Assays pharmacology

Alberts, D. S., Chen, H.-S. G., and Salmon, S. E., In vitro drug assay Pharmacologic considerations. Prog. Clin. Biol. 

There should be specific, saturable binding to the receptor, accompanied by pharmacological characteristics appropriate to the functional effects, demonstrable using a radioactive, eg, tritium or iodine-125, ligand to label the receptor. Radioligand binding assays (1,6) have become a significant means by which to identify and characterize receptors and enzymes (see Immunoassays Radioactive tracers). Isolation of the receptor or expression of the receptor in another cell, eg, an oocyte can be used to confirm the existence of a discrete entity. 

It was apparent that the FDA recognized the ability of the pharmaceutical industry to develop chiral assays. With the advent of chiral stationary phases (CSPs) in the early 1980s [8, 9], the tools required to resolve enantiomers were entrenched, thus enabling the researcher the ability to quantify, characterize, and identify stereoisomers. Given these tools, the researcher can assess the pharmacology or toxicology and pharmacokinetic properties of enantiopure drugs for potential interconversion, absorption, distribution, and excretion of the individual enantiomers. 

In general, there are advantages and disadvantages to both assay formats and both are widely employed in pharmacological research. The specific strengths and weaknesses inherent in both approaches are discussed in more detail in Chapters 4 and 5. As a preface to the consideration of these two major formats, a potential issue with both of them should be considered namely, dissimulations between the concentrations of drugs added to the experimentally accessible receptor compartment and the actual concentration producing the effect. 

Christopoulos, A. (2000). Quantification of allosteric interactions at G-protein coupled receptors using radioligand assays. In Current protocol in pharmacology, edited by Enna, S. J., pp. 1.22.21-1.22.40. Wiley and Sons, New York. 

Recombinant assays have revolutionized pharmacology and now functional systems can be constructed with engineered levels of responsiveness (i.e., through difference in receptor levels or co-transfection of other proteins). 

Schild analysis, like all pharmacological tools, necessarily is predicated on the idea that the drugs involved have one and only one pharmacological activity. This often may not be the case and selectivity is only a function of concentration. If the concentrations used in the assay are below those that have secondary effects, then the tool will furnish the parameter of interest with no obfuscation. However, if a secondary effects are operative in the concentration range required to measure antagonism then the resulting parameter may be tainted by this secondary activity. 

Before an antiviral agent becomes a drug, advanced toxicity testing, pharmacological combination, and drug-interaction studies are needed. The use of new cell-based assays that can predict mitochondrial toxicity, lactic acidosis, peripheral neuropathy, anemia, hypersensitivity, lipodystrophy, and other potential side effects can alleviate these issues (Stuyver et al. 2002). 

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