A simple method for determination of antipyrine clearance

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Abstract
Antipyrine clearance (ClAP) is widely used for assessment of microsomal liver function. The usual procedure involves collection of 4-7 samples of plasma or saliva obtained during 24-48 h. To determine whether this procedure could be simplifed it was compared with one based on a single sample (sClAP) and an estimated volume of distribution (VD) in 142 persons. VD was estimated from body weight in kg (BW), height in centimeters (BH), age in yr and sex, or it was assumed to be 40 l. The agreement between values of ClAP and sClAP increased with the time of the single sample and the 2 clearance estimates were nearly identical in all cases when the sample was taken after 18 h. The method used for assessment of VD had only a small influence on the agreement. Antipyrine clearance (in ml/min) may be estimated as .**GRAPHIC**. where D is the dose of antipyrine (in mg), ct the concentration of antipyrine (in mg/l) at sampling time t (in min), t should be .apprx. 1440 min (24 h), and VD (in l) is calculated as 0.2363 .times. BW + 0.1962 .times. BH - 0.0272 .times. age - 10.26 (women) or 0.3625 .times. BW + 0.2239 .times. BH - 0.1387 .times. age - 14.47 (men). Little information is lost if a fixed volume of 40 l is used. If the dose is 1 g, ct is expressed in mg/l, and the sampling time is 24 h, sClAP = (3.28 - ln ct) .times. 28 ml/min.