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MECHANISM OF DRUG ACTION By. Jyotirmoy Das Choudhury M.Pharm 2nd semester Phamacology Under the Guidance of Miss. Saiprasanna Behera (M.Pharm), Lecturer, Pharmacology Department. RCPHS

Content… : 

Content… Definition Factors Affecting the Drug Action Different Mechanism of Drug Action Recent Advances Reference

Definition… : 

Definition… Drug Action: Drug action is the initial interaction of a drug with cells at the site of action & the resultant physiological & biochemical consequences are the drug effect.

Factors affecting Drug Action : 

The drug action & drug effects depends upon the drug concentration achieved at the site of action. Which is determined by: Absorption of drug after oral or parenteral administration First pass metabolism Biotransformation Excretion Tissue affinity Condition of the body Factors affecting Drug Action

Different Mechanism of Drug Action…. : 

Different Mechanism of Drug Action….

Physical Properties.. : 

Physical Properties.. Colour: A pleasant colour may exert a physiological effect, e.g. tincture of cardamom. Physical Mass: Isaphgul. Smell: Volatile oil like Peppermint oil are used to mask the unpleasant smell of mixture. Taste: Bitter tasty compounds helps to improve apatite by secreting HCl. Osmolality: Osmotic diuretics like Mannitol. Adsorption: Kaolin & activated charcoal Soothing- demulcent: Calamine lotion in eczema.

Cont…. : 

Reduction in surface tension: Cationic surfactant s like Cetrimide for cleaning the skin Electrical Charge: Heparin is strongly acidic in nature, exerts its anti coagulant effect by virtue of its negative charge Radioactivity: I131 in the treatment of hyperthyroidism Radio-opacity: Iodide compound for the visualisation of the urinary & biliary tract. Cont….

Chemical Properties.. : 

Acidity or Alkalinity: Antacids in the treatment of peptic ulcer Chelation: The chelating agent forms a ring structure with the molecules of leads, Cu & other metal. This ring structure is non-toxic & water soluble & is excreted through urine. Chemical Properties..

Modulating body function regulator... : 

NEUROTRANSMITTERS, HORMONES & GROWTH FACTOR: Drugs may resemble neurotransmitters, hormones or growth factor, binds to the specialized constituents of cell & mimic or oppose their action Drugs may act as a replacement when the production of endogenous substances decrease. e.g. Insulin in DM, Hydrocortisone in Addison’s disease Modulating body function regulator...

Cont…. : 

Drug may interfere with NT uptake. e.g. SERT, the transporter for serotonin, is a target for the antidepressant Fluoxetine which inhibits the reuptake of serotonin & increases its concentration in synapse. Cont….

Cont…. : 

Enzymes: Drugs may act by either increasing the rate of enzymetically mediated chemical reaction in the body or by decreasing such rate. Enzyme stimulation by drugs, which are foreign substances are unusual; it occurs mainly with endogenous substances like hormones. e.g. Adrenaline stimulates adenylyl cyclase Enzyme inhibition occurs commonly with drugs. e.g. Ramipril inhibits ACE Cont….

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Cont…. : 


Cont…. : 

Transport processes: Various transport processes such as Na+ K+ ATPase pump, Ca++ channels, K+ channels etc. regulates the ionic concentration of the cells & controls the cell functions. Drugs may bind to these Pumps or Channel to alter the cell activity. E.g. Verapamil blocks the Ca++ channel, Minoxidil is K+ channel opener. Cont….

Cont…. : 

Structural Proteins: Drugs may also bind to the structural proteins of the body. E.g. Cyclosporin, an immunosuppressant binds to immunophillins. Other cell constituents like DNA: Many antiviral & anticancer drugs are structural analogs of nucleic acid & compete with them to get incorporated in cellular RNA or DNA, interfering with cellular division or growth, eg. Folic acid antagonist Methotrexate. Cont….

Receptor binding.. : 

Receptor binding..

Recent Advances... : 

Recent Advances... GPCR oligomerization:- new targets for drug development. Signaling by internalized GPCR.

References... : 

R.S. Satoskar, S.D. Bhandarkar, Nirmala N. Rege; Pharmacodyanamics – Drug Receptor Interaction; 21st Edition; 2009; Page : 28 – 29. K.D. Tripathi; Pharmacodyanamics: Mechanism of Drug Action; Receptor Pharmacology; 6th Edition; 2008; page: 38 – 41. References...

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