Effect of Creatine on Serum and Urine Creatinine (ECSUC)

Background: Creatinine (Crn) concentration is used to assess renal function via calculation of GFR (Glomerular Filtration Rate). By RIFLE (Risk, Injury, Failure, Loss, End Stage Kidney Disease) criteria, acute kidney injury (AKI) and acute renal failure (ARF) are defined by a two-fold and three-fold increase in serum Crn, respectively. Crn is a breakdown product of proteins and circulating creatine, and it is generally a benign product present in serum. Creatine is a nutritional supplement that has been available since 1993, and it is widely used among athletes today. Methods: In an IRB approved, blinded crossover trial, 25 human volunteers ingested 2 creatine supplements to determine any associated statistically significant increase in serum Crn and clinically significant increase in serum Crn to a degree associated with AKI or ARF. Urine samples were also collected to examine excretion patterns after an ingested sample. Participants ingested 10 gm of creatine ethyl ester (CEE) or creatine monohydrate (CrM) and had serum Crn assayed at 0, 1, 2, 3, 4, 5 and 24 hours. Urinary Crn levels were assayed at 0, 1.5, 3, 5 and 24 hours. Exclusion factors were any history of renal disease or use of creatine within the last month. Statistical analysis was performed by Wilcoxon Matched-Pair Signed Ranks Test and descriptive summary statistics were performed.

Creatine, Creatinine, Serum Creatinine, Urine Creatinine, Creatine Monohydrate, Creatine Ethyl Ester, Acute Kidney Injury, Renal, Kidney

GNC Pro Performance Fruit Punch Creatine Monohydrate, Tang brand Orange Drink, manufactured by Kraft Foods

Each subject ingested 10 grams of commercially available creatine monohydrate orally. This was equivalent to two teaspoons according to the manufacturer's recommendations. The creatine was then solubilized in 8 oz. of water and 2 tablespoons of Tang brand orange flavored drink mix.

Each subject ingested 10 grams of creatine ethyl ester orally. This was equivalent to 14.25 pills according to the manufacturer's ingredient description. The pill capsules were ground into a powder, which was added to 8 oz of water along with 2 tablespoons of Tang brand orange drink.

Participants ingested 10 grams of creatine monohydrate or creatine ester and had serum creatinine measured at 0, 1, 2, 3, 4, 5, and 24 hours.

Participants ingested 10 grams of creatine monohydrate or creatine ethyl ester and had urinary creatinine levels measured at 0, 1.5, 3, 5, and 24 hours.

Inclusion Criteria: Age over 18 Human Exclusion Criteria: Use of any form of creatine within 4 weeks prior to participation in study. Pregnancy History of elevated creatinine or renal insufficiency History of PKU