Concentration of ondansetron in cerebrospinal fluid following oral dosing in volunteers.

This study measured the concentrations of ondansetron in plasma and cerebrospinal fluid (CSF) in six volunteers after oral dosing to steady state. Ondansetron concentrations ranged from 39.5-147 ng ml-1 in plasma and from 2.6-15.4 ng ml-1 in CSF. There was good correlation between plasma and CSF concentrations (r = 0.89, p = 0.017). CSF concentrations were less than 15% of plasma concentrations in all cases, indicating that the rate of penetration of the blood brain barrier by ondansetron is low.