Oral Bioavailability of Creatine Supplements 2018-06-25T16:24:57+00:00

Oral Bioavailability of Creatine Supplements

Is There Room for Improvement?

Prepared by

Donald W. Miller, Ph.D.
Department of Pharmacology and Therapeutics
University of Manitoba


ISSN & symposium sponsors and organizers
University of Nebraska Medical Center
Dr. Jon Vennerstrom, Dr. Dennis Robinson, Dr. Tom McDonald – University of Manitoba
Nick Miller and Dr. Xiaochen Gu – Vireo Systems


Co-inventor of creatine hydrochloride and other creatine supplement technologies
Member of Scientific Advisory Board for Vireo Systems

Creatine As A Ready Source of High Energy Phosphate

Creatine Sources

To be of benefit, dietary sources of creatine must first be absorbed from the intestine into the bloodstream.

Applications of Creatine Supplements

Athletic performance market- increase power and strength; increase in energy reserve

Muscle recovery- enhanced muscle recovery from injury or workout; reduced soft tissue damage due to intense physical demand

Therapeutic applications

  • Muscle wasting diseases – MD, ALS
  • Neurological conditions – Alzheimer’s, Parkinson’s, mental retardation, stroke, brain trauma
  • Cardiovascular – MI

Concerns with Emerging Indications for Creatine Supplements

Relatively high doses required (5-20 gram/dy)

Inefficient formulations for delivering creatine-side effects including bloating, GI distress, dehydration

Less stringent quality control of product compared to drug or therapeutic agent

Is the standard creatine monohydrate based supplement the best product available for achieving the desired benefits?

General Features of Intestinal Epithelial Cells

Caco-2 Cells as an In Vitro Model for Intestinal Absorption

Immortalized cell line isolated from human colonic carcinoma

Morphological and biochemical properties consistent with intestinal enterocyte (absorptive cell)

Commonly used to assess intestinal absorption of solutes/compounds

Permeability of Creatine Monohydrate Across Caco-2 Monolayers

CRT MONO permeability across intestinal epithelial barrier is relatively low

Journal of Pharmaceutical Sciences vol. 90, page 1593, 2001

Permeability of Creatine Monohydrate Across Caco-2 Monolayers

Mannitol low MW permeability marker used to monitor monolayer integrity

Permeability of 3H-mannitol and 14C-creatine monohydrate is similar in Caco2 monolayers

How can a low permeability agent have complete bioavailability???

Journal of Pharmaceutical Sciences vol. 90, page 1593, 2001

Estimating Oral Bioavailability (%F) Based on In Vitro Indices

Additional Evidence for Incomplete Oral Absorption of CM

Jager et al., J. Intl. Soc. Sports Nutr. 2007

6 subjects given oral dose of CrPyr / Cr C / CrM; 5g molar equivalent
AUC CrPyr = 2985 mM.h
AUC CrM = 2384 mM.h
Significant increase (17%) in bioavailability of CrPyr compared to CrM

Oral Bioavailability of Creatine Supplements: Is There Room for Improvement?

A scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die and a new generation grows up that is familiar with it.

– Max Planck

Factors Influencing Absorption from the GI Tract

Aqueous Solubility – must be in solution to be absorbed

Cell Permeability – measure of how well the compound moves across intestinal barrier

Gastric emptying time

Health / nutritional state of individual

Characteristics of the compound and/or formulation

Can be altered by changing chemistry of the compound

Physiology of the body

Not easily modified

Types of Creatine Supplements

Creatine monohydrate
Creatine pyruvate
Creatine citrate
Creatine hydrochloride
Creatine ethyl ester

Creatine ethyl ester

Within each category potential for multiple formulations- eg microcrystalline creatine monohydrate; effervescent creatine citrate, etc,etc

Wide variety of available creatine supplements

Aqueous Solubility of Creatine Compounds


Summary of Aqueous Solubility Data

Real Lab vs Real-life Solubility

Excess amount of CRT combined with fixed amount of water (RT)
Subject sample to mechanical mixing for 6 hours at room temperature
Take sample, filter, and analyze

Excess amount of CRT combined with fixed amount of water (cold; 4O C)
Subject sample to manual mixing for 20 seconds
Take sample, filter, and analyze

Real world aqueous solubility of various Creatine Supplements

Importance of Aqueous Solubility of Creatine Supplements

Standard dose of creatine supplements range from 5-30 g per day. How much fluid would it take to solubilize the dose?


5g Dose
300 ml / 10 fl oz
625 ml
10g Dose
600 ml / 20 fl oz
1250 ml



5g Dose
7 ml / < 0.25 fl oz
10 ml
10g Dose
14 ml / < 0.5 fl oz
21 ml

Advantages of CRT HCl Salt Form

Less GI distress
Potential for reduced dose
Potential for more efficient formulations for high dose CRT applications

Comparison of Oral Bioavailability of CRT HCl and CRT Mono


10 healthy subjects; each receive CRT Mono and CRT HCl; treatment order was randomly decided; 2 week washout period between treatments

CRT was administered (5 g Dose) with 6 fl. oz. cold water

Blood samples taken at, prior to, and 0.5, 1 and 2 and 3 hours after oral ingestion of creatine

Plasma creatine measured using HPLC

Comparison of plasma Creatine Levels Following Oral Dosing of Creatine Supplement

Comparison of plasma UC for creatine monohydrate and creatine hydrochloride

Oral Bioavailability vs relative bioavailability

FA = AUCoral / AUCiv
RFA = AUCa / AUCb via same administration route

RFA can be used as an index to determine whether improvements in bioavailability actually Occurred between different formulations

Relative Bioavailability of Creatine Hydrochloride Formulation

Relative bioavailability as defined by the FDA:


Bioequivalent dosage forms = 1

Relative Bioavailability of CRT HCl compared to CRT Mono

AUCcc X 4.4
AUCcm X 3.9 = 1.7 + 0.1

Key Study Finding

FDA Bioequivalence demonstrates 70% improved plasma uptake with Creatine HCl compared to Creatine Monohydrate

Study Conclusions

Oral bioavailability of many creatine supplements is relatively low

Likely contributor is the low aqueous solubility of CRT relative to doses used

CRT HCl provides substantial improvement in aqueous solubility over other CRT supplements

CRT HCl has improved oral absorption compared to standard CRT mono formulation

Supplementation with CRT HCl provides a more efficient method for enhancing creatine levels in the body


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