The comparability of pharmacokinetics of creatinine in rabbit and man: A mathematical approach

A model simulating the kinetics of creatinine displacement in rabbit is investigated. The model is validated by comparing the predicted renal clearance and production rate constant with observed values and those reported previously in the literature. By applying steady state conditions to the model, a simple equation for prediction of creatinine clearance from serum creatinine is obtained. This is the first equation for predicting clearance which is not based on empirical relationships. The equation is then tested on a set of data from 61 patients with various degrees of renal impairment and a wide variation in weights and ages. It is found that good correlation (r = 0·93) exists between predicted and observed creatinine clearances. This comparability is attributed to the similarities in disposition of a non-threshold substance, like creatinine, in rabbits and man. Thus, it is suggested that more confidence can be placed on the use of rabbit as animal model in creatinine investigations.