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FPP Pharmacology > Intro Pharmacodynamics > Flashcards

Intro Pharmacodynamics Flashcards

1
Q

Pharmacodynamics is the study of the ______ and __________ effects of drugs and their ___________ of ___________

A

biochemical
physiological
mechanisms of action

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2
Q

Simply put, pharmacodynamics is?

A

The effects of drug on the body

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3
Q

What is the 2 STATE RECEPTOR MODEL

A

A receptor may exist in two interchangeable states, active (Ra) & inactive (Ri) which are in equilibrium.

Binding of drug shift this equilibrium in either direction

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4
Q

What is a ligand?

A

any molecule which attaches selectively to particular receptors.

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5
Q

Define affinity

A

Affinity is the strength of the reversible interaction between a drug and its receptor

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6
Q

Affinity is measured by

A

Dissociation constant

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7
Q

What is intrinsic activity?

A

The capacity to induce a functional change in the receptor

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8
Q

A drug that interacts with a single type of receptor that is expressed on only a limited number of differentiated cells is exhibiting?

A

High specificity

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9
Q

What are agonist?

A

Drugs that bind to physiological receptors and mimic the regulatory effects of the endogenous signaling compounds

They have affinity and intrinsic activity therefore maximal effect

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10
Q

If a drug binds to the same recognition site as the endogenous agonist (the primary or orthosteric site on the receptor) the drug is said to be a

A

Primary agonist

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11
Q

Allosteric agonists….

A

bind to a different region on the receptor referred to as an allosteric site.

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12
Q

Why would a drug be called an antagonist?

A

If it blocks or reduces the action of an agonist

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13
Q

5 types of Antagonists

A

Physical
Chemical
Physiological
Partial
Inverse

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14
Q

Physical antagonists…

A

… binds to the drug and prevents its absorption

like charcoal binds to alkaloids and prevents their absorption.

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15
Q

Chemical antagonists…

A

combines with a substance chemically

like chelating agents binds with metals

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16
Q

What is the mode of operation of physiological antagonist

A

They produces an action opposite to a substance but by binding to the different receptors

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17
Q

How is adrenaline a physiological antagonist of histamine?

A

adrenaline causes bronchodilatation by binding to β2 receptors, which is opposite to bronchoconstriction caused by histamine through H1 receptors

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18
Q

What are partial agonists?

A

Agents that are only partly as effective as agonists regardless of the concentration employed.

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19
Q

Many receptors exhibit spontaneous activity in the absence of a regulatory ligand; drugs that stabilize such receptors in an inactive conformation are termed

A

Inverse agonists

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20
Q

Inverse agonists produce effects that are

A

Opposite to that of agonist

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21
Q

What is efficacy

It can only be measured with?

A

A maximal effect (Emax) an agonist can produce.

A graded dose-response curve

22
Q

What is potency

A

The amount of the drug needed to produce a given effect.

23
Q

Potency is determined by?

A

the affinity of the receptor for the drug.

24
Q

The dose causing 50% from the maximal effect (EC50) can be obtained from

A

graded dose-response curve.

25
Q

In what curve are ED50, TD50 and LD50 are potency variables?

A

Quantal dose response curve

26
Q

Tolerance is

A

Repeated administration of a drug resulting in diminished effect

27
Q

2 types of Tolerance & define

A

Tachyphylaxis: is a type of tolerance which occurs very rapidly.

Desensitization: decreased response to the agonist after its repeated injection in small doses.

28
Q

Tolerance can be due to 3 things. What are they?

A
  1. Masking or internalization (endocytosis) of the receptors

2- Loss of receptors (down regulation)- decreased synthesis or increased destruction

3- Exhaustion of mediators (depletion of catecholamine).

29
Q

Difference between competitive and non competitive antagonist 7

A

Antagonist binds with the same receptor as the agonist
2. Antagonist resembles chemically with the agonist
3. Parallel rightward shift of agonist DRC
4. The same maximal response can be attained by increasing dose of agonist (surmountable antagonism)
5. The antagonist appears to have inactivated a certain number of agonist molecules
6. Intensity of response depends on the concentration of both agonist and antagonist
7. Examples: ACh-Atropine
Morphine-Naloxone

Noncompetitive
1. Binds to another site of receptor
2. Does not resemble
3. Flattening of agonist DRC
4. Maximal response is suppressed (unsurmountable antagonism)
5. The antagonist appears to have inactivated a certain number of receptors
6. Maximal response depends only on the concentration of antagonist
7. Diazepam–Bicuculline

30
Q

What is synergism?

A

When the action of one drug is facilitated or increased by the other, they are said to be synergistic.

31
Q

In a synergistic pair,….

A

both the drugs can have action in the same direction or given alone one may be inactive but still enhance the action of the other when given together.

32
Q

In additive drug combinations

A

The effect of the two drugs is in the same direction and simply adds up

effect of drugs A + B = effect of drug A + effect of drug B

33
Q

Types of additive drug combinations 5

A

Aspirin + paracetamol= as analgesic/
antipyretic

Nitrous oxide + halothane =as general
anaesthetic

Amlodipine + atenolol = antihypertensive

Glibenclamide + metformin = hypoglycaemic

Ephedrine + theophylline = bronchodilator

34
Q

What is super additive drug combination/ potentiation

A

The effect of combination is greater than the individual effects
of the components:
effect of drug A+ B > effect of drug A+ effect of drug B

This is always the case when one component is inactive as such

35
Q

Examples of super additive

A

Pics

36
Q

Characteristics of competitive antagonist 6

A

Same binding site as of agonist
•resembles chemically with agonist
•Right shift of DRC
•Surmountable antagonism by increasing agonist dose
•Inactivation of certain agonist molecules
•Response depends on concentration of both
e.g Ach – Atropine, Morphine - Naloxone

37
Q

Characteristics of non competitive antagonist 6

A

Different binding site as of agonist.
•Not resembles chemically with agonist.
•Flattening/downward shift of DRC.
•Unsurmountable antagonism (Maximum response is suppressed).
•Inactivation of certain receptors.
•Maximum response depends on concentration of antagonist
e.g. Diazepam - Bicuculline

38
Q

6 examples of physiological receptors

A

GPCR
•Ion channels
•Transmembrane enzymes
•Transmembrane, non-enzymes
•Nuclear receptors
•Intracellular enzymes

39
Q

2 major functions of physiological receptors

A

Ligand binding

Message propagation (signaling)

40
Q

The regulatory actions of a receptor may be exerted on these 3 things

A

directly on cellular target(s),

on effector protein(s)

may be conveyed by intermediary cellular signaling molecules called transducers.

41
Q

Which signal transduction pathway is fastest and without intervention of G protein or second messenger with examples

A

Ion channels (Ligand gated ion channels)

GABA a, 5HT3, NMDA

42
Q

__________ are signal transducers that convey the information that agonist is bound to the receptor from the receptor to one or more effector proteins.

A

G proteins GPCRs(G protein coupled receptor)

43
Q

The G protein heterotrimer is composed of 3 things. These are?

A
  1. a guanine nucleotide-binding α subunit, which confers specific recognition to both receptors and effectors

2&3 an associated dimer of β and ϒ

44
Q

G protein effectors include enzymes like 4

A

Adenylyl Cyclase
Phospholipase C
Cyclic GMP phosphodiesterase
Membrane ion channels selective for Ca & K+

45
Q

GPCR characteristics 3

A

GPCRs span the plasma membrane as a bundle of seven alfa-helices.

•Extracellular binding site for ligand.

•Cytosolic binding site for transducer G-protein.

46
Q

Adenylyl cyclase

A

Increase in cAMP - Protein kinase A phosphorylation -

Increase in heart contraction
Smooth muscle relaxation
Glycogenolysis
Lipolysis
Inhibition of secretion

47
Q

Phospholipase C pathway

A

Phosphatidyl inositol biophosphate (PIP2) - IP3 + DAG
IP3 - mobile calcium ions
DAG- PKc activation

Contraction
Neural excitation
Cell proliferation

48
Q

Steps of resensitization and down regulation of receptors

A

Agonist binding to receptors initiates signaling by promoting receptor interaction with G proteins (Gs) located in the cytoplasm.

  1. Agonist-activated receptors are phosphorylated by a G protein-coupled receptor kinase (GRK), preventing receptor interaction with Gs and promoting binding of a different protein, - β arrestin (β-Arr), to the receptor.

3.The receptor- β arrestin complex binds to coated pits, promoting receptor internalization.

4.Dissociation of agonist from internalized receptors reduces - β Arr binding affinity, allowing dephosphorylation of receptors by a phosphatase.

5.Return of receptors to the plasma membrane result in the efficient resensitization of cellular responsiveness

  1. Repeated or prolonged exposure of feels to agonists favors the delivery of internalized receptors to lysosome, promoting down regulation rather than resensitization
49
Q

Enzyme linked receptors are of 2 forms

A

With intrinsic enzymatic activity.

•Without intrinsic enzymatic activity but associated with an enzyme usually a kinase (bind a JAK-STAT kinase on activation)

50
Q

Viagra is also known

A

Sidenafil

FPP Pharmacology (11 decks)

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