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ICS - Pharmacology And Prescribing > Drugs And Receptors > Flashcards

Drugs And Receptors Flashcards

1
Q

Defintion of a drug and routes of administration

A

Medicine or other substance which has either a local or systemic physiological effect
- enteral (GIT - involved e.g oral/PO)
- parenteral (non-GIT e.g IM,IV,SC, injections)
- other (inhaled, topical, rectal)

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2
Q

Pharmacology defintion

A

The branch of medicine concurred with the uses, effects and modes of action of drugs

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3
Q

Name 4 different drug targets

A

Receptors
Enzymes
Transporters
Ion channels

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4
Q

Definition of a receptor

A

A component of a cell that interacts with a specific ligand and initiates a change of biochemical events leading to the ligand observed effects

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5
Q

Example of an exogenous ligand

A

Drugs (extrinsic)

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6
Q

Example of an endogenous ligand

A

Hormones,
Neurotransmitters (intrinsic)

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7
Q

Receptors are the principal means by which chemicals communicate. Give 3 examples of these chemicals with names.

A

Neurotransmitters - acetylcholine, serotonin
Autacoids - cytokines, histamine
Hormones - testosterone, hydrocortisone

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8
Q

Example of when there is an imbalance of chemicals

A

Allergy - increased histamine
Parkinsons - reduced dopamine

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9
Q

Example of when there is an imbalance of receptors

A

Myasthenia gravis - loss of Ach receptors
Mastocytosis - increased c-kit receptors

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10
Q

Types of receptors

A

Ligand-gated ion channels
G-protein coupled receptors
Kinase-linked receptors
Cytosolic/nuclear receptors
Cholinergic receptors

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11
Q

Example of ligand-gated ion channels

A

Nicotinic

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12
Q

Example of a G-protein coupled receptor

A

Beta-adrenoreceptors

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13
Q

Example of a kinase-linked receptor

A

Receptors for growth factors

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14
Q

Examples of cytosolic/nuclear receptors

A

Steroid receptors

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15
Q

How do ligand gated ion channels work?

A

Ion channels are pore-forming membrane proteins that allow ions to pass through the channel pore so that the cell undergoes a shift in electric charge distribution.
The change in charge can be mediated by an influx of any kind of cation or efflux of any kind of anion.

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16
Q

How do g-protein coupled receptors work?

A

Also known as G protein - guanine nucleotide-binding proteins
Their activity is regulated by factors that control their ability to bind to and hydrolyse GTP to GDP
G proteins (GTPases) act as molecular switches (GDO=ON, GTP=OFF)
Targeted by more than 30% of drugs
Ligands include light energy, peptides, lipids, sugars

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17
Q

How do kinase-linked receptors work?

A

Kinases are enzyme that catalyse the transfer of phosphate groups between proteins - process is known as phosphorylation.
The substrate gains a phosphate group ‘donated’ by ATP
Transmembrane receptors activated when the binding of an extracellular ligand causes enzymatic activity on the intracellular side.
They are receptors for growth factors

18
Q

How do cytosolic/nuclear receptors work?

A

Also known as Steroid Hormones
Work by modifying gene transcription

19
Q

How do cholinergic receptors work?

A

There are two categories of cholinergic receptors - nicotinic and muscarinic
Agonist = Muscarinic, Nicotine
Antagonistic = Atropine, Curare
Receptors = mAChR, nAChR

20
Q

Ligand definition

A

A molecule that binds to another (usually larger) molecule

21
Q

Antagonist definition

A

A compound that reduces the effect of an agonist
- full affinity
- ZERO efficacy

22
Q

Agonist definition

A

A compound that binds to a receptor and activates it
- full affinity (how well it binds)
- full efficacy (how well the receptor works)

23
Q

Affinity definition

A

Describes how well a ligand binds to a receptor

24
Q

Efficacy definition

A

Describes how well a ligand activates the receptor
Emax = the maximum response achievable

25
Q

Describe the difference in agonists and antagonists in terms of affinity and efficacy

A

Agonists have affinity and efficacy = but antagonists have affinity and ZERO efficacy

26
Q

What is the two-state model of receptor activation?

A

Describes how drugs activate receptors by inducing or supporting a conformational change in the receptor from off to on.

27
Q

Potency definition

A

The amount of drug that will elicit a 50% response

28
Q

Full activation definition

A

Achieves full activation of pathway

29
Q

Partial agonists defintion

A

Never achieves full activation of pathway

30
Q

Intrinsic activity definition

A

Intrinsic activity (IA) or efficacy refers to the ability of a drug-receptor complex to produce a maximum functional response

31
Q

Two types of antagonists

A

Competitive antagonism - binds to same site
- decreases potency but doesn’t affect the efficacy = ligand conc is rate limiting .
Non-competitive antagonism - binds to an allosteric site on the receptor to prevent activation of the receptor
- decreases both potency + efficacy = ligand conc not rate limiting factor.

32
Q

What is selective agonism?

A

Potency of a range of agonists

33
Q

What are selective antagonists?

A

competitive antagonists

34
Q

Factors effecting drug action?

A

Receptor related - affinity, efficacy
Tissue related - receptor number, signal amplification

35
Q

What is a receptor reserve?

A

Some antagonists need to activate only a small fraction of the existing receptors to produce the maximal system response.
This holds for a full agonist in a given tissue - reserve can be large or small, depends on tissue
No receptor reserve for a partial agonist - even with 100% occupancy, maximal response not seen.

36
Q

What is signal transduction?

A

A basic process involving the conversion of a signal from outside the cell to a functional change within the cell.

37
Q

What is signal amplification?

A

To increase the strength of a signal

38
Q

What is an inverse agonism?

A

When a drug binds to the same receptor as an agonist but induces a pharmacological response opposite to that of the agonist

38
Q

Tolerance definition

A

Reduction in agonist effect over time
Happens when a person is exposed to a drug continuously, repeatedly, and in high concentration

39
Q

Types of desensitisation

A
  • Uncoupled - receptor can’t interact with G-protein
  • Receptor is internalised in vesicle of cell
  • Receptor becomes degraded
    Desensitisation occurs with many agonist drug infusions, perhaps pulsatile
    delivery could avoid this
40
Q

Difference in tolerance to desensitisation

A

Tolerance happens slowly over time, desensitisation is fast

41
Q

Difference between specific and selective

A

Specific drug = acts on a certain target
Selective = acts on a subtype of target e.g cardio selective Bb inhibit B1 adrenergic receptors not B2

ICS - Pharmacology And Prescribing (7 decks)

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