Pharmacodynamics quantitative aspects

The effectiveness of drug targeting should be evaluated by taking into account not only pharmacokinetic aspects, but also the pharmacodynamic aspects. The latter include the concentration-effect relationship in the target tissue and at the sites where toxicity may occur [7,12]. The therapeutic effect of the drug and its toxic effect may be different with regard to their mechanisms, and hence their concentration-effect relationship may also be different, both qualitatively (different PD models) and quantitatively (different model parameters). 

It was noted in the previous section that both pharmacokinetics and pharmacodynamics are concerned with relationships over time. One illustration of the fundamental importance of the rates of these processes can be seen in the plasma concentration-time profile (also known as the plasma-concentration curve) for an administered drug. This was introduced in Section 4.2.1, along with several quantitative pharmacokinetic terms used to describe and quantify aspects of the plasma concentration-time profile ... 

This chapter lays down the conceptual framework for understanding the quantitative and temporal aspects of drug-drug interactions, hereafter called drug interactions for simplicity. Emphasis is placed primarily on the pharmacokinetic aspects, partly because pharmacokinetic interactions are the most common cause of undesirable and, to date, unpredictable interactions and also because most of this book is devoted almost exclusively to this aspect and indeed to one of its major components, drug metabolism. Some pharmacodynamic aspects are also covered, however, for there are many similarities between pharmacokinetic and pharmacodynamic interactions at the molecular level and because ultimately one has to place a pharmacokinetic interaction into a pharmacodynamic perspective to appreciate the likely therapeutic impact (1-5). 

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