Drug-Body Interactions

1. Drug-Body Interactions • Pharmacodynamics = The actions of drug on the body • Pharmocokinetics= The actions of the body on the drug

2. Pharmacodynamic Principles A. Types of Drug-Receptor interactions • Agonists = Bind to, and activate the receptor. e.g.: Opening of an ion channel or activation of enzyme activity. • Antagonists = Prevent binding by other molecules e.g.: Atropine, an acetylcholine receptor blocker

3. Pharmacodynamics (cont’d) B. Duration of Drug Action • Effect of some drugs last only as long as they are bound to the receptor molecule • In other cases, the effect of drugs lasts until a new receptors are synthesized

4. Pharmacodynamics (cont’d) C. Receptors and Inert binding sites Two principles: • The receptor must be selective in choosing ligands (drug molecules) • The receptor must change its function upon binding to cause the pharmacologic effect

5. Pharmacokinetic Principles Involve: • Absorption • Distribution • Permeation • Elimination

6. Mechanisms of Permeation • Aqueous diffusion- intestinal space, cytosol etc • Lipid diffusion – Most important limiting factor of drug permeation because of large number of lipid barriers that separates the compartments of our body • Special Carriers – peptides, amino acids, glucose • Endocytosis and Exocytosis – Large molecules are taken in by endocytosis. Many neurotransmitter substances are stored in membrane bound vesicles. Expulsion into the extracellular space is accomplished by exocytosis

7. Antimicrobial Peptides • Cationic peptides- plants, insects& others • Disrupt plasma membrane integrity • Megainin –from skin of frogs • Squalamine – from spiny dogfish shark • Protegrins – from pigs

8. Antisense Agents • Short segments of synthetic DNA • Selectively recognize and prevent pathogenic protein