Phenothiazine drugs, including chlorpromazine and levomepromazine, have been being widely used as neuroleptics (major tranquilizers), antiparkinsonian drugs and antihistaminics for a long time . Table 1.1 shows chemical structures of representative phenothiazines. These drugs show blocking action on D2 receptors of dopaminergic neurons; there is close relationship between the receptor blocking and tranquilizing actions. The dopamine D2 receptor-blocking actions provoke extrapyramidal symptoms, such as muscular stiffness, tremor and ptyalism.
In one sense, pharmacology can be considered a “good
news, bad news” scenario. The good news is that
exciting and innovative changes in drug therapy continue
to occur at lightning speed. The bad news is that
it is often difficult for health care practitioners to stay
abreast of this rapidly changing field. Oftentimes,
drug therapies that were considered state-of-the-art
only a few years ago are now outdated and replaced by
more contemporary treatments.
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