title: Follow-up of GFR estimated from plasma creatinine after cimetidine administration in patients with diabetes mellitus type 2.
abstract: BACKGROUND
  The glomerular filtration rate (GFR) can be estimated from plasma creatinine according to the formula of Cockcroft and Gault (CG). When tubular secretion of creatinine is inhibited by cimetidine the mean difference between the Cockcroft-Gault clearance (CG(Cim) and GFR approximates zero, but there is still some interindividual difference, especially in type-2-diabetic patients. We studied during longitudinal follow-up, whether the discrepancies between CG(Cim) and GFR per patient are consistent in time in type-2-diabetic patients.
  
  
  METHODS
  In 1996 and 1998 (interval 20-26 months) GFR was measured in 21 patients as the urinary clearance of continuously infused 125I-iothalamate. Plasma creatinine was analyzed with an enzymatic assay before and after oral cimetidine 800 mg t.i.d. during 24 hours. GFR estimations were calculated with the Cockcroft-Gault formula before (CG) and after cimetidine (CG(Cim)) and expressed as means +/- SEM.
  
  
  RESULTS
  GFR deteriorated from 89.7 +/- 5.7 to 81.3 + 5.8 ml/min/1.73 m2 and CG(Cim) from 85.3 +/- 5.7 to 81.1 +/- 6.6 ml/min/1.73 m2, whereas CG decreased from 102.4 +/- 6.8 to 98.4 +/- 7.0 ml/min/1.73 m2. Changes in GFR and changes in CG(Cim) were correlated (r = 0.72, p < 0.001) and were not significantly different from each other. The discrepancy between CG(Cim) and GFR per patient in 1996 also correlated with the discrepancy between CG(Cim) and GFR in 1998 (r = 0.85, p < 0.001 ).
  
  
  CONCLUSIONS
  In individual patients the discrepancies between the CG(Cim) and GFR are consistent in time and the change in GFR is reflected by the change in CG(Cim). This small variability means that CG(Cim), based on an enzymatic plasma creatinine assay, would be suitable for follow-up of GFR in type-2-diabetic patients, independent of albuminuria.
authors.affiliation: Department of Internal Medicine, Internal Medicine of the Academic Medical Centre, University of Amsterdam, The Netherlands.
authors.forename: F A
authors.initials: FA
authors.lastname: Kemperman
authors.forename: J
authors.initials: J
authors.lastname: Silberbusch
authors.forename: E H
authors.initials: EH
authors.lastname: Slaats
authors.forename: A M
authors.initials: AM
authors.lastname: Prins
authors.forename: R T
authors.initials: RT
authors.lastname: Krediet
authors.forename: L
authors.initials: L
authors.lastname: Arisz
mesh_terms: D000328:Adult; D015992:Body Mass Index; D002927:Cimetidine / Q000008:administration & dosage*; D003404:Creatinine / Q000097:blood*; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000188:drug therapy*; D005919:Glomerular Filtration Rate; D006801:Humans; D008297:Male; D008875:Middle Aged
chemical_list: D002927:Cimetidine; D003404:Creatinine