L15 Dynamics Of Drug Action Flashcards

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1
Q

What is major target of drug action

A

Cell surface receptors or intracellular and sometimes some membrane transporters

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2
Q

Explain mechanism of Drugs modulating ligand gated ion channels (metabotroptic receptors)

A

Bind instead of ligand and alter flow of ions passing in to channels

a) inhibition of influx of NA and efflux of K in response to activation of nicotinic receptors(help in muscle relaxation during operations)
b) stimulation of influx of chloride in response to GABA receptor A to suppress neuronal functions (help in convulsions)

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3
Q

Explain mechanism of drugs modulating G protein coupled receptors

A

Bind instead of ligand
Ignite or switch off transduction cascade
Cascade is initiated by specific G protein and 2ndry messengers and affect many downstream hormones

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4
Q

What are drugs modulating G protein coupled receptors mainly triggered by

A

Gs proteins linked to B2 adrenergic receptors to activate adenylate cyclase and inc cAMP to activate protein kinase A to induce bronchodilation in bronchial asthma

Gi linked to a2 adrenergic receptors to inhibit AC and dec cAMP and inhibit PKA reducing blood pressure in hypertension

Gq linked to a1 adrenergic receptors to activate PLC Increasing IP3 and DAG activating PKC to inc blood pressure in hypotension

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5
Q

Explain mechanism of drugs modulating enzyme linked receptors

A

They can:
Bind to receptor instead of ligand to activate or inhibit down stream receptor activation of exogenous insulin to stimulate intrinsic tryosine kinase receptor (controls type 1 more than type 2)

Bind to ligand itself to prevent activation of receptors during use of anti-TNFa(mAb) to control rheumatoid or IBD

Bind to downstream signaling of the receptor directly as when immune modulators is used to treat some cancers

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6
Q

Drug affinity

A

Shows how well a drug recognizes and binds to its receptor

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7
Q

Drug potency

A

Measures the required amount of drug necessary to produce an effect of a given intensity when reaching and binding with variable affinity to its receptor

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8
Q

Drug efficacy

A

Measure effectiveness of a drug to elicit a max achieved response when given at highest practical concentration

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9
Q

Antagonist

A

When drug fails to elicit any desired response and meanwhile prevents endogenous ligand from binding to the receptor

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10
Q

Agonist

A

When a drug binds to its receptor and formed bound complex elicits a desired response (has affinity and efficacy)

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11
Q

When is s shaped curve called

A

Graded dose response curve

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12
Q

What is Max concentration called and what does it show

A

E max

Efficacy

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13
Q

Half maximal response

A

EC50

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14
Q

When is potency of drug considered high

A

If effect of a given intensity is evoked by a small dose of a drug

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15
Q

Types of agonists

A

Full
Partial
Inverse

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16
Q

What is a full agonist

A

Mimics response of ligand (has same efficacy)

17
Q

What is a partial agonist

A

Incapable of reaching response of ligand (has lower efficacy) and is giving sub maximal response

18
Q

What is an inverse agonist

A

Stabilizes a spontaneously activated receptor setting it back to its inactive state

19
Q

Types of antagonists

A

Competitive reversible
Competitive irreversible
Non competitive antagonist

20
Q

Whats a competitive reversible antagonist

A

Binding is non permanent and can be overcome by increasing concentration of agonist relevant to it

21
Q

What is a competitive irreversible antagonist

A

Binding is permanent because it forms a covalent bond with the active site
Cannot be overcome by inc concentration

22
Q

What is a non competitive antagonist

A

Blocking agonist ability to activate its receptor by binding to a diff site (allosteric site)

23
Q

Whats physiological antagonism

A

Achieving antagonistic effect by acting on a diff receptor (ex: adrenaline that induces vasoconstriction by action a1 adrenergic receptors to antagonize vasodilator action of histamine produced by its action of H1 receptors)

24
Q

What is chemical antagonism

A

Achieving antagonistic effect by reacting chemically to form an inactive complex
(Ex: protamine sulphate that forms an inactive complex with heparin when there is no need to stop hemorrhage induced by it)