General Principles Of Pharmacology/Drug therapy
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Most drugs interact with specific receptors. As will be discussed in the following section, this receptor site may be the same as the site for a neurotransmitter or hormone but may also be a site on an ion channel, enzyme, or other cellular constituent. The effective use of a new drug requires knowledge of its pharmacokinetics and sites of action. In particular, knowledge of the sites of action of a drug (i.e., the type of receptor) can help one to predict possible adverse drug interactions.
In order to define a specific receptor, three criteria should be satisfied: saturability, specificity, and reversibility:
Saturability: A finite number of receptors per cell (or per weight of tissue or protein) should be present as revealed by a saturable binding curve. By adding increasing amounts of drug, the number of drug molecules bound should form a plateau at the number of binding sites present.
Specificity: The drug should be structurally complementary to the receptor. This can be demonstrated by using a series of drugs varying slightly in chemical structure and showing that affinity differs with differing chemical structure. Also, if the drug is optically active, then the two isomers may have markedly different affinities.
Reversibility: The drug should bind to the receptor and then dissociate in its nonmetabolized form. This property distinguishes receptor-drug interactions from enzyme-substrate interactions.
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Previous Page: Types of Receptors
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