Receptor Theory

Paul Ehrlich proposed:

Drugs require direct interaction with tissue

A drug will not work unless it is bound

Drugs don’t have any supernatural properties by
which their mere presence causes an effect

Specificity defined by:

High structural conservation

ligand specificity

site specificity

Drug targets

Membrane receptors

Ion channels

carriers/transport molecules

enzymes

Drug-receptor binding

Occupation

governed by affinity

Activation

governed by efficacy

Drug Receptor interaction

equilibrium dissociation constant

linear

logarithmic

Quantitative aspects

Potency

effective dose

effective concentration

Antagonism

allosteric

pharmacokinetic

signaling blockade

physiological

chemical

Combinations

additive

synergistic/potentiating

Desensitization

tolerance

altered conformation of receptors

translocation of receptors

exhaustion of mediators

altered drug metabolism

physiological adaptation

Safety

Therapeutic Index

Certain safety factor