DOSE RESPONSE CURVES

Many drugs function by the receptor mechanism, for instance acetylcholine binding to its receptor. What we mean by receptor is some sort of binding site protein on the cell surface that binds drugs, and does something on a molecular level to make some sort of pharmacological response (ie. dilation of pupil, change of heartrate, etc.). What we’ll be discussing now are drugs operating via a receptor mechanism.

The pharmacological response is directly proportional to the number of receptors occupied by the drug. As you gradually increase the drug dose, more receptors are occupied. At first, the number of occupied receptors is linearly proportional to the dose. As you get to high drug doses, you eventually saturate the receptors and produce the maximum possible response. If you add more drug beyond that there’s no additional response because the receptors are saturated.

A little algebra (“its really very simple”):

D= drug

R= receptor

So you’ve got a reversible chemical reaction:

D + R  DR

Category: Pharmacology Notes