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Brain Anatomy > PHAR232 - Weeks 1 & 2 > Flashcards

PHAR232 - Weeks 1 & 2 Flashcards

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1
Q

define pharmacokinetics

A

the study of how a drug is absorbed, distributed, metabolized, and excreted by the body.

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2
Q

Define pharmacodynamics

A

the study of how a drug interacts with the body and produces its effects.

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3
Q

What are the key targets of pharmacodynamics?

A

-Receptors
- Enzymes
- Voltage-gated ion channels
- Uptake/transport proteins
- Other cellular constituents

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4
Q

What is the key issue with pharmacodynamics?

A

Specificity e.g. one target or many

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5
Q

What is a drug specificity?

A

Drug has single action at a tissue or organism level

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6
Q

What is drug selectivity?

A

Ability for a drug to affect one type of cell, leaving another virtually untouched (usually distinguishes between receptors and subtype receptors)

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7
Q

What are 3 the types of agonists e.g. activators?

A

» agonists (= true agonists)
» partial agonists
» inverse agonists

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8
Q

what are the 4 types of antagonists (blockers/inhibitors)

A

Competitive antagonist: Competes with the agonist for binding to the same receptor site, reducing the agonist’s ability to activate the receptor.

Non-competitive antagonist: Binds to a different site on the receptor than the agonist, resulting in a conformational change that reduces the receptor’s response to the agonist.

Allosteric antagonist: Binds to an allosteric site on the receptor, leading to a conformational change that affects the receptor’s ability to respond to the agonist.

Partial agonist: Binds to the receptor and activates it to a lesser extent than a full agonist, producing a submaximal response even when all receptors are occupied.

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9
Q

can antagonists change
physical conformation of a receptor?

A

No

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10
Q

Define drug affinity meaning

A

ability of drug to bind receptor

» is it easy? is it hard? is it influenced by cofactors or mediators?

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11
Q

What does a drug efficacy relate to?

A

» ability to activate receptor (fully? partially?)
to elicit effect (response)
» degree to which agonist exerts an
effect

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12
Q

What is a drug potency mean?

A

» range of concentrations required to have impact
» if low concentration of drug needed for maximal effect, then drug has high potency

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13
Q

What are 3 key features that an agonist has to have to change receptor conformation and activate it?

A

» affinity
» efficacy
» potency

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14
Q

What is allosteric modulation?

A
  • molecule binds to a specific site on receptor or enzyme,(known as an allosteric site)
  • Causes confirmational change
  • either enhances (positive allosteric modulation) or inhibits (negative allosteric modulation) function
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15
Q

Define partial agonists

A

agonists unable to fully change receptor (target) conformation = partial agonists

maximum effect never achieved with partial agonist

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16
Q

what is an inverse agonist?

A

drugs that interact with receptor to create non-active conformational change e.g. can create altered conformation that ensure
receptor stays inactive

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17
Q

what is constitutive activity>

A

receptor “works” in
absence of ligand (i.e.
receptor always “on”)

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18
Q

What are 3 key features of an antagonist drug?

A

= occupies receptor to prevent
agonist-triggered activation
* has affinity not efficacy
* do not change receptor conformation

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19
Q

What are 3 different types of antagonists

A
  • competitive antagonists
  • non-competitive antagonists
  • irreversible antagonists
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20
Q

How does a competitive antagonist work?

A

binds to same place on target as
agonist & therefore, competes for binding

21
Q

What are 2 examples of competitive antagonists?

A
  • Beta blockers
  • Anti-histamines
22
Q

What are 2 mechanisms to which non-competitive antagonists work?

A
  • Binding to a different part of a receptor
  • Binding to different coponent in signalling chain that allows agonist to exert its effect

NOTE: agonist will not be able to exert maximal
effect no matter how much agonist is added

23
Q

What is an example of a non-competitive antagonist?

A

Ketamine

24
Q

How does ketamine exert a non-competitive antagonist affect?

A

ketamine = polyamine
antagonist of NMDA glutamate
receptor

  • does not compete with
    glutamate for binding
    – has its own site
25
Q

Define Irreversible Antagonists

A

+ binds to target molecule & either cannot be removed or
+ can only be removed with difficulty

  • removal of drug requires destruction of receptor
26
Q

By what 3 mechanisms do irreversible antagonists cause an affect?

A

– decreases total number of available targets for agonist to bind over prolonged period

» decreases maximum possible response of agonist

– time delay to restoration of full tissue potential due to requirement for synthesis of
replacement proteins

27
Q

What is chemical antagonism?

A
  • agonist becomes physically bound to chemical
    antagonist & removed from availability
  • therefore, agonist is incapable of interacting
    with target & therefore effect is reduced
28
Q

What is an example of chemical antagonism?

A

ion resin cholesterol-lowering
drugs & chelating agents

  • ion exchange resin (e.g. cholestyramine) binds
    cholesterol in gut preventing absorption
29
Q

What is the goal of Pharmacokinetic Antagonism?

A

remove agonist from system more quickly reducing its ability to reach target & exert effect:

  • promoting agonist elimination, or
  • altering agonist distribution

» therefore, changes pharmacokinetics of drug
» e.g. changes drug half-life

30
Q

What is Physiological Antagonism?

A

competition between 2 opposing systems in
the body

31
Q

What are 4 key elements that defines a drug pharmacokinetics?

A
  • Absorption
  • Distribution
  • Metabolism
  • Elimination
32
Q

Learning Objectives – How Drugs Act 1 & 2

By the end of this week, you should be able to:
* identify the routes of administration of drugs;
* discuss the implications for the organism of the different routes of administration;
* discuss the impact of common medical conditions on the route of administration of drugs;
* differentiate between the two main branches of pharmacology, namely pharmacodynamics and pharmacokinetics;
* define the key characteristics of drug action, namely affinity, efficacy and potency;
* apply the key characteristics of drug action to novel situations involving data and clinical scenarios;
* define true agonist, inverse agonist, partial agonist;
* apply definitions of agonists to novel situations involving data and clinical scenarios;
* define competitive antagonist, non-competitive antagonist and irreversible antagonist;
* apply the definitions of antagonist to novel situations involving data and clinical scenarios;
* define physiological antagonism, pharmacokinetics antagonism and chemical antagonism; and
* apply the definitions of antagonism to novel situations involving data and clinical scenarios.

A
33
Q

identify the routes of administration of drugs;

A
  • Oral
  • Sublingual
  • Inhalation (gases, vapors, aerosols)
  • IV
  • Intramuscular (IM)
  • Subcutaneous (fatty tissue injections)
  • Transdermal
  • Rectal
  • Intranasal (Sprays, drops)
34
Q

Define drug affinity

A

the ability of a drug to bind to its specific target, such as a receptor, with a high degree of selectivity and strength.

35
Q

Define drug efficacy

A

represents the drug’s capacity to produce a desired effect or response upon binding to its target, typically measured by the maximum effect it can produce.

36
Q

Define drug potency

A

Potency relates to the concentration or dose of a drug required to produce a specific effect, reflecting its relative strength or activity in achieving the desired response.

37
Q

UNDERSTAND HOW BETA BLOCKERS WORK

A

LOOK AT PHYSIOLOGY

38
Q

What foes “shift to the right” mean ?

A

Means more AGONIST required for response if ANTAGONIST is present.

It takes more DRUG to get my original response if an antagonist is present.

39
Q

What are examples of competitive antagonists?

A

Beta blockers
anti-histamines

40
Q

What is a key element of a non-competitive antagonist?

A

An AGONIST will NOT be able to exert MAXIMAL EFFECT no matter HOW MUCH agonist is added

41
Q

What is a key similarity between irreversible antagonists and non-competitive antagonists?

A

Shapes of the curves on dose-dependent are identical to non-competitive and irriversible antagonists.

You will not be able to differentiate what antagonist it is based on the curvature. Both will have curves that look the same.

42
Q

How would you be able to differentiate between an irreversible antagonist and a non-competitive antagonist?

A
  • Drug disassociation times from binding essays (irreversibles will NOT unbind)
  • Structural analysis of drug-recepter interactions (how many receptors are occupied)
43
Q

How would you describe antagonism?

A

It’s the PROCESS

44
Q

Chemical antagonism

A
  • Doesn’t care about the enzyme/receptor
  • Cares about the DRUG it wants to antagonise
  • AGONIST becomes physically bound to ANTAGONIST and removed from availability
45
Q

What is pharmacokinetic antagonism?

A

GOAL: remove agonist from the SYSTEM more quickly
- promotes agonist ELIMINATION
- alters agonist DISTRIBUTION
- changes drug HALF LIFE
- e.g. alcohol and warfarin - alcohol increases P450 enzyme for drug elimination (reduces total warfarin effect)

46
Q

Pharmacokinetic antagonism example: ST JOHNS WORT

A
47
Q

How many estimated cytochrome P450 mono-oxygenases have been established?

A

74 genes identified

48
Q

What is physiological antagonism ?

A
  • Competition between 2 opposing systems in the body
    e.g. beta blockers (lower BP) and muscarinic antagonist (increases BP)

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