1979年8月20日 · Specifically, pA2 is the negative logarithm of the molar concentration of the antagonist which produces an agonist dose ratio of 2. This definition, when interpreted within the framework of Gaddum's formulation of competitive theory (2), relates pA2 to the dissociation constant of the antagonist as we shall show below.

2017年4月24日 · In the field of biochemistry, a pA2 value determines the important relationship between two drugs "competing" for effect on the same receptor. The "agonist" drug tries to affect the receptor. The "antagonist" drug attempts to block the agonist from working.

The pA2 value is the negative logarithm of the molar concentration of antagonist which causes a twofold shift of the concentration-response curve for agonist. The larger the pA2 the more potent the antagonist. where pAx is the negative log of the concentration of antagonist used and x is the concentration-ratio.

2024年3月19日 · The pA2 value represents the affinity of a competitive antagonist for a receptor as measured by its ability to shift an agonist's dose-response curve. The pD2 value represents a drug's potency as measured by its EC50. Both values are negative logarithmic transformations used for standardization and comparison.

2022年11月16日 · The effects of most drugs depend on the dose that is provided to the subject. In line with this, we have a concept called “dose descriptors”, which takes into account the relationship between a particular dose of a drug and the corresponding effect...

The pA2 is a measure of the affinity of a competitive antagonist for its receptor. The determination of the pA2 is made from experiments in which a fixed concentration of the antagonist is used along with graded concentrations of an agonist acting on the same receptor.

Various applications of p A x measurements are discussed based on the hypothesis that drugs and drug antagonists compete for receptors according to the mass law. Examples are given illustrating the use of p A x measurements to identify agonists which act on the same receptors and to compare the receptors of different tissues.

2023年5月9日 · PA2 and pD2 values are pharmacology concepts used to quantify drug interactions. The pA2 value represents the affinity of a competitive antagonist for a receptor as measured by its ability to shift an agonist's dose-response curve. The pD2 value represents a drug's potency as measured by its EC50.

2024年5月9日 · A high pA2 value means that the antagonist is highly potent in inhibiting the effects of the agonist. It suggests that the antagonist is capable of inhibiting the actions of the agonist at lower concentrations, making it an effective blocker of the agonist’s effects.

1981年1月1日 · The analgesic effect of a subcutaneous injection of morphine was assessed by the tail-flick method as an increase in the reaction time of the animal (tail flick) to avoid a painful stimulus. A reaction time of 1.61 0.02 seconds (mean SE) was recorded in the vehicle- …