Caffeine enhancement

Theophylline and caffeine enhance renin release from the kidneys. 

Given the mixed results in the literature, it is difficult to know just how caffeine does affect memory. To some extent, the differential effects may depend on the memory assessment method (recall or recognition) and the time frame (immediate or delayed). Gender differences may also cloud the picture, as discussed above. Even when these differences are taken into account, however, unexplained discrepancies remain. One partial explanation may be that the differential effects of caffeine are a function of the subject s memory load. For example, Anderson65 found that caffeine enhanced low load memory tasks but was detrimental in high load tasks. This could be due to the increased arousal induced by the high load task, which, in the presence of caffeine, could produce overarousal. The drop in arousal output as the subject crossed the peak of the inverted U-shaped function could cause the memory deficits observed in some studies. 

Miller, L. and Miller, S., Caffeine enhances initial but not extended learning of a proprioceptive-based discrimination taskin non smoking moderate users. Percept Mot Skills 82(3), 891-898, 1996. 

James JE (1994). Does caffeine enhance or merely restore degraded psychomotor performance Neuropsychobiology, 30, 124-125. 

Several indirect neurochemical effects of methyixanthines contribute to their effects. Micromolar concentrations of caffeine enhance release of acetylcholine (Pedata et al. 1984). However, this effect is biphasic, augmenting release at 50 pM, but decreasing it at 0.5 pM. This effect is also modulatory, affecting stimulated, but not basal, release. Caffeine enhances acetylcholine release in the hippocampus, which is due to adenosine Al receptor subtypes (Carter et al. 1995). Conversely, chronic caffeine reduces the excitatory effect of acetylcholine in the cerebral cortex (Lin and Phillis... 

Caffeine increases the capacity of skeletal muscle. This effect is probably due to the release of intracellular Ca2+, and is observable in human performance. The contribution of central effects is also likely. Whether caffeine actually benefits exercise is contested (Spriet 1995 Dodd et al. 1993). Research does not consistently support caffeine enhancement of performance during high-intensity, short-term exercise. There is some evidence to suggest benefit during prolonged, moderate-intensity exercise. 

Carter AJ, O Connor WT, Carter MJ, Ungerstedt U. (1995). Caffeine enhances acetylcholine release in the hippocampus in vivo by a selective interaction with adenosine A1 receptors. J Pharmacol Exp Ther. 273(2) 637-42. 

Lu YP, Lou YR, Liao J, Xie JG, Peng QY, Yang CS, Conney AH. 2005. Administration of green tea or caffeine enhances the disappearance of UVB-induced patches of mutant p53 positive epidermal cells in SKH-1 mice. Carcinogenesis 26 1465-1472. 

Tablets, 1 mg, may be crushed before swallowing with water. Initially 1-2 tablets should be taken and thereafter, not more than 4 tablets should be taken in 24 h, the sequence should not be repeated for 4 days, and not more than 8 tablets should be taken in a week. Suppositories, 2 mg, are now preferred as part of stepped therapy (above) they are subject to the same maximum dose restrictions. Caffeine enhances both the speed of absorption and peak concentration of ergotamine and is often combined with it (though it may prevent sleep).

Zhang WY, Po AL. Do codeine and caffeine enhance the analgesic effect of aspirin A systematic overview. J Clin Pharm Ther 1997 22(2) 79-97. 

Kang W, Weiss M. Caffeine enhances the myocardial uptake of idarubicin but reverses its negative inotropic effect. Naunyn-Schmiedelbergs Arch Pharmacol 2003 367 151-155. 

Caffeine enhances the contractility of skeletal and cardiac muscle, and helps metabolize fat, thereby sparing muscle glycogen stores. It is also a central nervous system stimulant, which can aid in activities that require concentration. Many small studies using randomized, double-blind design have associated caffeine use with increased endurance times in athletes. - ... 

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