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.