SERUM LEVELS OF TACRINE IN RELATION TO CLINICAL-RESPONSE IN ALZHEIMERS-DISEASE

The relationship between the serum concentrations of tacrine (tetrahydroaminoacridine), two of its metabolites and age, sex and therapeutic effect was examined. The improvement in two measures of cognitive function previously reported to show significant changes with the drug (MMSE and AMTS) correlated with blood levels to a modest but significant degree. Age was associated with higher levels of the drug and of its metabolites but there were no differences between males and females on any of the variables examined. The dose required to achieve adequate levels and therapeutic change is estimated to be at least 125 mg of tacrine hydrochloride or 100 mg of the active base. It is suggested that the full therapeutic value of the drug cannot be estimated at doses much below this and that this might explain some of the discrepant results reported in the literature.