Relative potency

Relative potency alone does not determine dmg selection because maximal effectiveness is similar for all agents. A single daily dose of any sulfonylurea, except tolbutamide, is sometimes adequate to control blood glucose in NIDDM patients. 

Compounds that have agonistic properties at glutamate or aspartate receptors are also CNS stimulants, readily cause convulsions, and presumably could also be employed as analeptics. Three separate excitatory amino acid receptor subtypes have been characterized pharmacologically, based on the relative potency of synthetic agonists. These three receptors are named for their respective prototypical agonists A/-methyl-D-aspartate [6384-92-5]... 

Species Tested. In addition to the variation in susceptibiUty to chemically induced toxicity among members within a given population, there may be marked differences between species with respect to the relative potency of a given material to produce toxic injury. These species differences may reflect variations in physiological and biochemical systems, differences in distribution and metaboHsm, and differences in uptake and excretory capacity. 

This review briefly summarises the available evidence on the relative potency of the phytoestrogens, and discusses the evidence that beneficial effects on human diseases may potentially arise from consumption of foodstuffs containing these compounds, with particular regard to those effects that have been suggested as possibly being related to the hormone-receptor mediated activities of the phytoestrogens. Certain causes for concern regarding these compounds are also addressed. 

FIGURE 10.3 Comparative potencies of two agonists in two receptor systems containing the same receptor at different receptor densities, (a) Relative potency in system with high receptor density (x, = 500, x2= 100). The potency ratio = 5. (b) Dose-response curves for same two agonists in receptor system with 1/100 the receptor density. Potency ratio = 1.3. 

Null method, physiological or pharmacological effects are translations of biochemical events by the cell. The null method assumes that equal responses emanate from equal initial stimulation of the receptor therefore, when comparing equal responses, the complex translation is cancelled and statements about the receptor activity of agonists can be made. Relative potencies of agonists producing equal responses thus are interpreted to be measures of the relative receptor stimuli produced by the agonists at the receptor see Chapter 5.6.2. 

Relative potency, absolute agonist potency is the product of receptor stimulus (brought about by agonist affinity and efficacy) and the processing of the stimulus by the cell into an observable response. Because this latter process is system (cell type) dependent, absolute potencies are system-dependent measures of agonist activity. However, when... 

The affinity of a drug is the ability of that drug to bind to the receptor. The efficacy of an agonist is its ability to activate (or inactivate in the case of an inverse agonist) the receptor. The relative potency of an agonist (with respect to another agonist at the same receptor) is therefore determined by both its affinity and efficacy and only gives an indication of the relative concentrations at which they produce a particular response. 

Thorpe, K.L., Cummings, R.I., and Hutchinson, T. et al. (2003). Relative potencies and combination effects of steroidal estrogens in fish. Environmental Science and Technology 37, 1142-1149. 

Fig. 25.5 Graphical representation of a two-by-two assay response. X is the horizontal distance between the two lines. The antilog ofX gives the relative potency of the standard and test.

With tso as an index of carcinogenicity, an interspecies relative potency (IRP) can be defined, e.g.,... 

Table 2 is a summary of drug discrimination testing data for drugs that completely substitute in rats trained to discriminate saline from (-t-)-MBDB-HCl (1.75 mg/kg 7.19 pmol/kg). These data are arranged in order of decreasing relative potency. 

Table 2 summarizes results of neurotoxicity studies that have utilized the same regimen of drug injections (twice daily for 4 days) and survival times (2 weeks). In addition, the ability of these drugs to suppress milk intake in rats is also presented. It is clear that ring-substituted amphetamines are more potent in terms of absolute dose required to reduce amine content than is the parent compound amphetamine. With regard to relative potency, METH is toxic to DA and 5-HT neurons at doses that are more than tenfold higher than doses that produce anorexia, whereas fenfluramine,... 

TABLE 6. Relative potencies of amphetamine derivatives at selected brain... 

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