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Intro to Pharm > Unit 2 > Flashcards

Unit 2 Flashcards

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1
Q

What is a secondary messenger?

A

a small intracellular signaling molecule that that relay signals from the receptor on the cell surface to target molecules inside the cell

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2
Q

What are some common types of second messengers?

A

cAMP, cGMP, Ca2+

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3
Q

What two things can activate a second messenger?

A

Enzymes and opening of ion channels

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4
Q

What does cAMP target?

A

Protein kinases

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5
Q

What are some examples of hormones that act through cAMP mediated mechanism?

A

ACTH (Adrenocorticotropic hormone)- cortisol expression
Glucagon (increase blood sugar)
TSH (Thyroid stimulating hormone)
Vasopressin (antidiuretic hormone, ADH)

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6
Q

What is generated from ATP by adenyl cyclase?

A

cAMP

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7
Q

What enzyme activate cAMP?

A

Adenyl cyclase

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8
Q

Describe the general pathway involving cAMP that results in target cell responses

A

Receptor activated by 1st messenger that binds> GTP is made and activates the alpha subunit of G-protein>activated G-protein activates adenyl cyclase>Adenyl cyclase converts ATP to form cAMP> cAMP targets protein kinase> protein kinase triggers responses of target cells.

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9
Q

What types of responses does cAMP elicit with glucagon, vasopressin/ADH, Parathyroid hormone, and catecholamine (epinephrine)?

A

-Mediates hormonal responses, such as mobilization of stored energy in the liver (glucagon)
-Conservation of water by kidneys via hormone vasopressin
Vasopressin = antidiuretic hormone (anti-urination)
-Calcium homeostasis via parathyroid hormone
Calcium deposition or liberation in the bone
-Increased heart rate and force of contraction via catecholamines: epinephrine (adrenaline), norepinephrine(noradrenaline), anddopamine – released by the nervous system/adrenal gland

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10
Q

Explain the pathway that occurs in the liver once epinephrine binds to the G-protein receptor.

A

Flight or fight response- release of epi from nervous system (need more glucose)> activates G protein (receptor that needs to be signaled)> causes adenylate cyclase to from cAMP from ATP> Which will then activate protein kinase> phosphorylates glycogen synthase (Activating it)> breakdown glycogen in the liver to form glucose> and it leaves the cell to fuel which ever tissue needs it.

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11
Q

T/F: Calcium is more widely used tham cAMP.

A

true

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12
Q

What is Ca2+ used for?

A

Used in neurotransmitters, growth factors, some hormones

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13
Q

Increases in Ca2+ causes many responses such as:

A

Muscle cell contraction
Secretion of certain substances
Cell division

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14
Q

What is the main function of IP3 ?

A

IP3s main function is to mobilize Ca2+ from storage thus resulting in Muscle cell contraction,
Secretion of certain substances,
Cell division

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15
Q

What is Phospholipase C ?

A

is a membrane bound enzyme that is activated by a G protein called Gq

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16
Q

What occurs when Phospholipase C is activated?

A

When active, phospholipase C breaks down a particular phospholipid called phosphatidylinositol 4,5-bisphosphate into two active signaling molecules : IP3 and DAG

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17
Q

What is IP3 and what does it do once it binds to IP3 receptors?

A

IP3 is small and water soluble, so it dissociates from the membrane and enters the cytosol where it can bind to IP3 receptors on smooth ER and cause a release of stored calcium

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18
Q

What does DAG do after its broken down by phospholipase C ?

A

DAG stays associated with the membrane, and activates protein kinase

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19
Q

Describe the pathway that occurs from the moment a 1st messenger binds to a G-protein and calcium is released by the endoplasmic reticulum.

A

Signal molecule binds with G protein, alpha sub-unit is activated by formation of GTP, which activates Phospholipase C, which ultimately forms IP3 and DAG. 1P3 bind to its receptors to open ca2+ release channel in the endoplasmic reticulum, causing release of Ca2+. DAG stays at the membrane and activates protein kinase.

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20
Q

What is angiotensin?

A

Angiotensin is a peptide hormone that causes vasoconstriction and a subsequent increase in blood pressure. It is part of the renin-angiotensin system, which is a major target for drugs that raises blood pressure. Angiotensin also stimulates the release of aldosterone, another hormone, from the adrenal cortex.

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21
Q

What effect does epi do when bound to beta adrenergic receptor?

A

produces cAMP> relaxation

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22
Q

Aceinhibitors prevents production of?

A

Angiotensin

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23
Q

Different doses of a drug can be tested in/on:

A

group of subjects, on isolated organs, tissues, or cells

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24
Q

Dose-Response Relationship is:

A

Relationship between drug concentration at receptor site AND magnitude of response; Relationship between amount of drug and some effect

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25
How is dose-response data important ?
mathematical relationships signify that a drug is working according to a specific interaction between different molecules in the body
26
When testing a potential drug, researchers must first show three things are true. What are they?
If the drug isn’t there, you don’t get any effect (no decrease in blood pressure) Adding more of drug (up to a certain point) causes an incremental change in effect (lower blood pressure with more drug) Taking drug away means there is a return to the original effect (blood pressure rises to the premedication level)
27
What is a dose response curve?
Relationship of dose to response can be illustrated as a graph
28
What kind of experiments can you show by changing the y-axis (plot response//effect) and maintaining the x-axis (concentration of drug)?
- Enzyme activity - Accumulation of an intracellular second messenger - Membrane potential - Secretion of a hormone - Heart rate or contraction of a muscle
29
ED50
ED50 – (Median Effective Dose) - dose at which 50 percent of the population or sample manifests a given effect
30
What two ways can the shape of curve be plotted?
Linear graph | Semi-logarithmic graph
31
How is the Semi-logarithmic scale better than a linear graph?
Range of doses may span several orders of magnitude By using the log of concentration, complete range of doses can be graphed Easier to estimate ED50
32
What are the 4 standard parameters?
-Baseline response (Bottom) -Maximum response (Top) -Slope -ED50 Half maximal effective concentration Located halfway between baseline and maximum Determines potency
33
What 2 terms can be used to describe a dose-response relationship?
``` Graded Response (Arithmetic) Describes effect of various doses of a drug on an individual ``` ``` Quantal Response (All-or-none) Describes effect of various doses of a drug on a population ```
34
Define Graded-dose response relationship.
As concentration of a drug increases, magnitude of its effect increases Relationship between dose and response is a continuous one Can be mathematically described assuming simplest model of drug binding Response is proportional to fraction of receptors occupied Max response occurs when all receptors are occupied Response is a graded effect Meaning response is continuous and gradual A graph of this relationship is known as Graded Dose–Response Curve
35
Graded-Dose Response Curve, illustrates relationship between?
Illustrates relationship between drug dose, receptor occupancy and magnitude of resulting physiologic effect. For a given drug Maximum response is produced when all functional receptors are occupied Half-max response is produced when 50% of functional receptors are occupied
36
Graded Dose-Response Curve helps to determine?
Potency Efficacy Helps to compare and choose among drugs
37
Potency
Potency refers to amount of drug (usually in milligrams) needed to produce an effect
38
A drug’s effects can be evaluated based on:
a drug’s strength (potency) and its efficacy (effectiveness)
39
Lower the ED 50 = (more or less?) potent the drug
MORE
40
T/F: ED50 is used to determine potency
TRUE
41
Efficacy
Ability of a drug to produce an effect
42
Do agonists-have positive efficacy?
Yes
43
T/F: Antagonists-have zero or no efficacy
TRUE
44
T/F: A drug with greater efficacy is less therapeutically beneficial than one that is more potent
FALSE
45
T/F: Quantal Dose-Response Relationship can cause both a therapeutic effect and toxic effect.
True
46
What are the 2 tpes of toxic effects?
TD50-median toxic dose | LD50-median lethal dose
47
What is Therapeutic Index (TI)?
The ratio of between dose causing undesirable effects (toxic/lethal) and the dose causing the desired therapeutic response TD50/LD50:ED50
48
What would a low TI help you determine?
Not a safe drug
49
What would a high TI help you determine?
Safe drug
50
TI for diazepam vs digoxin. Which one would be safer?
TI for diazepam = 100 (is somewhat forgiving) | TI for digoxin = 2 or 3 (not as forgiving)
51
Narrow Therapeutic Index (NTI)
Drug is typically considered to have a NTI when there is less than a two-fold difference in the median toxic/lethal dose and median effective dose
52
What must you do when a pt is on a drug with a Narrow Therapeutic Index (NTI)?
have its dosage adjusted according to measurements of the actual blood levels. This is called therapeutic drug monitoring
53
small dose range between what’s effective and what’s lethal
Narrow TI drugs
54
large dose range
Large TI drugs
55
Can both quantal and dose-response curve be graphed as linear or semi-logarithmic plot?
Yes
56
Both quantal and dose-response curve provide?
Provide critical information needed for making rational therapeutic decisions Provide potency and efficacy information
57
Can a patient respond differently to the same drug at different times during course of treatment?
yes-Variation in Drug Responsiveness
58
T/F: Individuals response to a drug may vary considerably
TRUE
59
3 Types of Response Variations
- Idiosyncratic Response - Tolerance/Tachyphylaxis Response - Hyper/hypo-Reactive Response
60
Idiosyncratic Response Variations
Rare, abnormal response to a drug Cannot be explained by known pharmacologic action of drug Not an allergic response Can not be reproduced with regularity (in other patients) May or may not be dose dependent Potentially an uncommon response to a drug because of a genetic predisposition
61
Hypo-reactive or Hyper-reactive Response Variations
Intensity of effect of a given dose of drug is diminished or increased in compared what is typically seen Diphenhydramine (Benadryl) Excitation or increased sleepiness Opioid pain medications Excessive sleepiness or respiratory depression CYP2D6 polymorphisms
62
Tolerance Response Variations
Diminished response to a dose of a drug with continued use Thus larger doses are needed to achieve same effect Opioids Benzodiazepines Stimulants (caffeine)
63
Tachyphylaxis Response Variations
When responsiveness rapidly diminishes after administration Can happen after first dose Increasing dose does not increase response Sometimes caused by depletion or reduction of neurotransmitter responsible for creating the drug's effect Common with: amphetamines, ephedrine, nicotine Example: nitroglycerin for chest pain
64
Four general mechanisms that may contribute to variation in drug responsiveness
-Alteration in drug concentration that reaches the receptor -Variation in endogenous (having an internal cause or origin.) ligand concentration -Alteration in number and function of receptors Changes in components of response downstream of the receptor
65
What are some causes that lead to alteration in drug concentration that Reaches the Receptor?
-Usually due to pharmacokinetic factors (body effect on drug):Absorption, distribution, metabolism, excretion. Up-regulation of hepatic enzymes and auto-induction of metabolism -Other factors: Age, gender, weight, disease states, genetic differences in drug metabolizing enzymes. Change in active transport of drug from cytoplasm. MDR genes (multidrug resistance) - are involved in transporting drug Up-regulation of MDR gene - coded transporter expression is how tumor cells develop resistance to anti-cancer drugs
66
What causes Variation in Endogenous Ligand Concentration?
Propranolol Beta adrenergic receptor blocker (beta-blocker) Slows heart rate when high levels of catecholamines (epinephrine) are present Given for stage fright May not do anything if you are not performing (no increased amount of circulating catecholamines)
67
What are some causes that lead to Alterations in Number or Function of Receptors?
- Sometimes the number of available receptors can increase or decrease -Can be caused by hormones Thyroid hormones have been known to increase number of Beta-receptors in heart muscles -Tachyphylaxis and tolerance can reduce the number of functioning receptors
68
When repeated drug administration results in a diminished effect, the phenomenon is called
tachyphylaxis
69
In tachyphylaxis are the receptors still present?
yes, but not responsive
70
Voltage-gated channels, require a finite time (rest period) following stimulation before they can be activated again. During this recovery phase they are said to be “refractory” or “unresponsive” This phenomenon is also known as
Desensitization
71
What are some causes that lead to Alterations in Number or Function of Receptors?
Rebound phenomenon Pt given beta blocker (propranolol - which slows heart rate and lowers BP) the body will increase number of receptors in critical cells and tissue maintain homeostasis When b blocker (propranolol) is abruptly withdrawn, now the pt has an increased number of available beta-receptors, which will produce an exaggerated response (increased BP and HR)
72
What are some changes in components that may alter the response distal to a receptor?
Although a drug may bind to its intended receptor successfully, other processes can reduce the effects of a drug Example Administer Beta-blocker to lower blood pressure Beta-blockers work in the heart to lower BP If pt’s BP is not being lowered by Beta-blocker, it could be because kidneys are now holding on to water as a compensatory mechanism to raise BP The body generally tries to maintain homeostasis
73
What is clinical selectivity?
Drugs can be relatively specific to certain receptors Even though they are intended to be attracted to certain receptors, other intended effects and receptor binding can occur Dose dependent Higher selectivity is considered useful in clinical medicine Example Pesticides
74
How can selectivity be measured?
by comparing binding affinities of a drug to different receptors by comparing ED50s for different effects of a drug
75
In drug development selectivity, what two type of factors is considered?
Therapeutic effects vs. Toxic/side effects
76
Beneficial and Toxic Effects Mediated by SAME Receptor - Effector Mechanism
This is the case when the intended effect of the drug also causes toxicity because of its direct intended effect Example Warfarin (Coumadin) - intended effect is thinning blood Pt could have too much blood thinning leading to toxicity (GI bleed, stroke) Insulin - intended effect is lowering glucose Too much lowering can induce hypoglycemia Must weigh benefit vs. risk
77
Beneficial and Toxic Effects Mediated by Identical Receptors but in DIFFERENT tissues or by DIFFERENT Effector Pathways
Certain drugs which are used to treat an issue in one area of the body Glucocorticosteroids for asthma/COPD exacerbation (e.g., prednisone) Can cause toxicities in other areas because they bind to receptors elsewhere Increase glucose  diabetes, fluid retention Goal: Use lowest most effective dose Use more direct routes (inhalers) Use drugs with alternative mechanisms of action
78
Beneficial and Toxic Effects Mediated by Different Types of Receptors
By making drugs more selective to one receptor you can eliminate unintended effects and keep intended ones Drug discovery is often a result from a ligand that binds to several different receptors Example: EPI (epinephrine), bi
79
Beneficial and Toxic Effects Mediated by Identical Receptors but in DIFFERENT tissues or by DIFFERENT Effector Pathways
Certain drugs which are used to treat an issue in one area of the body Glucocorticosteroids for asthma/COPD exacerbation (e.g., prednisone) Can cause toxicities in other areas because they bind to receptors elsewhere Increase glucose  diabetes, fluid retention Goal: Use lowest most effective dose Use more direct routes (inhalers) Use drugs with alternative mechanisms of action Sometimes, side effects of medications lead to development of others Minoxidil (Rogaine) Originally a blood pressure lowering medication Found to cause increased hair growth
80
Clinical Selectivity
When selecting an agent for a particular patient, you have to consider factors such as side effects, potential toxicity, duration of effect Potency or efficacy does not always mean that one drug is better for a particular patient

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