Tolerance Essay

Every day more than 90% of the world’s population consume caffeine, with global consumption estimated to be 120,000 tonnes per annum (Burchfield, 1997) and with the world’s population drinking such large amounts, tolerance can develop. Tolerance is when an organism no longer responds to the drug and as a result a higher dosage is required to produce the same effects (National Institute of Drug Abuse, 2007). A more precise definition of tolerance according to Baker and Tiffany, as cited in Fernandez, Kluwe, & Cooper (1977) and Kalant, LeBlanc, & Gibbins (1971) is that tolerance represents a shift in the dose response curve to the right. There are two competing theories, physiological and psychological, that try to explain how tolerance develops. Tolerance in regards to the physiological theory is divided into pharmacokinetic and pharmacodynamic tolerance. Pharmacokinetic tolerance occurs when there is a decrease in the amount of the substance reaching the target area, while pharmocodynamic tolerance occurs because there is a decreased response to the drug by cellular mechanism (Open Education Resources, n,d.)

Research has found that ethanol acts by binding and altering functions of membrane- bound ligand gated ion channels and voltage dependent ion channels (Chandler, Harris & Crews, 1998; Harris, 1998; Littleton & Little, 1994; Tabakoff & Hoffman, 1996).The way in which drugs such as ethanol cause tolerance is that once they exert their actions on specific receptor sites, they continue to occupy these receptor sites for a subsequent amount of time, thereby decreasing the amount of receptor sites that can stimulated by the same drug at a later date (Siegel, 1975, as cited in Scmidt & Livingstone, 1933) thus it takes more and more...

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...s it was expected that after drinking caffeine, consumers who regularly consumed high levels of caffeine would report smaller changes in energy levels than those who consumed caffeine on an irregular basis. Under the physiological theory it was also hypothesised that tolerance is a function of repeated administration of the drug of the substance. As the substance caffeine is not present in the decaffeinated condition, it is predicted that the changes in energy levels of the decaffeinated condition will not differ from those in the rooibos condition. A third hypothesis was formulated regarding the psychological theory states that tolerance is a conditioned compensatory response. Since caffeine causes an increase in energy levels, the decaffeinated group were expected to have lower energy levels than the rooibos group due to other influences other than bodily changes.