Antipyrine clearance in children from single saliva samples.

The saliva clearance of antipyrine was measured in 18 children from four samples taken about 9, 13, 22 and 25 h after ingestion of 20 mg kg-1. Antipyrine clearance determined from each of the samples using a volume of distribution estimated from age (A) and body weight (BW) and height (BH) (V = 1.535 X A + 0.339 X BW + 0.300 X BH - 35.63 (1] correlated closely with clearance determined from the total elimination curve (r greater than 0.94). Random variation and systematic deviation were minimal when the 22 h sample was used for clearance determination (r = 0.98, P less than 0.001, regression curve slope = 1.00, intercept = 0.58 and residual variance = 4.02). The one-sample method for determination of antipyrine saliva clearance is non-invasive, easy to perform and acceptable to children.