The higher the Kd value, the weaker the binding and the lower the affinity. The strength of the binding (interaction) of a ligand and its receptor can be described by affinity. The value of KB was calculated according to the following new power equation: KB = IC50/(l + A(K)/Kp) = IC50/, where IC50 is the concentration of the antagonist producing 50% inhibition, A is the concentration of the agonist against which the IC50 is being determined and KP is the apparent equilibriumĪffinity is inversely proportional to the potency of a drug, where Kd is the dissociation constant. KD (dissociation constant) is the inverse of the drug affinity to the binding site ( affinity = 1 / KD )Ĭonsequently, how do you calculate KB in pharmacology? KD is the concentration at which 50% of binding sites (receptors) are occupied by drug. One may also ask, what does KD mean in pharmacology? KD = dissociation CONSTANT. Kd measures how tightly a drug binds to its receptor. The meaning of pA2 is the affinity of the antagonist to the receptor (4). Kd: The pharmacologic response depends on the drug binding to its target as well as the concentration of the drug at the receptor site.
The value of pA2 is a negative logarithm of the molar concentration of competitive antagonist, which requires a doubling of the concentration of agonist to compensate for the action of the antagonist. At low temperature, the B Max value for the hydrophilic antagonist 3 HNMS was significantly lower than that of the more lipophilic antagonist 3 HQNB, whereas at 37C the values were. A study on mAChRs expressed in the neuroblastoma cell line SK-N-SH illustrates this point (Fisher, 1988). The pA2 value indicates the concentration of antagonist when double the agonist is required to have the same effect on the receptor as when no antagonist is present. The polarity of the ligand may affect B Max and K d. In the field of biochemistry, a pA2 value determines the important relationship between two drugs "competing" for effect on the same receptor.