i.m. administration in the Patas monkey. Following intrathecal administration (single dose of 0.5 mg) at T12/L1, meptazinol rapidly disappeared from the CSF with a T1/2 of 35 min. At 240 min after intrathecal injection, most of the meptazinol had been distributed within the spinal tissue near the region of the injection, with minimal amounts reaching the brain (less than 5% of the concentrations present in the lumbar and thoracic tissue). Following i.m. administration (16 mg kg-1) peak concentrations were present in the CSF and plasma within 60 min. Appreciable concentrations persisted in the CSF up to 180 min after i.m. administration. The results would suggest that meptazinol should give rapid but short acting pain relief following intrathecal injection with minimal CNS-related side effects.