ASSESSMENT OF ANTIPYRINE KINETICS FROM SALIVA OR PLASMA - INFLUENCE OF AGE

The purpose of this study was to investigate whether antipyrine estima tion in saliva provides valid information on plasma antipyrine clearan ce (AP(Cl)) and can be useful as an index of changes in drug metabolis m with age, Antipyrine kinetics was studied in 93 elderly (mean age 82 years) and 23 young (mean age 29 years) volunteers. Plasma antipyrine half-life (APt(1/2)) increased and plasma AP(Cl) declined with age. N o significant difference between plasma- and saliva-derived parameters was found in either young or old subjects, However, the saliva/plasma AC(Cl) ratio tended to increase with age. A highly significant correl ation between saliva and plasma AP(Cl) or APt(1/2) was found in young subjects. Values were less closely related in the elderly and the slop e of the saliva/plasma AP(Cl) relationship was significantly different in both groups of subjects. Residual variance was higher in the regre ssions corresponding to the elderly. The findings in the study indicat e that, the relationship between saliva and plasma kinetics in young s ubjects becomes less reproducible with age.