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Pharmacology > Quiz 1- Pharmocokinetics, Pharmocodynamics > Flashcards

Quiz 1- Pharmocokinetics, Pharmocodynamics Flashcards

1
Q

What is pharmacokinetics all about?

A
  • Absorption
  • Distribution
  • Metabolism
  • Excretion
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2
Q

What is bioavailability?

A

The percent of medication that reaches systemic circulation.

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3
Q

What affects the bioavailability?

A

ABSORPTION

  • Dissolution and absorption characteristics
  • Route
  • Stability in GI tract
  • Metabolism prior to blood stream

Example: Redosing synthroid IV to PO because bioavailibility of IV= 100%
need to increase dose

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4
Q

What consideration should be made about oral administration?

A
  • Gastric pH and contents
  • Surface area
  • Blood flow
  • GI Motility
  • Complete GI tract
  • Flora
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5
Q

What considerations should be made about sublingual/buccal administration of drugs?

A
  • Drains to vena cava (no 1st pass)
  • Very rapid
  • Must be HIGHLY lipid soluble and potent
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6
Q

What happens to drugs taken orally?

A

1st Pass Metabolism:
-90% percent of oral medication is metabolized and destroyed by the liver before it gets to the heart

some meds wouldn’t make it past this

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7
Q

Topical administration into the eye should have special consideration because?

A

The medication could become systemic due to the nasolacrimal canal

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8
Q

What should be consider for inhalation of drugs?

A
  • Rapid due to large surface area
  • Avoid first pass-Local site of action
  • Difficult to control
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9
Q

What is volume of distribution?

A

Size of compartment necessary to account for the total amount of drug in the boy if it were present throughout the body at the same concentration found in the plasma.

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10
Q

What is the volume of distribution in an average adult’s plasma?

A

3 Liters

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11
Q

What is the volume of distribution for total body water?

A

0.65 L/kg

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12
Q

What is the formula for loading dose?

A

Volume of distribution x Desired concentration = Loading dose

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13
Q

What is involved in two compartment model?

A
  • redistribution before elimination
  • Slow rate of administration for secondary redistribution
  • Target organ may be in the initial or secondary “compartment”
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14
Q

What should be known about protein binding drugs?

A
  • Unbound/free drug = active
  • acidic drugs: albumin
  • Basic drugs: alpha 1 acidic glycoprotein
  • Generally reversible
  • Saturable
  • Non-linear
  • Competitive
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15
Q

What should be known about tissue binding?

A
  • Fat: Reservoir for lipid soluble drugs
  • Bone: Tetracyclines
  • Heart muscle: Digoxin
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16
Q

What is membrane permeability?

A

Drugs ability to permeate all membranes that separate the organ from the site of drug administration.

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17
Q

Are benzodiazepines membrane permeable and how does it work?

A

The are very lipophilic and cross the gut wall, capillary wall and blood brain barrier. Great for treating anxiety and seizures.

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18
Q

What are the point for placental transfer?

A
  • fetal plasma is more acidic:ion trapping of basic drugs occurs
  • P-glycoproteins limit transport in
  • Fetus is exposed to nearly all medication a mother takes
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19
Q

What are P-glycoproteins?

A
  • Family of transporter proteins
  • Found all over, including the blood brain barrier (kidney, colon, jejunum, liver, pancreas)
  • Important for medication interactions and drug resistance
  • Requires ATP
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20
Q

What are the mechanisms for drug transport across membranes?

A
  • Passive diffusion
  • Facilitated diffusion
  • Aqueous channels
  • Active transport
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21
Q

Does passive diffusion require energy and a carrier?

A

Energy: No
Carrier: No
Note: Rapid for lipophilic, nonionic, small molecules

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22
Q

Does facilitated diffusion require energy and a carrier?

A

Energy: No
Carrier: Yes
Notes: Drugs bind to carrier by noncovalent mechs. Chemically similar drugs compete for channel.

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23
Q

Does aqueous channels require energy and a carrier?

A

Energy: No
Carrier: No
Notes: Small, hydrophilic drugs diffuse along concentration gradient by passing thru aqueous channels/pores.

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24
Q

Does active transport require energy and a carrier?

A

Energy: Yes
Carrier: Yes
Notes: Identical to facilitated diffusion except that ATP powers drug transport against concentration gradient.

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25
Q

What occurs during phase 1 metabolism?

A
  • induce or expose a functional group on the parent compound (by oxidation, reduction, hydrolysis)
  • Then often hydrolyzed or ester linked for rapid elimination thru the kidneys
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26
Q

What occurs during phase 2 metabolism?

A
  • Conjugation reactions

- Links parent compound OR phase 1 metabolite with a functional group via covalent linkage

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27
Q

MOST reactions are ______ driven

A

Enzyme

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28
Q

What is inhibition?

A

Will keep the enzyme from working properly.

Inhibitors have the potential to interact with each other

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29
Q

What is induction?

A

Will enhance the capability of the enzyme.

30
Q

What is Cytochrome P450?

A
  • Terminal oxidase in a multicomponent electron transfer chain (mixed fx oxidase system).
  • Is the largest family of enzymes responsible for breaking down 75% drugs
31
Q

What factors affect metabolism of a drug?

A
  • genetics
  • environmental (diet)
  • Disease factors (liver, kidney)
  • Age: peds/geriatrics
32
Q

What are the routes of elimination?

A
  • Renal #1
  • Biliary
  • Fecal
  • Sweat
  • Saliva
  • Tears
  • Lungs
33
Q

What is the equation for Ideal Body weight of a male?

A

IBW = 50 + (2.3 x inches > 5 feet)

34
Q

What is the equation for ideal body weight of a female?

A

IBW = 45.5 + (2.3 x inches > 5 feet)

35
Q

What are the modifications needed for the creatinine clearance equation?
(formula will be provided on test)

A

CrCl = (IBW) x (140 - age) x 0.85 (female)
————————
Cr x 72
-* if patient >65, round Cr up to 1 if <
- *use the LOWER body weight (of IBW vs ABW- actual body weight)

36
Q

How many doses does it take to achieve a steady state??

A

5 half lives
- because we can’t change the rate out, only the rate in (so loading dose/ increased frequency wont help to reach SS faster)

37
Q

Why do you check a trough level?

A

Checking efficacy

38
Q

Why do you check a peak?

A

Checking for toxicity

39
Q

What are the GENERAL receptors found on a cell?

A

Proteins or glycoproteins

40
Q

What happens after receptor saturation occurs?

A

Receptor mediated responses plateau

41
Q

What happens after a drug is bound to a receptor?

3 common actions:

A
  • An ion channel is opened or closed
  • Biochemical messengers (second messengers) are activated.
    - Biochemical messengers initiate a series of chemical reactions within the cell, and transduce the signal stimulated by the drug
  • A normal cellular function is physically inhibited or initiated.
42
Q

?What are the three points to Stephenson’s modified theory of 1956?

A
  • Modified dose-response theory
  • Drug response depends on both the affinity and efficacy.
  • Describe “spare receptors”. This suggests that a maximal response can be achieved even if a fraction of receptors “spare receptors” are unoccupied.
43
Q

What is affinity?

A

Strength of binding between a drug and its receptor.

44
Q

What is dissociation Constant (Kp)?

A

The measure of a drug’s affinity for a given receptor.

The concentration of drug required in solution to achieve 50% occupancy of its receptors.

45
Q

What does agonist mean?

A

drugs which alter the physiology of a cell by binding to plasma membrane or intracellular receptors

46
Q

What is a strong agonist?

A

Agonist which causes maximal effects even though it may only occupy a small fraction of receptors on a cell

47
Q

What is a weak agonist?

A

Agonist which must be bound to many more receptors than a strong agonist to produce the same effect

48
Q

What is an antagonist?

A

Inhibit or block actions caused by agonist

49
Q

What is a competitive antagonist?

A
  • Competes with agonist for receptors

- Can be overcome by high doses of agonists

50
Q

What is a noncompetitive antagonist?*

A

Binds to a siteother than the agonist-binding domain. Induces a conformational change in the receptor such that the agonist no longer “recognizes” the agonist-binding domain.

51
Q

What does surmountable

and insurmountable mean?

A

Surmountable: Antagonism being overcome by high doses of agonists.

Insurmountable: even at high doses of agonist, they can not overcome the antagonism

52
Q

What does efficacy mean?

A

Degree to which a drug is able to cause maximal effects

53
Q

What does potency mean?

A

Amount of drug required to produce 50% of the maximal response that the drug is capable of causing

54
Q

What does effective concentration 50% (EC50%) mean?

A

Concentration of drug which induces a specified clinical effect in 50 % of the subjects to which the drug is administered.

55
Q

What does lethal dose 50 % mean?

A

Concentration of drug which induces death in 50% of the subjects to which the drug is administered

56
Q

What is the therapeutic index?

A

Measure of the safety of a drug

Calculated by dividing the LD50 by ED50

57
Q

What is margin of safety?

A

Margin between therapeutic and lethal doses of a drug

58
Q

What does addition mean in drug interaction?

A

the response elicited by combined drugs is EQUAL to the combined responses of the individual drugs

59
Q

What does synergism mean in drug interaction?

A

The response elicited by combined drugs is GREATER THAN the combined responses of the individual drugs

60
Q

What does potentiation mean in drug interaction?

A

Drug which has no effect enhancing the effect of a second drug

61
Q

What does antagonism of drug interaction mean?

A

Drug inhibits the effect of another drug, usually the antagonist has no inherent activity

62
Q

CYP substrate + CYP inducer = _______ amount of substrate due to ______

A

reduced

increased metabolism

63
Q

CYP substrate + CYP inhibitor = _______ amount of substrate due to ______

A

increased

reduced metabolism

64
Q

What is steady state?

A

rate in= rate out

amount of a drug administered over time= amount of drug eliminated during the same time

65
Q

What is context sensitive half time?

A

For continuous infusion medication- the time until medication plasma levels reduce by 50% after stopping a continuous infusion

66
Q

What are some age related PK changes for the elderly?

A
  • Reduced absorption via carrier proteins
  • Reduced first pass metabolism
  • Higher body fat: water ratio*
  • Possible reduced albumin concentration and/or increased alpha-1 acid glycoprotein**
  • Reduced phase 1 metabolism
  • Reduced kidney fx
  • Disease states, thinning BBB*, GI tract changes
67
Q

What are some age related PK changes for neonates and infants?

A
  • Higher gastric pH, longer emptying time
  • Higher body water: fat ratio* (opposite peds)
  • Reduced/immature CYP450 enzymes**
  • Reduced protein binding
  • Reduced renal clearance
68
Q

Dialysis provides an average CrCl ~___mL/min

A

30mL/min

69
Q

What will be removed in dialysis?

A
  • Unbound volume < 3.5L/kg
  • Dosing interval longer than 1/2 life
  • Molecular weight <1000 daltons

(unbound, small, more ionic)

70
Q

What is a Partial Agonist?

A

A drug which fails to produce maximal effects, even when all receptors are occupied

71
Q

What is an Inverse Agonist?

A

Binds to receptor site and causes the opposite effect of an agonist (doesn’t block anything)

72
Q

Pregnancy Catergories

A

A- adequate well-controlled studies, no risk
B- Animal studies- no SE, no human studied
C- potential benefits may warrant use of the drug in pregnant women despite potential risks
D- +evidence of human fetal risk, but potential benefits may warrant use
X- animals/humans have + fetal abnormalities

Pharmacology (10 decks)

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