Potency of a drug refers to -
Ans. is 'c' i.e., Dose that tequires to produce response o Generally, the intesity of response increases with increase in dose and dose-response curve is a rectangular hyperbola. This is bacause drug-receptor interaction obeys law of mass action. If, however the dose is plotted on a log arithmic scale (log dose-response curve), the becomes sigmoid and a linear relationship between log of dose and the response is seen only in intermediate zone (30-70% response).o Dose response curve can determine three important parameters :A. Efficacy# It refers to maximal response (effect) that can be elicited by the drug.# The upper limit of the DRC (dose response curve) is the index of drug efficacy.# Efficacy is more decisive factor than potency in the choice of the drug.# In case of'non-competitive' inhibitor, there will be flattening of DRC, i.e. efficacy will decrease without a change in potency.B. Potency# It refers to the amount of drug needed to produce a certain response.# The position of DRC on the dose axis (X-axis) is the index ofpotency.# A DRC positioned rightward indicates lower potency, i.e. more dose is required to produce the effect.# Drug producing same response at lower dose are more potent and are on left side of DRC.# In case of'competitive9 inhibitor curve will shift to right Le. potency will decrease without a change in efficacy \C. Slope# If the DRC is steeper, that means the response will increase dramatically with slight increase in dose.# Thus, drugs with steeper DRC have harrow therapeutic index.
Affinity of drug to bind to receptor
Affinity of drug that binds to receptors and activates it
Dose that requires to produce response
Maximum response a drug can produce
Pharmacodynamics