Key definitions

• Pharmacology: the study of the manner in which the function of living tissues and organs is modified by chemical substances
• Pharmacology: what a drug does to the body
• Pharmacokinetics: what the body does to a drug
• Drug: any single synthetic or natural substance of known structure used in the treatment, prevention or diagnosis of disease
• Medicine: chemical preparation containing one or more drugs; therapeutic effect
• Selectivity: the ability of a drug to distinguish between different molecular targets within the body

Agonists and antagonists

• Agonist: drug that binds to a receptor to produce a cellular response
  • Temporarily activate receptors by producing a conformational change
  • Possess affinity and efficacy
• Affinity: strength of association between ligand and receptor (binding)
• Efficacy: ability of an agonist to evoke a cellular response (activation)
• Antagonist: drug that reduces, or blocks, the actions of an agonist by binding to the same receptor – do not activate them
  • Possess affinity but lack efficacy

Potency and efficacy

• Potency: amount of drug required to produce a desired effect
• Efficacy: maximum response achievable from drug

EC50

• Concentration of agonist that elicits half maximal effect
• Easy to see using semi-logarithmic plot of concentration vs. effect - sigmoidal relationship

Competitive and non-competitive antagonism