Mechanism of Drug Action is very important subject that every dentist needs to be aware of.
Drugs produce their over effects by a variety of fundamental actions:
Outside the cell mechanism of drug action
a. Physical action:
- Colour may exert a psychological effect.
- Smell: Volatile oils like peppermint oil are used to mask the unpleasant smell of mixtures.
- Taste: Compounds with bitter taste improve appetite by reflexively increasing flow of hydrochloride in the stomach.
- Physical mass: Bulk purgatives
- Absorptive property: Kaolin and activated charcoal
- Osmotic activity: Magnesium sulfate, mannitol
- Soothing demulcent: Syrup; calamine lotion
- Radioactivity: 131J and other radioactive isotopes
- Radio-opacity: Contrast media
- Reduction in surface tension: Cationic surfactant
- Electric charge: Heparin is strongly acidic compound. It probably exerts its anticoagulant effect by virtue of its negative charge.
b. Chemical properties:
- Oxidizing agents are germicidal. They inactivate ingested alkalies.
- Antacids neutralize gastric pH.
- Chelating agents form a ring structure with the molecule of metalloid or the metal to give rise a non-toxic and highly water soluble compound. This helps in their excretion in urine.
Mechanism of Drug Action On intracellular constituents
- Enzymes: Monoamine oxidase, cholinesterase, or xanthine oxidase
- Transport carrier molecules, e.g. pro beneci on renal tubules
- Cytosolic or nuclear receptors
- DNA or RNA, e.g. with the use of different anticancer drugs
Antimicrobial Mechanism of Drug Action
- Inhibition of cell wall synthesis, e.g. beta-lactam antibiotics.
- Inhibition of cell membrane function, e.g. polymyxins.
- Inhibition of protein synthesis, e.g. aminoglycosides.
- Inhibition of nucleic acid synthesis and function, e.g. pyrimidine analogues, alkylating agents.
Mechanism of Drug Action on cell membrane
- Action on receptors of agonists and antagonists
- Action on enzymes and pump, e.g. myocardial ATPase and neuronal noradrenaline uptake pumps; adenylyl cyclase enzyme, etc.
- Action on ion channels, e.g. Calcium channel
- Physicochemical interaction with lipid, protein or water constituents of nerve cell membrane, e.g. with general and local anesthetics, alcohol.