Drug-receptor theories - ANTAGONIST
Drug-receptor interactions- Antagonists
- Created by: Sophie
- Created on: 13-01-13 17:16
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- Drug-receptor theories - ANTAGONIST
- Clinical Uses
- Drug
- Proprolol
- B-antagonist
- antihypertensive
- B-antagonist
- Metaprolol
- B-antagonist
- antihypertensive
- B-antagonist
- Prazosin
- a-antagonist
- antihypertensive
- a-antagonist
- Atropine
- muscarinic antagonist
- Parkinson's Disease
- muscarinic antagonist
- Proprolol
- Drug
- Drug Antagonism
- Chemical antagonishm
- Uncommon
- 2 substances combine in solution; as a result, the effect of active drug is lost
- eg. Dimercaprol binds to heavy metal to reduce toxicity
- eg. Ca/Mg binds to tetracycline antibiotics in gut
- Pharmacokinetic Antagonism
- One drug lowers the concentration of another; antagonish lowers concentration of active drug
- Reduced Absorption
- Increased metabolism
- Increased excretion
- One drug lowers the concentration of another; antagonish lowers concentration of active drug
- Receptor Antagonism
- Antagonist binds to receptor but theres not biological response
- Effect of antagonist is blocked
- Agonist and antagonist can bind to same site
- Some receptors are multi-protein complex
- Agonist or antagonist may bind to diff. proteins or diff. sites on the same protein
- 3 types of receptor antagonism
- Non-competitive
- Antagonist blocks events initiated by agonist
- Antagonist does not bind to same site as agonist
- Irreversible/ Non-equilibrium
- Drug binds to receptor active site but does not dissociate because:
- Covalent Reaction
- Very very slow dissociation
- Active site is occupied by antagonist so agonist cannot bind
- Addition of agonist does not change the no. of receptors occupied by antagonist
- Drug binds to receptor active site but does not dissociate because:
- Competitive
- Most common
- Agonist and antagonist compete for same receptor site
- Reversible binding so dynamic competition
- Drug receptor theory
- 2 equations:
- D + R <=> DR
- A + R <=> AR
- -X response
- Both agonsit (D) and antagonist (A) are present and competing for same binding site on receptor (R)
- -X response
- -> response
- Both agonsit (D) and antagonist (A) are present and competing for same binding site on receptor (R)
- -X response
- A + R <=> AR
- D + R <=> DR
- 2 equations:
- Non-competitive
- Chemical antagonishm
- Clinical Uses
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