Pharmacokinetics and Drug Receptors

The generation of mice with disrupted genes should allow the evaluation of the pharmacokinetic and pharmacodynamic consequences of the complete, specific inhibition of particular drug enzymes, transporters or receptors. 

For a drug to interact with a target, it has to be present in sufficient concentration in the fluid medium surrounding the cells with receptors. Pharmacokinetics (PK) is the study of the kinetics of absorption, distribution, metabolism, and excretion (ADME) of drugs. It analyzes the way the human body deals with a drug after it has been administered, and the transportation of the drug to the specihc site for drug-receptor interaction. For example, a person has a headache and takes an aspirin to abate the pain. How does the aspirin travel from our mouth to reach the site in the brain where the headache is and act to reduce the pain ... 

At the cellular level, the various types of receptor, transporter, enzyme and ion charmel are all chiral in form. Thus although the enantiomers of a drug may have identical physicochemical properties, the way in which they may interact with chiral targets at the level of the cell will give rise to different pharmacod)mamic and pharmacokinetic properties. A few simple examples will illustrate how taste and olfactory receptors can differentiate between enantiomers. Thus R-carvone tastes like spearmint whereas the S-isomer tastes like caraway. Similarly, R-limolene smells like lemon whereas the S-enantiomer tastes of orange. 

In the last chapter receptor-based diagnostic radiopharmaceuticals are reviewed including considerations on drug design, on receptors, and on receptor imaging with the objective of modifying the pharmacokinetics of these agents. 

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