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1. Pharmacology-1 PHL 211
11. II. Non-receptor Mechanisms Actions on Enzymes
Enzymes = Biological catalysts
Speed chemical reactions
Are not changed themselves
Some drugs alter enzyme activity & alter processes catalyzed by the enzymes
Examples
Cholinesterase inhibitors
Monoamine oxidase inhibitors
12. Changing Cell Membrane Permeability (Ion Channels)
Lidocaine (a local anesthetic)
decreases permeability of the nerve cell membrane to NA+ ? the rate of depolarization of the nerve membrane, threshold for electrical excitability, & propagation of the action potential
Verapamil & nefedipine (calcium channel blockers)
Block calcium channels ? Ca influx into smooth and cardiac muscle ? vasodialate vascular smooth muscle & myocardial contractility, slow AV nodal conduction
Adenosine (an inhibitory neurotransmitter)
Opens potassium channels
13. Anti-metabolites
An anti-metabolite is a chemical with a similar structure to a substance (a metabolite) required for normal biochemical reactions, yet different enough to interfere with the normal functions of cells, including cell division
Examples:
Anti-neoplastics e.g., 5-FU (5-fluorouracil) ? inhibits RNA synthesis
Antimicrobials such as sulfonamide drugs, which inhibit dihydrofolate synthesis in bacteria by competing with para-aminobenzoic acid (PABA)