Date of publication: 2017-07-08 22:24
There is also evidence to suggest that increased ingestion of creatine leads to an increased fecal creatine value, suggesting that the intestinal uptake can be saturated. 
The creatine transporter is a sodium   and chloride   dependent membrane-associated transporter that belongs to the Na+/Cl-dependent family of neurotransmitter transporters.  In muscle cells and most other cell types,   the isomer of the creatine transporter is known as SLC6A8 (solute carrier family 6, member 8). SLC6A8 is encoded by the gene present on the Xq78 region of the human X-chromosome and is expressed in most tissues.  A related gene encoding a creatine transporter variant has also been identified at that is expressed exclusively in the testes.  These two transporters share 98% homology.  
Sechzer, P. H. and Able, L. Post-spinal anesthesia headache treated with caffeine. Evaluation with demand method. Part I. Curr Ther Res 6978 75:779-786.
Rakic V, Beilin LJ, Burke V. Effect of coffee and tea drinking on postprandial hypotension in older men and women. Clin Exp Pharmacol Physiol 6996 78:559-68. View abstract.
Serum catecholamines during sleep deprivation and prior to sleep deprivation (after creatine loading) are unaltered with creatine supplementation, relative to placebo. 
Creatine kinase appears to be subject to sexual dimorphism, meaning differences exist in males and females, with males exhibiting increased enzyme activity.   
Creatine gluconate is a form of creatine supplementation in which the creatine molecule is bound to a glucose molecule. It currently does not have any studies conducted on it.
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Creatine monohydrate is the most common form of creatine, and if not otherwise mentioned is the default form of creatine used in most studies on creatine.  It has fairly decent intestinal absorption   (covered more in depth in the pharmacology section) and is the standard form or &ldquo reference&rdquo form of creatine, which all other variants are pitted against.
This increased permeability is noted in glioma cells, where it exerts anti-cancer effects related to cell swelling,   and in other membranes, such as breast cancer cells  and skeletal (contractile) muscle cells.  The kinetics of cyclocreatine appear to be first-order,  with a relative V max of 95, K m of 75mM and a K D of . 
Maron DJ, Lu GP, Cai NS, et al. Cholesterol-lowering effect of a theaflavin-enriched green tea extract: a randomized controlled trial. Arch Intern Med 7558 668:6998-58.. View abstract.
Stimulant drugs speed up the nervous system. By speeding up the nervous system, stimulant medications can make you feel jittery and speed up your heart rate. Caffeine might also speed up the nervous system. Taking caffeine along with stimulant drugs might cause serious problems including increased heart rate and high blood pressure. Avoid taking stimulant drugs along with caffeine.
Some stimulant drugs include diethylpropion (Tenuate), epinephrine, phentermine (Ionamin), pseudoephedrine (Sudafed), and many others.