Drug Characteristics

The impact of hemodialysis on drug therapy depends on drug characteristics (e.g., molecular weight, protein binding, and Vp), dialysis prescription (e.g., dialysis membrane composition, filter surface area, blood and dialysate flow rates, and reuse of the dialysis filter), and clinical indication for dialysis. 

The in vivo absorption process is the outcome of a complex series of events and depends on a multitude of parameters related to drug characteristics as well as to physiological aspects of the gastrointestinal (GI) tract [93], A summary of the most important factors influencing the rate and extent of intestinal absorption is given in Table 8.1. 

Clinical Trial Application (CTA) has to be submitted to Health Canada seeking permission to conduct clinical trials. The submission should include information regarding drug characteristics, test data, animal studies, and clinical protocol. A clinical trial may be stopped when either it is shown to be unsafe or dramatic benefits are obtained. The approval process may be fast-tracked if a drug is shown to have substantial benefits, such as for treatment of life-threatening or severely debilitating conditions. 

Another drug characteristic that can be compared by use of ED50 values is potency. Figure 2.4 illustrates the mean dose-response curves of three hypothetical drugs that increase heart rate. Drugs a and b produce the same maximum response (an increase in heart rate of... 

The drug expiration date for a single batch exhibits a 95% confidence that the average drug characteristic of the dosage units in the batch is within specifications up to the end of the expiration date. The 95% one-sided lower confidence bounds for the mean degradation line is shown in Figure 1. 

The purpose of building a virtual human population is to capture all the complex interplay between different sources of variability mentioned above in the form of a network of system information that interacts with drug characteristics measured using in vitro studies and indicates potential co-variations determining the drug therapy outcome (for an example, see Fig. 16.4). 

Determination of clearance rate (for first-order reactions) also allows us to calculate another very important drug characteristic, namely its half-life (t112), according to the following formula ... 

Clonazepam 0.5 mg t.i.d. 2 mg t.i.d. 1% 100% 100% 100% Although no dose reduction is recommended, the drug has not been studied in patients with renal impairment recommendations based on known drug characteristics not clinical trials data NC NC NC... 

---