N-Acetylcysteine does not artifactually lower plasma creatinine concentration.
BACKGROUND
All randomized controlled trials of N-acetylcysteine (NAC) in contrast media-induced nephropathy used creatinine as a marker of renal function. However, it has been suggested that NAC may lower plasma creatinine levels independent of any effects on glomerular filtration rate (GFR).


METHODS
At a tertiary hospital 110 cardiac surgical patients were randomly allocated to peri-operative infusion of NAC (300 mg/kg over 24 h, N = 30) or placebo (N = 80). We compared the plasma concentrations of creatinine, cystatin C and urea, the plasma creatinine/plasma cystatin C ratio and the estimated GFR at baseline and at 24 and 72 h after commencement of the infusion. We measured urinary creatinine concentration at 24 h.


RESULTS
At baseline, the plasma creatinine/plasma cystatin C ratio did not differ between the NAC and placebo group (0.90 versus 0.92; P = 0.94). There was no significant difference in the plasma creatinine/plasma cystatin C ratio for the NAC and placebo group either during or after NAC infusion at 24 h (1.03 versus 1.00; P = 0.78) and 72 h (0.94 versus 0.89; P = 0.09). Those allocated to NAC showed no difference in urinary creatinine excretion when compared to placebo (P = 0.24).


CONCLUSIONS
The results of our study do not demonstrate that NAC artifactually lowers creatinine measured using the Jaffé method. (ClinicalTrials.gov, NCT00332631, NCT00334191).
Haase
Michael
M
Director of Intensive Care Research, Austin Hospital, University of Melbourne, 3084 Heidelberg, Victoria, Australia.
Haase-Fielitz
Anja
A
Ratnaike
Sujiva
S
Reade
Michael C
MC
Bagshaw
Sean M
SM
Morgera
Stanislao
S
Dragun
Duska
D
Bellomo
Rinaldo
R
D000111:Acetylcysteine / Q000008:administration & dosage / Q000494:pharmacology*; D000368:Aged; D006348:Cardiac Surgical Procedures; D003287:Contrast Media / Q000009:adverse effects; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C; D015891:Cystatins / Q000097:blood; D004311:Double-Blind Method; D005260:Female; D005919:Glomerular Filtration Rate / Q000187:drug effects; D006801:Humans; D007262:Infusions, Intravenous; D007430:Intraoperative Care; D007674:Kidney Diseases / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D014508:Urea / Q000097:blood
C525030:CST3 protein, human; D003287:Contrast Media; D055316:Cystatin C; D015891:Cystatins; D014508:Urea; D003404:Creatinine; D000111:Acetylcysteine