Pharmacodynamic inhibition

The therapeutic efficacy of a dmg is generally measured in terms of ED q or ID q which represent the concentration of dmg which produces 50% of the maximum effect or 50% of maximum inhibition. LD q represents the concentration of dmg that produces 50% fataUties in test animals. The therapeutic index is the ratio of the ED q versus LD q. Detailed descriptions of the terminology and fundamental principles of pharmacology are available (32) (see Pharmacodynamics). 

Vigilance for drug-drug interactions is required because of the greater number of medications prescribed to elderly patients and enhanced sensitivity to adverse effects. Pharmacokinetic interactions include metabolic enzyme induction or inhibition and protein binding displacement interactions (e.g., divalproex and warfarin). Pharmacodynamic interactions include additive sedation and cognitive toxicity, which increases risk of falls and other impairments. 

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. 

Figure 3 Rodent pharmacodynamic effects versus CbjU for 6. Dashed lines represent a twofold separation from the in vitro functional assay EC50 (122 nM, dashed arrow). mSLA, mouse spontaneous locomotor activity mPPI, mouse prepulse inhibition DRC, dose-response curve SD, single dose. (See Color Plate 4.3 in the Color Plate Section.)...

Whether the pharmacodynamic advantages of dutasteride confer clinical advantages over finasteride is unknown. Dutasteride inhibits types I and II 5a-reductase, whereas finasteride inhibits only type II. Dutasteride more quickly and completely suppresses intraprostatic DHT (vs. 80% to 90% for finasteride) and decreases serum DHT by 90% (versus 70%). 

A paper detailing the properties of the multikinase inhibitor ABT-869 (7) did not indicate whether plasma protein binding data were used in the optimization leading to this highly protein-bound (mouse 98.2%, human 99.0%) compound [45]. A dose which provided a 69% reduction in tumor growth and >50% inhibition of receptor phosphorylation and pharmacodynamic response afforded plasma concentration that remained above the cellular IC50 for receptor phosphorylation in the presence of plasma for 4 of 12 h in the bid dosing cycle. 

Traditionally, the duration of a toxicity study depends on the intended clinical use and disease duration. The potential immunogenicity of the human protein is a significant issue since antibody binding can partially or completely inhibit the biological activity of that protein, affect its catabolism or alter its distribution and clearance. Any multiple-dose study therefore should include evaluation of the impact of antibody formation, including their neutralizing capacity. However, antibody formation in itself should not be a reason for termination of a toxicity study, particularly if the antibodies are not neutralizing or do not alter the pharmacodynamics of the protein. 

Pharmacokinetic/pharmacodynamic evaluated using indirect response modeling with inhibition of input... 

The terms proof of principle and proof of concept are used more or less synonymously and pertain to the criteria that must be fulfilled in human studies before an NME can be considered to be a candidate for FD. These are particularly useful terms when applied to a drug thought to act by a novel mechanism of action. Eor example, a drug may be the first known inhibitor of a particular enzyme or receptor and the proof of principle will be a demonstration that such inhibition results in a desired pharmacodynamic or clinical endpoint. The terms are perhaps less... 

Plumb, J.A., Finn, P.W., Williams, R.J., Bandara, M.J., Romero, M.R., Watkins, C.J. et al. (2003) Pharmacodynamic response and inhibition of growth of human tumor xenografts by the novel histone deacetylase inhibitor PXDIOI. Molecular Cancer Therapeutics, 2, 721-728. 

The group at Millennium Pharmaceuticals has claimed MLN-8054 (97) to be the first kinase inhibitor selective for Aurora-A over Aurora-B, which gives robust inhibition of human tumor xenografts [228-230]. Treatment of cultured human tumor cells with 97 resulted in the accumulation of mitotic cells with spindle abnormalities, a phenotype consistent with selective Aurora-A inhibition. In a pharmacodynamic model the time-dependent accumulation of... 

A number of limitations related to PK/PD modeling are also a reality in situations where predictability of the animal model to man is questionable, where the time course of the pharmacodynamic effect cannot be assessed for drug candidates and when, for example, no accessible/ valid pharmacodynamic endpoint for PK/PD is available. The relevance of the animal model for human could be addressed to some extent at least by measuring relative potency in animal versus man in vitro. In situations where no relevant PD endpoint is available (e.g., for CNS efficacy models), effects at target level (i.e., enzyme inhibition, receptor occupancy) might represent a valuable alternative. In this context however the level and duration of target effect required for clinical efficacy requires careful considerations. 

Absorption, distribution, metabolism, and elimination P-glycoprotein Pharmacokinetics/pharmacodynamics Concentration for 50% inhibition of the function of the delayed rectifier channel encoded by the human ether... 

Fig. 14. Schematic description of pharmacokinetic and pharmacodynamic determinants of drug action. Distribution from the measurement site (Cp) to the biophase (Ce), determined by a distribution rate constant is followed by drug-induced inhibition or stimulation of the production (k ) or removal (A out) of a mediator (R), transduction of the response R and further transformation of R to the measured effect E, if the measured effect variable is not R. (Modified from Jusko WJ, Ko HC, Ebling WF. Convergence of direct and indirect pharmacodynamic response models. J Pharmacokinet Biopharm 1995 23 5-6.)...

NSAID treatment alone. They may be used concurrently with NS AIDS. It mostly takes 1-3 month for their anti-inflammatory action to become apparent. The pharmacodynamics of these antimalarials in RA is uncertain. Possible mechanisms include decreased leukocyte chemotaxis, stabilization of lysosomal membranes, inhibition of DNA and RNA synthesis and trapping of free radicals. 

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