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Affinity describes how well a drug can bind to a receptor. Faster or stronger binding is represented by a higher affinity, or equivalently a lower dissociation constant. The EC 50 should not be confused with the affinity constant, K d. While the former reflects the drug concentration needed for a level of tissue response, the latter reflects ...
Intrinsic activity (IA) and efficacy (E max) refer to the relative ability of a drug-receptor complex to produce a maximum functional response. This must be distinguished from the affinity, which is a measure of the ability of the drug to bind to its molecular target, and the EC 50, which is a measure of the potency of the drug and which is proportional to both efficacy and affinity.
The ED50 is commonly used as a measure of the reasonable expectancy of a drug effect, but does not necessarily represent the dose that a clinician might use. This depends on the need for the effect, and also the toxicity. The toxicity and even the lethality of a drug can be quantified by the TD 50 and LD 50 respectively. Ideally, the effective ...
Recognizing drug candidates with potentially suboptimal TI at the earliest possible stage helps to initiate mitigation or potentially re-deploy resources. TI is the quantitative relationship between pharmacological efficacy and toxicological safety of a drug, without considering the nature of pharmacological or toxicological endpoints themselves.
For a response of 0.25a.u., Drug B is more potent, as it generates this response at a lower concentration. For a response of 0.75a.u., Drug A is more potent. a.u. refers to "arbitrary units". In pharmacology , potency or biological potency [ 1 ] is a measure of a drug's biological activity expressed in terms of the dose required to produce a ...
IC 50 / pIC 50 values represent binding affinity only and do not reflect efficacy or pharmacokinetics, and some compounds listed are GABA A antagonists rather than agonists (e.g. flumazenil). Low IC 50 or high pIC 50 values indicate tighter binding (pIC 50 of 8.0 = IC 50 of 10nM, pIC 50 of 9.0 = IC 50 of 1nM, etc.)
The parameters of the dose response curve reflect measures of potency (such as EC50, IC50, ED50, etc.) and measures of efficacy (such as tissue, cell or population response). A commonly used dose–response curve is the EC 50 curve, the half maximal effective concentration, where the EC 50 point is defined as the inflection point of the curve.
Compared to the second-generation NSAAs, enzalutamide and apalutamide, bicalutamide has inferior potency and efficacy but similar tolerability and safety and a lower propensity for drug interactions. Relative to steroidal antiandrogens like cyproterone acetate and spironolactone , bicalutamide has better selectivity in its action, superior ...