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AUDE 6120 - Pharmacology and Ototoxicity > Pharmacodynamics > Flashcards

Pharmacodynamics Flashcards

1
Q

What is pharmacodynamics?

A

Describes the effects of a drug on the body
Study of the biochemical and physiologic actions of drugs and mechanisms of drug action at the molecular, cellular, tissue (organ), and organism (patient) level

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2
Q

Why are effects described in quantitative terms?

A

To determine appropriate dose ranges
To compare potency, efficacy, and safety of one drug to another

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3
Q

What does the drug do after it has been distributed to its site of action?

A

It elicits a pharmacologic effect
This effect occurs because of a change in the function of the cell/organism

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4
Q

What do drugs do if they do not impart new functions?

A

They either produce the same action as the body’s own chemicals or it blocks the action of the body’s own chemicals

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5
Q

Do drugs or ligands bind to receptors at a cellular level to bring about a drug action?

A

Yes

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6
Q

What is a ligand?

A

An extracellular molecule, such as an antibody, hormone, neurotransmitter, or drug, that binds to a receptor

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7
Q

Do most drugs interact with receptors?

A

Yes

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8
Q

What are receptors?

A

A specialized target molecule that binds a drug and mediates its pharmacological action; the formation of the drug-receptor complex leads to a biological response

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9
Q

Where are receptors present?

A

On the outside of the cell membrane
Inside of the cell membrane
Span both sides of the cell membrane

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10
Q

Can a single cell have hundreds of receptor sites?

A

Yes

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11
Q

What are the different receptor sites that can be on a single cell?

A

Metabolic or regulatory enzymes
Proteins or glycoproteins associated with cell transport mechanisms
Structural and functional components of the cell membrane
Nucleic acids

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12
Q

Is the study of pharmacodynamics based on the concept of drug-receptor binding?

A

Yes

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13
Q

When a drug or an endogenous ligand binds to its receptor, does a response result from the binding action?

A

Yes

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14
Q

What are the two ways a receptor can be bound to a drug?

A

Free (unoccupied) or reversibly bound (occupied)

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15
Q

When a sufficient number of cell receptors are bound (occupied), what happens?

A

The cumulative effect of receptor occupancy may become apparent in that cell
Resulting in the maximal desired response of the interaction
When this response occurs, the effect can be apparent in the organ and/or the patient

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16
Q

How do drugs attach to or interact with receptor sites?

A

Covalent, ionic, hydrogen, hydrophobic, or Van der Waals bonding to produce a definable pharmacological response

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17
Q

What types of bonds are most common for receptor sites?

A

Hydrogen and ionic
Require little energy and may be easily broken

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18
Q

Is the affinity of a drug for a particular receptor and the type of binding intimately related to the drug’s chemical structure?

A

Yes

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19
Q

What can an increase in the effect of a drug result from?

A

Increase in the concentration of either the ligand or the receptor

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20
Q

What is the lock and key model?

A

In this analogy, the lock is the enzyme (receptor) and the key is the substrate (drug molecule)
Only the correct key (drug) fits into the key-hole (active site) of the lock (receptor)

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21
Q

What is the induced fit model?

A

Drug molecule doesn’t have to fit exactly, receptor will adapt to it
You have a little bit more flexibility than the lock and key model

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22
Q

What assumptions are made for the induced fit model to work?

A

Assumes that substrates (drug molecules) plays a role in determining the final shape of the receptor and the receptor is partially flexible

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23
Q

What are G proteins?

A

They are involved in transmitting signals from a variety of stimuli outside a cell to its interior in many important processes
Bring about a change inside the cell
Involved in vision, olfaction, and neurotransmission
Activate production of secondary messengers that convey input provided by the first messenger to cytoplasmic effectors (involved in signaling) (bring about action)

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24
Q

Why are G proteins called G proteins?

A

They bind the guanine nucleotides GDP (guanine-dinucleotide proteins) and GTP (guanine-trinucleotide proteins), and are a family of proteins that act as molecular switches inside cells

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25
Are G proteins the most abundant class of cell receptors in the human body?
Yes
26
What is G proteins activity regulated by?
Factors that control their ability to bind to and hydrolyze guanosine triphosphate (GTP) to guanosine diphosphate (GDP) When they are bound to GTP, they are ‘on,’ and when they are bound to GDP, they are ‘off’ (the signal is terminated)
27
Do G proteins belong to a larger group of enzymes?
Yes, it is called GTPases
28
What do ion channels do?
They regulate the passage of ions and other hydrophilic molecules across the plasma membrane
29
What is the function of ion channels?
Diverse functions Including fundamental roles in neurotransmission, cardiac conduction, and muscle contraction
30
Do drugs that target ion channels have a significant impact of major body functions?
Yes
31
Are channels highly selective for the ions they conduct?
Yes
32
What is cell signaling?
Receiving and interpreting signals from their environment Signals can come in the form of light, heat, chemicals (neurotransmitters), water, odors, touch, and/or sound
33
Can cells of multi-cellular organisms receive signals from other cells?
Yes Including signals for cell division, differentiation, and apoptosis
34
Do the majority of cells in our bodies need to constantly be receiving signals that keep them alive and functioning?
Yes
35
Do all organisms have signaling systems that warn them of the presence of pathogens, leading to a protective response?
Yes
36
What is a conformational change?
When signals from receptor activation/inhibition cause functional/structural changes in the cell
37
What are the cells responses to conformational changes?
Ion channel opening or closing Formation of intracellular second messenger Alterations in gene expression of the cell Initiation or alterations in cell growth and differentiation
38
What are the changes in cell function that occur due to a conformational change?
It is the cell’s response to the drug This cell response can be identical, greater, or less than the normal endogenous cell response
39
What are cognates?
Two biomolecules that typically interact A receptor and its endogenous ligand The pharmacological properties of drugs are based on the effects they have on the state of their cognate receptors
40
What is an agonist?
A drug that after binding to its receptor site results in an active conformation Ligands that activate receptors
41
What is an antagonist?
A drug that favors an inactive conformation after receptor binding Stop the action that normally happens in that cell Have no effect in the absence of agonists Beta-receptor antagonists or beta-blockers are drugs that affect heart rate and blood pressure by blocking the effect of norepinephrine (a natural agonist) at its respective binding site on beta receptors
42
Do drugs have a higher affinity for a particular type of receptor?
Yes, they will bind preferentially to that receptor to produce a desired effect
43
Are all neurotransmitters agonists or antagonists?
Agonists to their respective sites
44
Are some NT's excitatory?
Yes, such as acetylcholine and glutamate
45
Are other NT's inhibitory?
Yes, such as GABA
46
Are some NT's excitatory in some tissues and neurons while inhibitory in others?
Yes, such as acetylcholine That may have more to do with the location of the receptor’s activity rather than the neurotransmitter itself
47
Are there drugs that are agonists or antagonists to NT actions?
Yes Example - Triptans are drugs that mimic the effects of Serotonin, and therefore, considered agonists at the 5-HT1-receptor site Triptans 5-HT1-receptor are a mainstay of migraine treatment Serotonin antagonists will block its release and help to prevent nausea
48
Is medication that is used to treat vertigo or meniere's antagonists?
Yes ACh receptor antagonist scopolamine (Transderm scop patch) and meclizine (antivert)
49
Is an antihistamine an antagonist?
Yes It is a antagonist to histamines Benadryl
50
Can some drugs block multiple neurotransmitters?
Yes, like promethazine It exhibits an anticholinergic, antihistamine, and antidopaminergic properties all in one product Used for motion sickness, vertigo, allergies, and has a sedative action
51
Can enzymes and proteins also be targets of drug action?
Yes Ibuprofen, the non-steroidal anti-inflammatory drug (NSAID) inhibits the enzyme cyclooxygenase Cyclooxygenase is needed to create the inflammatory prostaglandins that can form secondary to muscle injury Inflammation can signal pain; therefore, ibuprofen is both an anti-inflammatory and an analgesic
52
What is another drug that inhibits prostaglandins?
Acetylsalicylic acid (Aspirin), one of the first NSAIDs discovered and brought to market
53
What are the two classifications of antagonists?
Receptor antagonists Nonreceptor antagonists
54
What can a receptor antagonist bind to?
Active receptor site, which prevents the binding of an agonist to the receptor Allosteric (not active) receptor site, which prevents the conformational change required for receptor activation (agonists will never act on these)
55
What can receptor antagonists be?
Reversible, those that bind to the receptor site reversibly Irreversible, those that bind to the receptor site irreversibly
56
Do both agonists and antagonists compete for the same receptor site?
Yes If an antagonist binds first, it prevents the agonist from producing its effect This binding can be either competitive or non-competitive
57
What is a competitive antagonist?
Competes with the agonist for the same receptor site and blocks the agonist from binding, maintaining the receptor in its inactive form Competitive binding of the antagonist to the active receptor site is reversible Administering additional agonist displaces the antagonist from the receptor, allowing the agonist to produce its effect
58
What are non-competitive antagonists?
Noncompetitive antagonist can bind to either the active or the allosteric (non-active) receptor site Noncompetitive antagonist bind irreversibly often through covalent bonding They cannot be displaced even with high agonist concentrations Think poisons
59
If an antagonists is bound to the allosteric site, will the receptor activate if an agonist is bound to the receptor?
No, this will prevent receptor activation
60
What is the therapeutic window?
It is the range of doses (concentrations) of a drug that elicit a therapeutic response without unacceptable adverse affects (toxicity) Drugs with a small therapeutic window must be monitored closely (risk of OD is very high)
61
What is the therapeutic index?
A way to quantify the therapeutic window (therapeutic ratio) TI = TD50 ÷ ED50
62
What is TD50?
The drug dose that causes a toxic response in 50% of the population
63
What is ED50?
Drug dose that is therapeutically effective in 50% of the population
64
What does a large therapeutic index indicate?
A large (wide) therapeutic window
65
How can pharmacodynamics of a drug be quantified?
By the relationship between the dose (concentration) of a drug and the organism's (patient's) response (intensity of the effect)
66
What are the two major types of dose-response relationships?
Graded and quantal
67
What is a graded dose-response relationship?
It describes the effect of the various drug doses on an individual
68
What are the two parameters that are important for deducing the graded dose-response relationship?
The potency (EC50) of the drug The efficacy (ECmax) of the drug
69
What is potency (EC50)?
Refers to the concentration at which the drug elicits 50% of its maximal response Potency is related to affinity of a drug to its receptor
70
What is efficacy (ECmax)?
Refers to the maximal response produced by a drug Efficacy is related to receptor occupancy by drug molecules It is the state at which all receptors are occupied by the drug Additional drug will produce no additional benefit/response
71
What is quantal dose-response?
A quantal dose response relationship describes the effect of the various drug doses on a population It plots the fraction of a population that responds to a given dose of a drug against the drug dose It describes the concentrations of a drug that produce a given effect in a population
72
Are quantal dose-responses either present or not present?
Yes Sleep/no sleep Alive at 12 months/not alive at 12 months See an effect or not
73
What is the goal of quantal dose-responses?
To generalize the result to a population rather than examine the graded effects of drug doses on an individual
74
What population responses can be examined using quantal-dose response relationships?
Effectiveness (therapeutic effect) Toxicity (toxic effects) Lethality (lethal dose)
75
What is the median effective dose?
ED50 Dose that produces effectiveness in 50% of the population
76
What is the median toxic dose?
TD50 Dose that produces toxicity in 50% of the population
77
What is the median lethal dose?
LD50 Dose that has a lethal response in 50% of the population

AUDE 6120 - Pharmacology and Ototoxicity (8 decks)

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