Pharmacodynamics - Part 1: How Drugs Act on the Body

Pharmacodynamics: Understanding Drug Action

Introduction to Pharmacodynamics

• Pharmacodynamics explores how drugs affect the body, focusing on their effects at specific sites of action.

• Unlike pharmacokinetics, which examines how the body processes drugs, pharmacodynamics looks at drug interactions with receptors and enzymes.

Mechanisms of Drug Interaction

• Drugs are categorized as agonists (activators) or antagonists (inhibitors), influencing biochemical processes without initiating new ones.

• The discussion will center on drug-receptor interactions rather than other mechanisms like DNA interaction or osmotic balance.

Types of Agonists and Antagonists

• Agonists can be direct (mimicking endogenous signals) or indirect (enhancing natural signaling).

• Antagonists are classified into competitive (binding to the same site as signaling molecules) and non-competitive (binding elsewhere but altering receptor shape).

Functional Antagonism Explained

• Functional antagonists bind to receptors and promote reactions that counteract downstream physiological processes.

• Adrenaline serves as an example; it acts against histamine-induced vasodilation without competing for the same receptor.

Role of Partial Agonists