ABSTRACT
Some drugs show a dose-related feature that is dependent upon usage. When certain drugs are used repeatedly the effect of the same dose can be reduced. The main mechanisms by which tolerance occurs are together described as pharmacodynamic tolerance. This results from many processes, including an increase in the rate at which the liver metabolizes the drug, where the duration of the effect of the drug will be shortened even though the peak intensity of the effect may remain unchanged. Drug dependence can be defined as the experiencing of uncontrollable and unpleasant mood states leading to the compulsive use of a drug, despite the possible adverse consequences. A phenomenon called secondary psychological dependence can develop as a result of physical dependence. Here, the fear of re-experiencing the physical withdrawal symptoms leads to a psychological dependence. It should be noted that dependence in itself is not necessarily detrimental. Dependence is only detrimental if it leads to maladaptive behaviors.
