That being said, I'd make the case that the references attached to the half-lives that you're talking about give the conditions under which those half-lives were obtained. DMacks 06:02, 24 July 2007 (UTC) Yes, the rate equation is dependent on the amount of the reactant present. For caffeine, we're talking about biological half-life. The time necessary to metabolize one half a mass of caffiene is going to be highly dependant on how much caffiene is actually present, and any time listed should be qualified with a range of mass it applies to.- Joshbw 04:56, 24 July 2007 (UTC) Radioactive half-life is just one specific example of exponential decay, a fairly common mathematical relationship seen in many branches of science. Further, In terms of it being metabolized by the body, this is a chemical reaction and relies very heavily on the concentrations and volumes of the various chemicals involved in the reaction. Caffiene does not have a half life in this sense, as it is not radioactive, so I believe the use of half-life to be incorrect. First, half life is a specific scientific term to discus the period necessary for half of a mass of substance to suffer radioactive decay. I believe the use of half life to be incorrect here. The reduction in adenosine activity results in increased activity of the neurotransmitter dopamine, largely accounting for the stimulatory effects of caffeine." dil 13:47, 7 March 2007 (UTC) Therefore, caffeine acts as a competitive inhibitor. The caffeine molecule is structurally similar to adenosine, and binds to adenosine receptors on the surface of cells without activating them (an "antagonist" mechanism of action). To quote the article as it stands now: "Once in the brain, the principal mode of action of caffeine is as an antagonist of adenosine receptors found in the brain. dil 20:55, 15 December 2006 (UTC) In the book, The World Of Caffeine by Weinberg and Bealer, they say that "scientists are still unsure as to what degree and what respects caffeine's metabolites are responsible for its effects, although most would agree that its methylxanthine products contribute to the physical and mental stimulation which are the hallmark of caffeine consumption." Teloscientist 03:54, 7 March 2007 (UTC) Interesting - I'd like to see a reference on that one. Therefore the stimulant effects would be lessened as conversion to the metabolites and the eventual rate of clearance is increased. The activity of CYP1A2 (the cytochrome P450 enzyme that metabolizes caffeine via dealkylation at the nitrogens as shown in the article) is enhanced by nicotine. In terms of metabolism, I believe the stimulant effects of caffeine are a result of caffeine itself, not the result of one of its metabolites. all at once methods of drinking coffee to maximize caffeine performance. at one point i was told that cigarettes increase the amount of caffeine the body is able to metabolism - is the case just that smoking makes the body process it faster and thus get a bigger (but faster) rush? JoeSmack Talk 17:54, 15 December 2006 (UTC) Not sure on the slow and steady vs. I also see down there that smoking increases the metabolism, shortening the half life of caffeine. if a coffee drinker drinks coffee more slowly, are they getting more caffeine from it or giving a longer plateau of caffeinated time? the body can obviously only absorb so much caffeine at one time, like say, nicotine. i have a question or two regarding caffeine and metabolism. If not removed, it should be reworded for clarity. Otherwise, the "3 times a day" should be removed. ![]() And in fact, the research indicates that the groups this research was done on received the entire dosage in one go. Is this talking about a person who takes 400mg of caffeine each time they take it, and they take it three times per day, for a total of 1200mg in a day? No, the actual article only mentions 400mg and 300 mg, respectively, used in one day. I am not sure who wrote this, but the original research that this is based on does not mention anything about "3 times a day," and as such, the entire "3 times a day" part is very confusing. ![]() Complete tolerance to subjective effects of caffeine was observed to develop after consuming 300 mg 3 times per day for 18 days, and possibly even earlier." In this section, the following is listed: "Complete tolerance to sleep disruption effects of caffeine develops after consuming 400 mg of caffeine 3 times a day for 7 days.
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