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VM722 Pharm > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

Important characteristics of receptors

A
  • bind due to high affinity, so low amount of drug is required to cause an effect and the effect will take longer to end
  • effect depends on the drug that binds to the receptor
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2
Q

Law of mass action as it pertains to drug binding

A

Doesn’t matter how much is given, drug effect is proportional to how much drug bind to receptors (Kd)

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3
Q

Kd

A
  • Dissociation constant ([D][R])
  • Kd is the drug concentration needed to bind 50% of receptors
  • Measures affinity/potency of a drug
  • Fraction of the receptor bound (bound receptors/ total receptors)
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4
Q

EC__

A

Effective concentration to see ___% of max effect

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5
Q

Which is more potent? Smaller or bigger Kd?

A

Smaller - will bind to receptor longer, thus act for longer time

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6
Q

Potency

A

Compares drug concentrations needed to get 50% of max effect (EC50)

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7
Q

Efficacy

A

Measures maximal effect (because not all drugs achieve max activation of receptors)

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8
Q

Full agonist

A

Causes max activation of receptors at a high dose

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9
Q

Partial agonist

A

Does not achieve max activation of receptors at a high dose (less efficacious drug)

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10
Q

Which is more important: Efficacy or potency?

A

Efficacy

Less potent drug with high efficacy = better results than high potency, less efficacious drug

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11
Q

Buprenorphine vs. Morphine

A

B - potent, partial agnoist with high affinity binding (so smaller dose will cause moderate analgesic effect, but it lasts longer) (if follow with morphine, B won’t dissociate, so likely will just have moderate pain relief)

M - less potent full agonist with lower affinity binding (so doesn’t last as long, but stronger analgesic effect)

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12
Q

Agonist

A

Has an effect on the receptor

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13
Q

Antagonist

A

Binds to receptor but doesn’t have an effect, blocks effect of agonist
Alone, doesn’t cause a dose response curve/effect, just flat horizontal line

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14
Q

What if an agonist and a competitive antagonist are both given?

A

Dose response curve shifts to right

Greater dose of agonist required to get same effect

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15
Q

What if an agonist and a non-competitive antagonist are both given?

A

Dose response curve is shorter/pushed down (decreased max effect) - agonist is made less efficacious (still binds but antagonist still stops receptor from responding)

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16
Q

Classes of signal transduction pathways

A

Ionotropic (ion channels, fast)
Metabotropic (G-prot)
Transcription Factors (change gene expression)
Enzyme-linked

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17
Q

Name 3 situations where drug binding to receptor isn’t proportional to drug effect

A
  1. 2nd messenger cascades
  2. Spare receptors
  3. Tolerance/desensitization
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18
Q

Spare receptors

A

Max response occurs even when agonist doesn’t fully occupy all available receptors (e.g. NMJ)
-alters dose response curve

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19
Q

Tolerance/desensitization

A
  • previous/repeated exposure to drug may increases tolerance, decreasing drug effect
  • partly due to a decrease in number of receptors
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20
Q

Partial agonist

A

Less efficacious, induce partial (non-max) activation when bind to receptor

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21
Q

Naloxone

A
  • potent, partial opioid antagonist
  • reversal for morphine or buprenorphine
  • will reverse morphine faster than buprenorphine
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22
Q

Complex model of receptor binding

A
  • some receptors shift between active/inactive without binding of drug to stimulate shift
  • Assume some receptors are active without having bound drug
  • drug binding will “stabilize” receptors by causing them to remain in active or inactive state
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23
Q

Inverse agonist

A
  • binds to same receptor as agonist, but stabilizes it as inactive
  • reduces effect opposite that of the agonist
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24
Q

How do spare receptors affect ED/C50

A
  • EC50 will be lower than Kd

- with more spare receptors, a lower concentration will cause effect

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25
Q

Quantal/Population cumulative distribution curve

A
  • not a true dose response curve
  • curve made based on frequency distributions seen in a population
  • measures if animal responded to drug or didn’t at each point
  • NO predictive value to graph
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26
Q

use of population curves for toxicity studies

A

Used to estimate drug safety by determining therapeutic index

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27
Q

Therapeutic index

A

LD50/ED50 = TI

Compares dose/concentration that causes effect with dose/concentration that causes toxic effect

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28
Q

What therapeutic index number is considered safe?

A

> 10

larger TI = safer drug

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29
Q

Standard safety margin

A

% by which the ED99 must be increased before an LD1 is reached

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30
Q

Therapeutic window

A

Window where many patients get a good response and only a few toxic effects occur

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31
Q

Tachyphylaxis

A

acute drug desensitization

occurs after initial dose or after series of small doses

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32
Q

Down regulation

A

A decrease in the number of receptors responding to a drug, making cells less sensitive to the drug

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33
Q

What determines drug concentration?

A

drug (g) / volume (l)

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34
Q

Central compartment organs

A
  • brain, spinal cord, retina

- well perfused, drug has rapid effects

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35
Q

Peripheral compartment organs

A
  • skin, muscle, fat

- not well perfused, drug has slower effects

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36
Q

Advantages of parenteral drug administration (vs. oral)

A

-avoids lack of uptake issues with GI
-avoids elimination by the liver
aka you know it’s in there
-rate of uptake into blood usually faster

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37
Q

Advantages of oral drug administration (vs. parenteral)

A

-rate of uptake into blood usually slower

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38
Q

IV administration

A
  • absorption circumvented
  • fast
  • provides bolus
  • constant rate of infusion leading to steady state
  • can give irritating solutions (b/c rapid dilution) or large volumes
  • don’t give oils or suspensions
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39
Q

Bolus

A

Initial spike of drug into blood
Drug in central compartment first, then rapidly moves to peripheral
Once in peripheral compartment, slow decrease b/c removed only by elimination

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40
Q

steady state

A
  • constant level of drug in the blood

- Only at this state does animal get full benefit of the drug.

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41
Q

Subcu administration

A
  • aqueous solutions absorbed promptly
  • repository, slow sustained release
  • don’t give large vol, irritants
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42
Q

IM administration

A
  • aqueous solutions absorbed promptly
  • repository, slow sustained release
  • can give moderate volumes, some oils, some irritants
43
Q

IP (peritoneal)

A
  • mostly useful for lab animals
  • FAST
  • don’t give irritants
44
Q

Pulmonary administration

A
  • must be non-irritating aqueous drugs given in gas form
45
Q

Bioavailability (F)

A
  • fraction of oral drug that is absorbed, escapes first pass elimination and makes it into systemic blood
  • F = Area under curve oral / AUC iv
46
Q

Oral administration

A
  • bioavailability variable (GI blood –> liver –> elimination)
  • usually slower onset
  • typically more economical, safe, convenient
  • not usually used for Rum
  • multiple doses required to reach a steady state
47
Q

Drug absorption from gut depends on

A

drug form and solubility

48
Q

Who moves better across membranes:
lipid soluble vs. polar
small vs. large

A

lipid soluble > polar (uncharged vs. charged)

small > large (polar water can cross b/c small)

49
Q

What drug type is best absorbed in stomach

A

acidic environment so lipid soluble drugs and weak acids (uncharged) best absorbed

50
Q

What drug type is best absorbed in SI?

A

basic envornment so weak bases best absorbed

51
Q

First pass effect

A
  • Drugs given orally primarily absorbed in stomach, GI

- Portal circulations from these organs go to liver where drugs are metabolized or secreted into bile

52
Q

Vd (volume of distribution)

A
  • If you know this, you can determine what the drug concentration will be in the blood
    or amount of drug in the body
  • very variable depending on drug characteristics (solubility, is it protein bound, CNS penetration etc)
  • greater Vd = more likely to redistribute into other compartments
53
Q

What can penetrate BBB?

A

non-polar drugs

54
Q

What drug types deposit in fat? bone?

A

fat - lipid-soluble drugs

bone - tetracyclines

55
Q

What happens when drug binds to plasma protein?

A
  • albumin & plasma proteins bind drugs with low affinity
  • only free drug can bind receptors
  • plasma concentration of drug doesn’t = concentration of actively working drug
56
Q

How can liver disease affect free drug circulation?

A

Liver has decreased protein production –> less bound drug, more free drug in circulation

57
Q

Phase 1 reaction

A
  • in liver
  • Cytochrome P450 oxidizes/hydrolyzes/reduces drug (typically inactivating them)
  • usually makes it more water soluble for easier excretion
58
Q

2 main routes of drug elimination

A

Metabolized in liver

Excretion by kidney

59
Q

P450’s

A
  • Nonspecific
  • Can be induced by other drugs to increase rate of drug elimination
  • things like grapefruit juice can inhibit their function
60
Q

Phase 2 reaction

A
  • Conjugation of drugs in the liver

- makes them more water soluble for easier excretion in kidney

61
Q

How does filtration move drugs from blood to urine

A
  • at level of glomerulus
  • small molecules –> urine
  • only drug bound to plasma protein (albumin) isn’t filtered
62
Q

How does secretion move drugs from blood to urine

A
  • at the level of proximal convoluted tubules
  • cells of pct’s secrete organic acids or bases drugs into urine via transporters
  • if pH of urine causes these drugs to uncharged form, some may be reabsorbed back into blood by diffusion
63
Q

How does the liver eliminate drugs?

A
  • put into biliary system via transporters
64
Q

3 measures of elimination

A

Clearance
Half Life
Rate constant of elimination

65
Q

Clearance

A

-vol of drug cleared by an organ per unit time (CL = Clrenal + CLliver + CLother)

66
Q

If clearance is decreased 50%, what does that do to drug half life?

A

doubled

67
Q

Half-life

A
  • Time to reduce drug concentration to half the original concentration
  • decreased clearance = longer half life
68
Q

Rate of constant elimination

A

Kel = 0.693/half life time

Inversely proportional to half life

69
Q

1st order kinetics

A
  • Drugs normally eliminated by 1st order

- the more drug you have the faster it is eliminated

70
Q

zero order kinetics

A
  • Few drugs eliminated by zero order

- same amount eliminated per hour regardless of concentration (e.g. alcohol)

71
Q

Bolus vs. infusion

A

Bolus - drug all at once, bit of redistribution, plasma level depends on clearance

Infusion - slow, plasma levels low then approach steady state

72
Q

steady state

A

after drug reaches equilibrium of uptake vs. elimination, it maintains a steady state of plasma concentration (assuming dose kept same)
reached in ~4 half lives (time NOT dose dependent)

73
Q

continuous infusion vs. repeated doses and steady state

A

Both reach steady state in ~4 half lives

Repeated doses acts same, just with fluctuations

74
Q

Steady state levels are proportional to ___ and inversely proportional to ____

A
  1. dosage (doubled dosage = doubled level of steady state) or bioavailability
  2. dose interval (e.g. q 4 hrs) or clearance
75
Q

Fluctuations to steady state level are proportional to ___ and inversely proportional to ___

A
  1. dose interval (short interval = small flux)

2. half life

76
Q

Blood levels of a drug are ~1/2 what you want. How can you increase the average blood level to twice the original level/

A

double the dose or cut the dose interval to .5

77
Q

How can you reduce the fluctuations without changing average drug concentrations?

A

Cut the dose interval of the drug to ½, and also reduce the dose to ½ to keep the average concentration the same.

78
Q

The clearance is estimated to be ½ of normal. What changes could you make in the recommended dose to get the optimum blood level?

A

With decreased clearance, the blood levels would approach twice normal.
You could cut the dose to ½ or double the dose interval.

79
Q

Giving a concentration-dependent antibiotic (want brief periods of high drug levels)

A

higher doses with longer dose interval

80
Q

Giving a time-dependent antibiotic (longer periods of use at minimal levels)

A

lower dose with shorter dose interval

81
Q

Loading dose

A

Shortens the time to get to steady state concentration

82
Q

What adds variability to drug effect?

A

blood concentration

effect through receptor

83
Q

Pharmacokinetics

A

variability in blood concentration

84
Q

3 factors that contribute to 9-fold range in blood concentration of drug

A

Clearance - kidney function, GFR, RAA system varies
Vol of distribution - different percent of fluids, bone, muscle in different animals
Bioavailability - blood levels vary

85
Q

pharmacodynamics

A

variations in effect at a fixed concentration

changes in receptors/activation may increase variability

86
Q

What molecule types can cross membranes without a transporter?

A 
hydrophobic molecs (uncharged acid/base forms)
small molecules (NO, H2O)
87
Q

P glycoprotein

A
  • ATP binding casette transporter
  • saturable
  • removes ivermectin from the brain, may also transport digoxin, etc.
  • “white feet don’t treat” - collies etc. with decreased production of p glycoprotein & ivemectin toxicity
88
Q

Type I hypersensitivity

A

allergy –> atopy –> anaphylaxis

89
Q

Atopy

A

allergen is having an effect somewhere else in the body that where the reaction is happening

90
Q

2 methods for causing toxic drug reaction

A
  1. too high of dose activates too many receptors or activates wrong low-affinity receptors
  2. non-receptor mediated - nasty compounds formed during metabolism in liver (e.g. acetaminophen) that hurt the liver
91
Q

How can a 2nd drug interfere and cause adverse reaction?

A
  • if animal has increased or decreased/inhibited cytochrome P450
  • inhibition of p glycoprotein transporter (= drug accumulation)
  • can displace original drug bound to proteins- bad or gets eliminated
92
Q

Pharmacology (vs. toxicology)

A
  • Compound given intentionally, not damaging
  • study of potions
  • receptor mediated effects that end when compound gone
93
Q

Toxicology (vs. pharmacology)

A
  • compound not given intentionally, damaging
  • study of poisons
  • receptor and non-receptor mediated effects, with changes/damage persisting after toxin is gone
94
Q

receptor mediated toxicity

A
  • drug binds to important receptors/enz, disrupt activity –> damage, death
  • +/- excitotoxicity
  • or low affinity binding to abnormal receptors when drug is in excess
  • e.g. HAB’s, insulin toxicity in cats - seizures
95
Q

excitotoxicity

A

overstimulation of normal receptors = disruption

-e.g. glutamate excess kills neurons

96
Q

non-receptor mediated toxicity

A
  • not very selective, potent
  • much larger amounts required
  • toxic metabolites formed
  • e.g. ethylene glycol, acetaminophen
97
Q

Why should you give drugs based on surface area?

A

Metabolic rate changes more similarly to SA (vs. weight)

98
Q

Exotherms and drugs

A
  • lower metabolic rate

- drug half life depends body temp

99
Q

In what animals is drug half life the shortest? longest?

A
  1. rum, EQ

2. cats

100
Q

What do cats have poor conjugation of?

A

Glucuronic acid - half life of aspirin extended

101
Q

what drug types does the rumen trap?

A

hydrophobic bases (e.g. ivermectin)

102
Q

Charged vs. uncharged groups and urine excretion

A

charged - better excreted in urine

uncharged - can be resorbed back into body

103
Q

How much liver damage is required to overwhelm metabolism of drugs?

A

> 80%

104
Q

what animals are tricaine methanesulfonate (MS-222) approved for use in?

A

Fish (or clove oil)

Amphibians (or Iso)

VM722 Pharm (5 decks)

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