Drug Mechanisms
Major classes of drug mechanisms explaining how pharmaceuticals interact with biological targets.
Enzyme Inhibitors
Enzyme inhibitors block the active site of a specific enzyme, preventing it from catalyzing its normal biochemical reaction. This reduces the production of a downstream product or prevents the breakdown of a substrate. Inhibition can be competitive (competes for the active site), non-competitive (binds an allosteric site), or irreversible (permanently modifies the enzyme).
Example Drugs
Receptor Agonists
Receptor agonists bind to and activate a cellular receptor, mimicking the action of the body’s natural signaling molecules. They trigger the same intracellular cascade as the endogenous ligand, producing a pharmacological response. Agonists can be full (maximal response), partial (submaximal response), or inverse (opposite response).
Example Drugs
Receptor Antagonists
Receptor antagonists bind to a receptor without activating it, thereby blocking the binding of the natural agonist. This prevents the normal signaling cascade from occurring. Antagonists can be competitive (reversibly occupy the binding site) or non-competitive (bind irreversibly or at an allosteric site).
Example Drugs
Ion Channel Modulators
Ion channel modulators alter the function of ion channels in cell membranes, affecting the flow of ions such as Ca²⁺, Na⁺, and K⁺. By blocking or opening these channels, they modulate membrane potential, muscle contraction, nerve conduction, and cardiac rhythm.
Example Drugs
DNA Intercalators / Alkylating Agents
These agents directly modify DNA structure, either by inserting (intercalating) between base pairs or by forming covalent crosslinks between DNA strands. This prevents DNA replication and transcription, triggering cell death. They are primarily used in cancer chemotherapy where rapidly dividing cells are the target.
Example Drugs
Antimetabolites
Antimetabolites are structural analogs of natural substrates involved in DNA and RNA synthesis. By mimicking these molecules, they are incorporated into metabolic pathways where they block or disrupt normal nucleic acid production. This halts cell division, making them effective against rapidly proliferating cancer cells.
Example Drugs
Antibiotics (Protein Synthesis Inhibitors)
These antibiotics target bacterial ribosomes, which differ structurally from human ribosomes, providing selective toxicity. By binding to either the 30S or 50S ribosomal subunit, they block bacterial protein synthesis at various stages — initiation, elongation, or translocation — leading to bacteriostatic or bactericidal effects.