[Pharmacokinetics of paracetamol in the cerebrospinal fluid in the elderly]

We investigated acetaminophen pharmacokinetics in CSF in twelve operated arteritics patients with continuous spinal anesthesia. Nine men and three women aged 77 +/- 7 years and weighing 66 +/- 15 kg entered in the study after expressing verbal informed consent. They received intravenously a single dose of acetominophen (equivalent to 1 g). Fifteen minutes to six hours after the intravenous injection, blood and CSF samples were withdrawn every thirty minutes, except during the second to the third hour were it was every fifteen minutes. Acetaminophen concentrations in blood and in CSF were assayed by HPLC. Acetaminophen was detected in the earliest samples (1.32 +/- 1.32 micrograms.ml-1) and then increased up to 8.16 +/- 3.04 micrograms.ml-1 at 186 +/- 56 minutes. From 135th to 345th minute, acetaminophen concentration in CSF stay at about 6 micrograms.ml-1, which is the duration of its maximal analgesic central effect.