RT Journal Article SR Electronic T1 In vivo disposition of caffeine predicted from hepatic microsomal and hepatocyte data. JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP 349 OP 353 VO 23 IS 3 A1 K A Hayes A1 B Brennan A1 R Chenery A1 J B Houston YR 1995 UL http://dmd.aspetjournals.org/content/23/3/349.abstract AB The kinetics of caffeine metabolism has been investigated in freshly isolated hepatocytes, hepatic microsomes, and in vivo in male Sprague-Dawley rats. A simple Michaelis-Menten model provides an adequate description of each of the three sets of data. There is reasonable agreement between the KM values for the three systems (56-200 microM). Vmax values for hepatocytes and microsomes show good agreement when expressed in the same units using scaling factors for hepatic cellularity and microsomal protein yield [315 and 420 nmol/min/standard rat weight (SRW), respectively]. Both values slightly exceed the in vivo-determined Vmax (190 nmol/min/SRW). Taking the Vmax/KM ratio (intrinsic clearance) as the basis for scaling, the in vitro data from both the hepatocyte (2.6 ml/min/SRW) and microsomal (2.7 ml/min/SRW) studies provide a good prediction of the in vivo total body clearance (3.4 ml/min/SRW).