How is the drug-receptor binding relationship?

When a drug or an endogenous ligand binds a receptor, this will result in a response (molecular level) When a sufficient number of receptors bind receptors on a cell, the cumulative effect will become apparent in the cell, and if all receptors are occupied, this is a maximal response (cellular level) When response occurs on many cells, it can be seen at the level of an organ or a patient.