For a number of years now, creatine supplements have been used by athletes of all calibers participating in a variety of sports. So far, research has shown benefits when there is a demand of short duration but high intensity and high power/strength development. Due to the potential benefits of having increased creatine, but the difficulty in obtaining it from food, supplementation of creatine has become popular. Eastern European countries have reported experimentation as early as 1960, but the developments in non-food creatine supplementation really took hold in the early 1990s.3 At first, only low-dose creatine was available as a supplement and its effects had yet to be proven. In 1993,  Experimental and Applied Sciences (EAS) brought Phosphagen to the market and thus came the birth of commercially available creatine. 4

Our body keeps a reserve of creatine in the form of creatine phosphate stored in the muscles. It is an  important immediate source of energy in the body and is used when the body requires an immediate source of energy with activities lasting about 1 second such as a throwing a shot-put or making a vertical jump.1 The phosphate bound to the creatine is given up to convert adenosine diphospate (ADP) back to adenosine triphophosate (ATP). ATP is the main source of energy used by the cells to accomplish any form of work.1 Keeping the creatine stores high allows the body to continue to perform, especially when the demands are of short duration, high intensity, and require power. Because other animals also store creatine in their muscles, a person can increase the amount of creatine in their system by consuming food such as meat and fish. Unless consumption of these products exceeds 1 pound per day on a regular basis, a person would only be able to obtain about 3-4 grams of creatine. 2

Creatine supplements come in many forms including capsules, caplets, powders, and pre-made drinks. Creatine is easily absorbed by the body and has high bioavailability (meaning that very the body loses little creatine in the digestion process). Perskey, et. al. comment that “creatine is most probably actively absorbed from the gastrointestinal tract in a similar way to amino acids and peptides.” 5
 
Creatine monohydrate is the oldest of the products on the market, but is not the only one available. Other forms that have come to the market include (to name a few) liquid creatine, creatine citrate, creatine alpha-ketogluterate, and most recently creatine ethyl ester, or CEE. They work on the same principle as creatine monohydrate, but supposedly some are absorbed more quickly, or have more available creatine for the body to use. CEE has been around since about 2004 and is showing some promise as a superior creatine. It does appear to have the beneficial effects of creatine monohydrate without the typical bloating and upset stomach. More of CEE seems to enter into the system and so it can be loaded faster. Since more is absorbed, it may require less amount of intake to get the same effects.6  There seems to be some in-the-field evidence building about the benefits of CEE, but as with all the “other” (other than creatine monohydrate) creatine products, there is no conclusive evidence.

References
1.    Howley, Edward & B. Don Franks. Fitness Professional's Handbook. Human Kinetics 2007. pp 446
2.    Williams, Melvin H., Richard B. Kreider, J. David Branch. Creatine: The Power Supplement.  Human Kinetics, 1999.  pp 14
3.    Williams, Melvin H., Richard B. Kreider, J. David Branch. Creatine: The Power Supplement.  Human Kinetics, 1999.  pp 11
4.    http://en.wikipedia.org/wiki/Creatine_supplements. Found 1/22/09
5.    Persky AM, Brazeau GA, Hochhaus G.  “Pharmacokinetics of the dietary supplement creatine.” Clinical Pharmacokinet. 2003;42(6):557-74
6.    O’Bryne, James. Creatine monohydrate and creatine ester ethyl review. www.realsolutionsmag.com. Found 1/22/09