IngredientsEthyl-Alpha-Guanido-Methyl-Ethanoate is the systematic IUPAC-style chemical name for the compound more widely recognised in the scientific and sports-nutrition literature as creatine ethyl ester (abbreviated CEE). It is better known as creatine ethyl ester, a modified form of creatine. The compound is also referred to in research literature by the contracted name AlphaGEE (from Ethyl-α(guanido-methyl)ethanoate), and occasionally written as ethyl (α-guanido-methyl) ethanoate in patent filings.
CAS number: 15366-29-7.
Creatine ethyl ester is a synthetic prodrug derivative of creatine. Creatine ethyl ester hydrochloride (CEE) was synthesised as a prodrug of creatine (CRT) to improve aqueous solubility, gastrointestinal permeability, and ultimately the pharmacodynamics of CRT. The parent molecule, creatine (N-[aminoiminomethyl]-N-methyl glycine), is an amino acid–like compound that is produced endogenously in the liver, kidney, pancreas, and possibly the brain from the biosynthesis of the essential amino acids methionine, glycine, and arginine, or obtained from dietary sources.
The molecular structure of creatine consists of a negatively charged carboxyl group and a positively charged functional group. Creatine is a polar molecule and hydrophilic due to this composition, which limits creatine bioavailability. In creatine ethyl ester, an ethyl group is esterified to the carboxyl moiety of creatine, which was hypothesised to increase lipophilicity and thereby improve passive diffusion across membranes. Esterification is a process widely used by pharmaceutical companies to increase bioavailability of certain prescription drugs with low bioavailability. In a continued attempt to more effectively increase intramuscular creatine levels, one of the latest creatine variations is creatine ethyl ester.
Other marketed forms of CEE include creatine methyl ester hydrochloride, di-acetyl creatine ethyl ester, creatine ethyl ester pyruvate, creatine ethyl ester malate, and creatylglycine ethyl ester fumarate. CEE is commercially available as capsules, tablets, and loose powders, frequently in combination with other sports-nutrition ingredients.
Creatine ethyl ester does not occur naturally in food or in the human body; it is a laboratory-synthesised compound. Its parent molecule, creatine, is, however, ubiquitous in biology. The primary dietary sources are high-protein foods including meat, fish, and poultry. The amount of creatine across natural food sources varies from 0.2 g/kg in breast milk to 11.0 g/kg in raw and dried herring fillet; plant-based foods do not contain any creatine.
Although the human body produces a portion of its daily creatine needs, approximately 50% must be obtained through the diet — predominantly from animal-based foods like red meat and fish. Creatine synthesis requires three amino acids: glycine, methionine and arginine, and three enzymes: L-arginine:glycine amidinotransferase (AGAT), methionine adenosyltransferase (MAT) and guanidinoacetate methyltransferase (GAMT). The entire glycine molecule is consumed in creatine synthesis but only the methyl and amidino groups, respectively, from methionine and arginine.
Creatinine loss averages approximately 2 g (14.6 mmol) for 70 kg males in the 20- to 39-year age group. Creatinine loss is lower in females and in older age groups because of lower muscle mass. Approximately half of this creatine lost to creatinine can be replaced, in omnivorous individuals, by dietary creatine. However, since dietary creatine is only provided in animal products, principally in meat and fish, virtually all of the creatine loss in vegetarians must be replaced via endogenous synthesis.
About 65% of creatine is stored in the musculature of mammals in the form of phosphocreatine (creatine bound to a phosphate molecule), and utilised mostly as a source of energy for muscle. The balance is stored in other tissues. Once synthesised or ingested, creatine is transferred from the plasma through the intestinal wall into other tissues by specific creatine transporters located in skeletal muscles, the kidney, heart, liver, and brain.
Creatine itself was first isolated from skeletal muscle in 1832 by the French chemist Michel Eugène Chevreul, and its systematic study intensified after the demonstration of its ergogenic properties in the early 1990s. Creatine ethyl ester, as a synthetic derivative, has no documented traditional or pre-modern use in any culture or ethnobotanical tradition; it is entirely a product of late-twentieth and early twenty-first century nutritional biochemistry. Esterification is a process widely used by pharmaceutical companies to increase bioavailability of certain prescription drugs with low bioavailability. The application of this pharmaceutical technique to creatine was first documented in peer-reviewed chemistry literature in the mid-twentieth century; Dox and Yoder published work on the esterification of creatine in the Journal of Biological Chemistry in 1922. Further foundational work was published when Mold, Gore, Lynch, and Schantz described creatine ethyl ester in the Journal of the American Chemical Society in 1955.
Commercial dietary supplement interest in CEE emerged in the early 2000s, when supplement manufacturers began marketing it as an improved-absorption alternative to creatine monohydrate. Manufacturers of creatine ethyl ester claimed it to be superior to other forms of creatine, but there was no published scientific evidence to substantiate these claims. It remains in commercial distribution today, although its market share is considerably smaller than that of creatine monohydrate.
Unlike botanical supplements, creatine ethyl ester is a single defined synthetic molecule rather than a complex mixture of phytochemicals. Its pharmacological activity depends primarily on its relationship to three chemical entities:
Creatine functions as an energy buffer, facilitating the rapid regeneration of ATP in tissues with high metabolic demands such as skeletal muscle, brain and heart. Oral supplementation of creatine has been shown to increase creatine concentration in muscle, and also enables an increase in the resynthesis of phosphocreatine, resulting in a rapid replenishment of ATP within the first two minutes of the start of exercise. Multiple high-quality studies and systematic reviews have demonstrated that creatine supplementation increases intramuscular phosphocreatine stores, enabling greater adenosine triphosphate (ATP) regeneration during high-intensity, short-duration exercises such as weight lifting and sprinting.
Creatine ethyl ester was developed to potentially enhance the absorption and bioavailability of creatine compared to the standard creatine monohydrate form. The rationale was that replacing the hydrophilic carboxylate with a lipophilic ethyl ester group would reduce polarity and increase passive membrane transport, allowing more creatine to reach skeletal muscle without requiring the saturable creatine transporter (CrT). However, as detailed in Section 5, this proposed advantage has not been supported by in-vivo human data.
A separate line of research has investigated CEE and related creatine derivatives for direct anti-inflammatory activity, independent of the ATP-buffering role. One published PMC study examined the anti-inflammatory effects of several different dietary supplements in cultured canine chondrocytes (CnCs) as an in-vitro model of osteoarthritis (OA). The dietary supplements examined included creatine monohydrate (CM), creatine hydrochloride (CHCl), glucosamine sulphate (GS), and the conjugated amino acid supplement Ethyl-α(guanido-methyl)ethanoate (AlphaGEE). Creatinine (CRN), a stable metabolite of creatine, was also examined. Effects on traditional inflammatory mediators, such as prostaglandin E2 (PGE2) and TNFα, were evaluated along with a more extended oxylipin analysis.
While all the dietary supplements examined were able to inhibit the release of PGE2, AlphaGEE was the most potent, with significant effects on PGE2 and TNFα release observed at 10 μM. Of the dietary supplements examined, AlphaGEE appeared to be the most efficacious and potent at reducing PGE2 release from CnCs, with responses observed at concentrations as low as 10 μM and maximal inhibition of 76% at the 8-hour time point.
CEE also exhibits a distinctive immunological profile compared with its parent compound. Using Real-time PCR, researchers examined the impact of short-term exposure of a mouse macrophage cell line (RAW 264.7 cells) to creatine monohydrate (CR) and creatine ethyl ester (CEE) as well as creatinine (CRN), on expression of toll-like receptor-2 (TLR-2), TLR-3, TLR-4, and TLR-7. CR down-regulated TLR-2, TLR-3, TLR-4 and TLR-7 mRNA levels in RAW cells. Similar results were observed following exposure of RAW cells to CRN. Conversely, CEE appears to possess immunostimulatory properties and increases expression of TLR-2, TLR-3, TLR-4, and TLR-7 in RAW cells. This finding — that CEE behaves in a direction opposite to creatine monohydrate with respect to TLR modulation — is notable and merits further investigation; it remains confined to in-vitro data.
The in-vivo fate of orally ingested CEE is largely determined by pH-dependent chemical stability. CEE was synthesised as a prodrug of creatine to improve aqueous solubility, gastrointestinal permeability, and ultimately the pharmacodynamics of creatine. HPLC and proton NMR characterisation of the pH-dependent stability of CEE in aqueous solution revealed that CEE was most stable in strongly acidic conditions (half-life = 570 hours at pH 1.0) where it undergoes ester hydrolysis to CRT and ethanol. At pH ≥ 1.0, CEE cyclises to CRN with the logarithm of the first-order rate constant increasing linearly with pH. Above pH 8.0 (half-life = 23 seconds) the rate of degradation was too rapid to be determined.
Research reported that CEE converted to creatinine in a linear manner as pH levels dropped below 8.0 and that CEE was mostly stable at a pH of 1.0. Since acidity in the stomach generally ranges from 1.5 to 3.5, it is likely that some CEE is degraded into creatinine during normal digestion while delivering some level of creatine to blood.
Esterified creatine is unstable in low-pH conditions, and has been shown to be rapidly degraded to creatinine in stomach acid. This GI degradation to the biologically inert waste product creatinine substantially limits the proportion of intact CEE — or the creatine released from hydrolysis of CEE — that reaches skeletal muscle, compared with the near-complete bioavailability of creatine monohydrate. Studies have shown that creatine monohydrate (CrM) is characterised by almost 100% bioavailability, is not degraded to creatinine in the gastrointestinal tract, and effectively increases creatine concentration in plasma and in target tissues such as muscle and brain.
Study type and population: A seven-week supplementation regimen combined with resistance training examined the effects of CEE on body composition, muscle mass, muscle strength and power, serum and muscle creatine levels, and serum creatinine levels in 30 non-resistance-trained males. In a double-blind manner, participants were randomly assigned to a maltodextrose placebo (PLA), creatine monohydrate (CRT), or creatine ethyl ester (CEE) group. This study, published in the Journal of the International Society of Sports Nutrition (2009), is the primary head-to-head controlled clinical trial of CEE versus creatine monohydrate.
Primary outcomes: Total muscle creatine content was significantly higher in the CRT group (p = 0.026) and CEE group (p = 0.041) compared to PLA, with no differences between CRT and CEE on this measure. Significant changes over time were observed for body composition, body water, muscle strength and power variables, but no significant differences were observed between groups. In conclusion, when compared to creatine monohydrate, creatine ethyl ester was not as effective at increasing serum and muscle creatine levels or in improving body composition, muscle mass, strength, and power. Therefore, the improvements in these variables can most likely be attributed to the training protocol itself, rather than the supplementation regimen.
Serum creatinine finding: Researchers found that serum creatinine levels were significantly increased in the CEE group after 6, 27, and 48 days of supplementation, indicating less efficient bioavailability. In addition, while CEE supplementation promoted a modest increase in muscle total creatine content, it was increased to a greater extent in the CM group.
Evidence strength: The single randomised, double-blind trial is adequately powered for short-term comparisons but limited in duration (seven weeks) and population (young non-resistance-trained males only). Since there is some evidence that ingesting high doses of CEE can increase muscle creatine content and performance compared to placebo, CEE has been categorised in the "some evidence" category. However, additional research is recommended to evaluate safety given the increased creatinine levels observed. The ISSN position stand concluded that claims that different forms of creatine are degraded to a lesser degree than creatine monohydrate in vivo, or result in a greater uptake to muscle, are currently unfounded. Clinical evidence has not demonstrated that different forms of creatine such as creatine citrate, creatine serum, or creatine ethyl ester confer advantages over creatine monohydrate.
In-vitro evidence: The canine chondrocyte study described above (PMC6587887) constitutes the primary peer-reviewed in-vitro data on AlphaGEE/CEE as an anti-inflammatory agent in joint disease. The results demonstrate that inflammatory processes within chondrocytes can be modified by treatment with selected amino acids and GS and suggest that further studies with these nutraceuticals as potential alternative or complementary treatments for OA are warranted.
Patent-level evidence: A US patent application (US20150164847A1) describes a method and composition for treating osteoarthritis including administering an anti-inflammatory agent to a patient, wherein the anti-inflammatory agent is ethyl (α-guanido-methyl) ethanoate. Ethyl (α-guanido-methyl) ethanoate is described as providing a safe, non-toxic anti-inflammatory treatment for osteoarthritis. The patent filing claims that administration may reduce levels of serum amyloid A by about 40 to 60 percent, reduce levels of pro-inflammatory prostanoids by about 50 percent or more, and reduce levels of tumor necrosis factor alpha by about 40 to 60 percent. It is critical to note that patent applications are not peer-reviewed clinical evidence; these claims are assertions made in an intellectual-property filing and have not been validated in published randomised controlled trials in humans.
Evidence strength: For CEE/AlphaGEE specifically in joint/OA indications, the current evidence is preliminary and limited to in-vitro models. No peer-reviewed human clinical trials specifically examining CEE as a therapeutic agent for osteoarthritis were identified in the literature. The broader parent compound (creatine monohydrate) has been studied in an OA population: Cornish and Peeler in 2018 examined the effects of a 12-week creatine (n = 9) versus placebo (n = 9) supplementation protocol on inflammatory biomarkers in individuals diagnosed with knee osteoarthritis. Knee osteoarthritis is characterised by a low level of inflammation that may be responsible for the progressive destruction of the joint. The authors hypothesised that creatine supplementation (20 g·d⁻¹ for 1 week and then 5 g·d⁻¹ for 11 weeks) would lower systemic biomarkers of inflammation in the knee osteoarthritis participants when compared to placebo.
In-vitro evidence: The Leland et al. (2011) macrophage study (published in International Immunopharmacology) represents the only published investigation of CEE's effects on innate immune receptor expression. Researchers compared the ability of creatine monohydrate (CR), creatine ethyl ester (CEE), and creatinine (CRN) to suppress transcription of genes encoding toll-like receptor 2 (TLR-2), TLR-3, TLR-4, and TLR-7. Results were confirmed using immunohistochemistry. These particular receptors are triggered by a wide array of pathogens including gram-positive (TLR-2) and gram-negative (TLR-4) bacteria, and viruses (TLR-3, TLR-7). Overall, the data support the hypothesis that CR and CRN possess anti-inflammatory properties that impact the sensing arm of the innate immune system.
Importantly, CEE appears to possess immunostimulatory properties and increases expression of TLR-2, TLR-3, TLR-4, and TLR-7 in RAW cells, the opposite direction to the parent compound. This in-vitro finding raises questions about potential differential effects of CEE versus creatine on immune function, but it cannot be extrapolated to whole-organism or human outcomes without further research. The CDEK database lists CEE as having been evaluated in a Phase 4 clinical trial relevant to Multiple Sclerosis, alongside Arthritis, in trials involving two organisations. No published results from these trials were identified in the peer-reviewed literature at the time of writing.
Evidence strength: In-vitro only. No human clinical evidence.
A separate but related line of work concerns topical use of the N-acetylated derivative of creatine ethyl ester (N-acetyl-creatine ethyl ester, abbreviated "C15"). Research indicates that non-toxic creatine derivatives, especially N-acetyl-creatine ethyl ester, may be therapeutically effective on topical application or by superficial subcutaneous injection over sites of pain to rapidly alleviate or eliminate pain associated with various inflammatory conditions including arthritis, acute common headache, osteoarthritis, psoriatic arthritis, rheumatoid arthritis and various other pains associated with inflammation. Effective formulations included 1.5% to 9% concentrations of C15 for topical use. Clinical cases report pain relief within 2 minutes of application. The research highlights 17 case reports involving 12 subjects with diverse pain conditions.
Evidence strength: These findings come exclusively from case reports and are not confirmed by randomised controlled trials. Evidence is anecdotal/preliminary; no regulatory approval has been granted for these applications.
Dosages for creatine ethyl ester and the broader AlphaGEE designation reported in source literature are as follows:
No authoritative regulatory body (e.g., NIH ODS, EFSA, or WHO) has published an official recommended intake or tolerable upper limit specifically for creatine ethyl ester. Dosage claims in commercial literature are not sourced to peer-reviewed clinical trials.
The most consistently documented and clinically important safety signal unique to CEE — distinguishing it from creatine monohydrate — is its propensity to markedly elevate serum creatinine. CEE, but not creatine monohydrate, is converted into creatinine in the gastrointestinal tract. As a result, the use of CEE may be associated with elevated plasma creatinine levels. Since plasma creatinine is a widely used marker for renal function, the use of CEE may lead to a false assumption of renal failure.
This has been documented in published case reports. One case report describes how the consumption of creatine ethyl ester resulted in raised serum creatinine in the absence of true underlying kidney pathology. The abnormalities reversed after discontinuation of the supplement. A case of pseudo-renal failure was recognised and kidney function was concluded to be normal. The report addresses the mechanisms by which the ingestion of creatine ethyl ester can mimic the blood results expected in advanced renal failure, and confronts the problems faced when relying on serum creatinine as a diagnostic tool.
Supplemental creatine-induced creatinine elevations have the potential to be a red herring in the evaluation and management of a patient, as the serum creatinine values of those using creatine monohydrate or creatine ethyl ester in one study resulted in elevation consistent with Stage 2 and Stage 3 acute kidney injury (AKI) per the RIFLE criteria, respectively. The crucial clinical distinction is that elevated serum creatinine here reflects overproduction (due to CEE degradation), not reduced glomerular filtration. One case report showed creatinine was markedly elevated in a patient supplementing with creatine ethyl ester, but who had otherwise normal markers of renal function and whose serum creatinine normalised within a week.
The safety profile of alternative commercialised forms of creatine other than creatine monohydrate cannot be fully established because these novel formulations have been much less studied. In fact, creatine ethyl ester is a more unstable molecule, favouring increases in serum creatinine. There is very limited evidence that creatine supplementation is safe for those with pre-existing kidney diseases, a very important limitation in the literature. In addition, considering that a significant part of creatine consumers is composed of amateur and elite athletes who use many other (licit and/or illicit) substances, the impact of "polypharmacy" also involving creatine supplements as a burden to kidney function cannot be disregarded.
The degradation of CEE to biologically inert creatinine means that consumers are effectively converting a substantial fraction of ingested CEE into a waste product rather than into biologically active creatine. Creatine ethyl ester was developed with the aim of improving absorption over creatine monohydrate, though clinical evidence suggests its efficacy is not superior and may even be less effective due to rapid conversion to creatinine in the stomach. The ISSN 2017 position stand concluded that claims that different forms of creatine are degraded to a lesser degree than creatine monohydrate in vivo, or result in a greater uptake to muscle, are currently unfounded.
The in-vitro finding that CEE appears to possess immunostimulatory properties and increases expression of TLR-2, TLR-3, TLR-4, and TLR-7 in RAW cells is mechanistically distinct from the immunosuppressive profile of creatine monohydrate and creatinine. The implications of this finding for susceptibility to infection or autoimmune conditions in humans have not been characterised, and this finding should not be extrapolated to clinical recommendations without controlled human data.
Clinicians should be aware that patients consuming CEE may present with markedly elevated serum creatinine on routine blood chemistry panels that is not indicative of renal impairment. This distinction is important in differential diagnosis. The ingestion of creatine ethyl ester has been associated with elevated serum creatinine levels; its creatinine metabolite has a very short half-life, consistent with the rapid normalisation of serum creatinine after discontinuing the supplement. Measurement of glomerular filtration rate (GFR) using cystatin C or inulin clearance, rather than serum creatinine alone, provides a more reliable assessment of renal function in individuals supplementing with CEE.
Health conditions that Ethyl-alpha-guanido-methyl-ethanoate may help support.
Body systems that Ethyl-alpha-guanido-methyl-ethanoate may help support.
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