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Pharmacology > module 7-11 > Flashcards

module 7-11 Flashcards

1
Q

what is pharmacodynamics?

A

study of what the drug does to the body

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2
Q

what are the phases of the dose-response curve and what does each phase mean?

A

Phase I - doses too low to elicit clinically relevant response
Phase II- response is graded and nearly linear
Phase III- larger doses do not lead to greater response, larger doses may cause toxicity

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3
Q

what is efficacy a measure of?

A

how effective a drug is at a given dose

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4
Q

what is maximal efficacy?

A

maximum effect drug is capable of achieving

is the max height on a dose response curve

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5
Q

what is potency?

A

amount of drug required to elicit a pharmacological response

*a more potent drug will require a smaller dose to achieve the desired effect than a less potent drug

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6
Q

what is ED50?

A

dose required to produce the half maximal response

  • literally means effective does in 50% of the pop’n
  • low ED50 more potent than high ED50
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7
Q

what are all the targets of drugs?

A

receptors, enzymes, ion channels, transport proteins

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8
Q

what is an example of a drug that has no cellular targets?

A

antacids - they simply neutralize stomach acid

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9
Q

what are 4 types of drug receptors?

A

ligand-gated ion channels
g-protein coupled receptors
enzyme linked receptors
intracellular receptors a.k.a. transcription factors

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10
Q

what is an example of a ligand gated ion channel?

A

GABA receptor opens chloride receptors (flow into cell)
benzodiazepines bind to these
causes sedation and muscle relaxation, very rapid response

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11
Q

describe the action of g-protein coupled receptors (GPCRs)

A

binding of ligand, g-protein dissociates from receptor and activates the effector
response is seconds to minutes in duration

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12
Q

what are endogenous examples that bind to GPCRs?

A

neurotransmitters - norepinephrine, serotonin, histamine

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13
Q

describe action of enxyme linked receptors

A

ex. insulin
insulin binds to receptor which releases a phosphate on inside of cell, the phosphate binds to the effector which causes the glucose transporter to move to the cell surface

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14
Q

explain intracellular receptors

A

receptor is on inside of cell
ligand must enter cell and bind to the receptor, then this complex moves into the nucleus and binds to DNA
-effects protein synthesis

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15
Q

explain the simple occupancy theory

A

1) the intensity of a drug’s response is proportional to the number of receptors occupied
2) the maximal response occurs when all receptors are occupied

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16
Q

what is the modified occupancy theory?

A

1) the intensity of a drug’s response is proportional to the number of receptors occupied
2) two drugs occupying the same receptor can have different binding strengths (affinity)
3) two drugs occupying the same receptor can have different abilities too activate the receptor (intrinsic activity)

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17
Q

what is affinity a primary determinant of?

A

a drug’s potency

high affinity = high potency

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18
Q

what is intrinsic activity a reflection of?

A

its efficacy

high intrinsic activity = high maximal efficacy

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19
Q

what does agonist mean?

A

a molecule that binds to a receptor and activates it

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20
Q

what does antagonist mean?

A

a molecule that binds to a receptor but does not activate it

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21
Q

what is a partial agonist?

A

molecules that binds to a receptor but have minimal ability to activate it

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22
Q

what are examples of atnagonists?

A

beta blockers - block binding of epinephrine, slows heart rate
antihistamines - block binding of histamine, prevents symptoms of allergy
gastric acid reducers - block binding of histamine, decrease gastric acid secretion
opioid receptor blockers - block binding of opioids, treat opioid overdose

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23
Q

what are the 3 types of antagonists?

A

competitive - bind to same site as agonist, reversible
irreversible- bind to same site as agonist but irreversible
allosteric - bind at diff site than agonist

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24
Q

what is drug tolerance?

A

when patients continually exposed to agonists, the response of the agonist may decrease

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25
Q

what are the types of drug tolerance?

A

desensitization - repeated exposure =receptor internalized in cell or destroyed, less sruface receptors therefore decreased drug effects
metabolic tolerance - continuous exposure results in induction of drug metabolizing enzymes = decrease in plasma conc. of drug
tachyphylaxis - rapid decrease in response to drug. Some drugs require a drug free peroid between admins to prevent this eg. transdermal patches

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26
Q

what is receptor upregulation?

A

continuous exposure to an antagonist results in cell to become hypersensitive
cell synthesizes more receptors

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27
Q

what are all the phases of drug trials?

A

Phase 1 - 20-100 volunteers, animal studies guide dosing
Phase 2- 300-500, efficacy & short-term effects, dose-response dtermined
Phase 3 - 500-5000, efficacy verifies and long-term side effects eval
Phase 4 - post-marketing surveillence

28
Q

how is the ED50 determined?

A

during phase 2 eval the number of patients experience drug effect (eg. pain relief) from each dose of the drug

  • the avg effective dose (ED50) is at the peak of the freq distrib curve
  • ED50 is the dose required to produce a response in 50% of the pop’n
  • ED50 often used as initial dose for therapy
29
Q

when is it ok to use the ED50 as the starting dose?

A

wide therapeutic range

*narrow therapeutic range should have dose titrated - start low and increase slowly

30
Q

what is the TD50?

A

a.k.a. avg toxic dose, the dose in which 50% of animals experience drug toxicity

31
Q

what is LD50?

A

a.k.a. avg lethal dose, dose in which 50% of animals die

32
Q

how are the TD50 and LD50 expressed?

A

mg drug/kg body weight

33
Q

what is the therapeutic index?

A

indicator of drug safety

34
Q

what is an example of when race needs to be accounted for in dosing?

A

concentrations of the cholesterol lowering drug rosuvastatin are 2-3 times higher in asian compared to caucasian patients therefore lower dose required in asian patients

35
Q

what needs to be considered when clt has kidney disease?

A

drug excretion decreased
increase in half-life
if renal failure, hepatic & intestinal drug metab decreased & there is increase oral bioavailability and dec excretion
need lower dose for ppl with kidney disease

36
Q

what needs to be considered when clt has liver disease?

A

decreased drug metabolism

for drugs that are extensively metabolized, half life may be significantly increased

37
Q

what are examples of environmental exposures that change response to drugs?

A
  1. cigarette smoke induces drug metabolizing enzymes and make drugs less effective
  2. alcohol can exacerbate toxicity
  3. exercise improves action of insulin
  4. some pesticides induce CYPs and therefore decrease the response to drugs that are metabolized by CYP enzymes
38
Q

what is the main point about drug toxicity?

A

often extensions of the therapeutic effect

39
Q

what most commonly causes drug allergic reactions?

A

penicillin

and also sulfonamides and NSAIDs

40
Q

what is measured in a liver function test?

A

aspartate aminotransferase (AST) & alanine aminotransferase (ALT)
these are enzymes that are uauslly at low levels
increase levels indicates liver damage

41
Q

what is the QT interval?

A

represents the time required for the ventricles to repolarize
A prolongation of the QT interval is a major risk factor for the development of torsades de pointes - ventricular arrhythmia

*women at higher risk because normal QT interval is longer

42
Q

what are examples of drugs that will cause withdrawal symptoms?

A

opiates - anorexia, irritability, nausea, vomiting, weakness, muscle-spasm
benzodiazepines - anxiety, insomnia, sweating, tremours, panic, delirium, paranoia, convulsions
beta blockers - rebound hypertension, chest pain, myocardial infarction, arrhythmia

43
Q

what are three possibel outcomes of drug interactions?

A

increased effects
decreased effects
generation of a new effect

44
Q

what are two examples of increased affects?

A

you can have either an increased therapeutic effect or increased adverse effect

  • ampicillin is rapidly inactivated by bacterial enzymes, sulbactam inhibits the enzyme so put them together and increased therapeutic effect of ampicillin
  • warafrin thins blood and aspiriin thins blood = together, too much bleeding (increased adverse effect)
45
Q

what is an example of a decreased adverse effect?

A

morphine overdose

naloxone is administered (competitive antagonist)

46
Q

what is the most common type of drug interaction?

A

pharmacokinetic interaction

47
Q

what are all the types of drug interaction?

A

direct physical, pharmacokinetic, pharmacodynamic, combined toxicity

48
Q

describe direct physical interactions

A

usually when 2 or more IV solutions mixed, can cause precipitate to form (do not use if this happens)
diazepam should never be mixed with another drug

*sometimes can form precipitate in blood after admin eg. sodium bicarb followed by calcium gluconate

**need to use compatibility chart when mixing meds

49
Q

describe the pharmacokinetic interaction when pH is altered during (absorption)

A

drugs that affect gastric or intestinal pH

eg. antacids - increase gastric pH therefore increase absorption of weak base and decrease absorption of weak acids
* also dramatically affect absoprtion of enteric coated drugs (premature dissolution - can have toxic effects on the stomach or the drug may be destroyed in the acid of the stomach)

50
Q

describe example of chelation/binding

A

drugs binding together in the intestine

bile acid sequestrants eg. cholestyramine binds to digoxin - decreases absorption

51
Q

altered blood flow absorption

A

use of epinephrine with local anesthetic

epinephrine causes vasoconstriction and decreases absorption keeping the anesthetic at the local site

52
Q

gut motility

A

any drug increasing motility decreases absorption because there is less contact with microvilli
laxatives increase motility
opiates decrease motility and increase absorption

53
Q

vomiting

A

if vomiting occurs 20-30 minutes after taking 1 or more meds it is likely that absorption incomplete
tough choice to administer more meds or not because either the pt didn’t get proper dose or at risk for toxicity

54
Q

drugs that kill intestinal bacteria

A

eg. oral contraceptives rely on intestinal bacteria to deconjugate metabolites so the parent drug can be recycled and absorbed back into circulation
antibiotics kills bacteria so there would be less/no bacteria to deconjugate thus decreasing plasma concentration of the oral contraceptive
-could lead to unwanted pregnancy

55
Q

altering pH distribution

A

sodium bicarbonate increase extracellular pH whereas ammonium chloride decreases extracellular pH
changing extracellular pH can draw a drug from inside to outside the cell
eg. overdose aspirin, sodium bicarb increase extracellular pH and draws out the aspirin and becomes trapped and more easily excreted through urine

56
Q

protein binding

A

if two drugs bind to the same site on plasma proteins, co-admin will result in competition binding
-may result in increased therapeutic effect, increased toxicity and/or increased excretion

57
Q

CYP induction

A

some drugs increase synthesis of CYP enzymes a.k.a. induction - result is increased metabolism
induction is delayed - 2-10 days following exposure to inducer before induction occurs

58
Q

CYP inhibition

A

results in decreased metabolism
typically results in increased plasma concentration of parent drug
if pro-drug given when CYPs are inhibited, there will be decreased metabolic activation

59
Q

what are examples of CYP inhibitors?

A

antibiotics and antifungals CYP3A4
SSRIs inhibit CYP2S6
grapefruit juice CYP3A4

60
Q

altered blood flow excretion

A

drugs that decrease renal blood flow, decrease glomerular filtration, decrease renal excretion and therefore higher plasma drug concentrations

61
Q

what are two examples of drugs that decrease renal blood flow?

A

beta blockers - decrease CO which indirectly decreaes renal blood flow

62
Q

altered pH excretion

A

distal tubule
if pt. overdoses on amphetamine ( weak base) the filtrate can be acidified with ammonium chloride which ionizes the drug and prevents reabsorption d/t pH partitioning

63
Q

tubular secretion

A

transporters in proximal tubule
one drug blocks transporter so other drug stays in blood and is not excreted
eg.penicillin and probenecid (used to treat gout)
-probencid blocks transporter, keeps penicilllin in blood

64
Q

2 types of pharmacodynamic interactions

A
  1. interactions that occur at same receptor

2. interactions that occur at separate sites

65
Q

explain interactions that occur at diff sites

A

two drugs that have completely different mechanisms can produce a drug interaction if they produce same physiological effect
morphine and diazepam are both CNS depressants
if both taken together = enhanced CNS depression

66
Q

what is combined toxicity?

A

2 drugs that cause for example hepatotoxicity
acetaminophen and alcohol

example - TB drugs isoniazid and rifampin are both hepatotoxic but are required to be used together so liver function tests must need to be taken

67
Q

examples of food-drug interactions

A 
monoamine oxidase (MAO) must avoid foods containing tyramine (aged cheese, yeast, sauerkraut, cured meat, soy sauce) because MAO inhibitors inhibit the breakdown of tyramine and excess tyramine cauuse release of norepinehprine resulting in hypertensive crisis
*symptoms include tachycardia, severe hypertension, headache, nausea & vomiting

Pharmacology (7 decks)

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