Objective: The plasma and cerebrospinal fluid (CSF) disposition of yohimbine (YO) and 11-hydroxy-yohimbine (11-OH-YO), after oral administration of a single dose of YO (0.65 mg.kg-1) were studied in young and older healthy subjects and in patients with Alzheimer's disease (AD).
Results: Plasma disposition of YO displayed large variability; no significant differences among subject groups were observed. In contrast, 11-OH-YO Cmax and AUC were significantly lower in the older normal subjects than in the young normal or AD subjects. A strong positive correlation between CSF and plasma YO concentrations was observed. A weak positive correlation between CSF and plasma concentrations of 11-OH-YO was also observed. CSF to plasma concentration ratios for yohimbine and 11-OH-YO were low (approximately 2%).