title: The effect of liver disease on urine caffeine metabolite ratios.
abstract: OBJECTIVE
  A number of caffeine metabolite ratios (CMRs) have been proposed to measure CYP1A2 activity in vivo. The effect of liver disease on these ratios is not clear. The objective of this study was to determine the influence of liver disease on caffeine metabolite ratios.
  
  
  METHODS
  Two studies were performed. First, in healthy control subjects and in subjects with cirrhosis, caffeine clearance was measured by intravenous infusion of stable isotope-labeled caffeine while subjects consumed oral caffeine. Second, spot urine samples were collected from control subjects and from subjects with either chronic hepatitis or cirrhosis while they consumed caffeine.
  
  
  RESULTS
  In study 1, caffeine clearance was decreased in subjects with cirrhosis (control mean, 0.14 L/hr/kg; cirrhosis mean, 0.04 L/hr/kg; p = 0.003). CMRs were affected by liver disease (e.g., ratio characterizing paraxanthine demethylation [AAMU + 1X + 1U/17U], control median, 8.3; cirrhosis median, 6.2; p = 0.005). AAMU + 1X + 1U/17U correlated significantly with caffeine clearance in the control group (r2 = 0.68; p = 0.0001) and in subjects with cirrhosis (r2 = 0.41; p = 0.05). In study 2, there was a significant difference between control subjects and subjects with cirrhosis for AAMU + 1X + 1U/17U (median for control subjects, 6.2; median for subjects with cirrhosis, 4.3; p = 0.001) but not between control subjects and patients with chronic hepatitis.
  
  
  CONCLUSIONS
  We conclude that AAMU + 1X + 1U/17U is affected by liver disease and reflects the decrease in CYP1A2 activity in subjects with cirrhosis. AAMU + 1X + 1U/17U measured from a spot urine sample reflects caffeine clearance in subjects with cirrhosis and may be useful as a hepatic function test. Despite the large interindividual variation observed, the test can be repeated easily in the same patient and an individual patient's decline in CYP1A2 activity, such as in patients with progressively deteriorating liver function, can be monitored.
authors.affiliation: Division of Clinical Pharmacology and Experimental Therapeutics, San Francisco General Hospital Medical Center, CA 94110, USA.
authors.forename: C P
authors.initials: CP
authors.lastname: Denaro
authors.forename: M
authors.initials: M
authors.lastname: Wilson
authors.forename: P
authors.initials: P
authors.lastname: Jacob
authors.forename: N L
authors.initials: NL
authors.lastname: Benowitz
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D002110:Caffeine / Q000378:metabolism* / Q000493:pharmacokinetics / Q000652:urine; D005260:Female; D006801:Humans; D007262:Infusions, Intravenous; D008103:Liver Cirrhosis / Q000378:metabolism*; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D011517:Prothrombin Time
chemical_list: D002110:Caffeine