MODA

The EC50 is the concentratin of the agonist that causes 50% of the maximum response 

The affinity is the tendency of the drug to bind to its receptor 

The efficacy is the tendency for the drug (once bound) to activate its receptor. 

• Toxic dose               or         LD 50%     (lethal dose)
• Therapeutic dose                  ED 50%     (experimental dose)

That the drug has a wide safety margin e.g penicillin 

An agonist is a substance/drug that binds to recpetors and produces a response. 

An antagonist binds to a receptor, therefore preventing the agonist from binding, but it does not cause a response.

AGONIST..... affinity AND efficacy

ANTAGONIST... affinity but NO efficacy 

It occupies the recpetors so that more agonist is needed to produce any given response. 

Causes the log concentration/response curve for the agonist to be shifted to the right.

• The potency of the agonist refers to the concentration casuing a particular magnitude of response. It is measured using the EC₅₀
• High EC₅₀ = less potent
• Low EC₅₀ = more potent 

A partial agonist is an agonist that fails to produce a maximum response even when it occupies 100% of the receptors.