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Pharmacology - Exam 1 > Pharmacokinetics > Flashcards

Pharmacokinetics Flashcards

1
Q

Pharmacokinetics involves

A
  • Absorption
  • Distribution
  • Elimination (excretion, metabolism)
  • Steady-state concepts
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2
Q

Define Pharmacology

A

Study of drugs; interaction between the body/drug

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3
Q

Pharmacological effects of Drug concentrations

A
  • Therapeutic (positive)
  • Toxic (Negative)
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4
Q

Pharmacodynamics relationship with body/drug

A

Is what the drug does to the body

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5
Q

Pharmacokinetics relationship with body/drug

A

Is what the body does to the drug

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6
Q

Pharmacokinetics is

A

The relationship between dosage regimen and drug concentrations

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7
Q

Pharmacodynamics is

A

The relationship between drug concentrations and their pharmacological effects

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8
Q

Pharmacokinetic relationship with a Drug A, vs adding another drug

A
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9
Q

Pharmacodynamic relationship of drug concentration and pharmacological effects

A

Middle square is Toxicity

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10
Q

How pharmacodynamics and pharmacokinetics are related

A
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11
Q

Pharmacokinetic interaction: Changes in outcome are the result of changes in the relationship between the _______ and the _____________

A
  • DOSE
  • Concentration
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12
Q

Pharmacokinetic interaction: The pharmacologic effect has changed as a result in a change in the _________________________.

A

Change in drug concentration

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13
Q

Pharmacodynamic interaction: Changes in outcome are the result of changes in the relationship between the _______________ and the _________.

A
  • Drug concentration
  • Effect
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14
Q

Pharmacodynamic interaction: The pharmacologic effect has changed despite a lack of change in the __________________________.

A

Drug concentration

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15
Q

Functions of Cell membrane

A
  • Barrier to drugs
  • Divides the body into compartments
  • More lipid-soluble substances move more freely across membranes
  • less lipid soluble substances pass less freely across membranes
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16
Q

Examples of less lipid-soluble substances (cell membrane)

A
  • polar substances
  • relatively lipid-insoluble
  • ionized substances
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17
Q

What is absorption bioavailibily

A
  • Measure of the amount of drug that is BIO AVAILABLE
    (i. e. available to exert a systemic effect on the body)
  • Measure of systemic drug exposure
    (i. e. how much a drug is absorbed)
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18
Q

What is Absolute bioavailability

A

How much drug is absorbed

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19
Q

Relative and absolute bioavailabilty combined

A

How two dose forms compare in terms of systemic drug exposure

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20
Q

What kinetic parameter quantifies drug exposure?

A
  • The AUC produced by the serum concentration-vs-time profile
  • Expressed % of product which reaches the systemic circulation
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21
Q

How does this chart explain bioavailability?

A

-Bigger the area under the curve the more bioavailability (drug in systemic circulation)

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22
Q

Bioavailability depends on the:

A
  • absorption characteristics of the drug and dose form
  • metabolism occuring prior to the drug reaching the systemic circulation
    (i. e. first pass effect)
  • presence of interacting substances
    (i. e. drugs, food/no food/type of food)
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23
Q

Why you calculate absolute bioavailability

A
  • Know how much drug is absorbed/reaches systemic circulation
  • How the two dose forms compare in terms of systemic drug exposure
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24
Q

Purpose of relative bioavailability

A

To calculate/approximate the bioavailability relating to drugs

i.e. Tablet relative to solution

or

Solution relative to tablet

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25
Q

Comparison of bioavailability and relative bioavailability

A

All measure of bioavailability could be called measures of relative bioavailability.

-Compare AUC of 1 product RELATIVE to another

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26
Q

If bioavailability comparison is to a product with absolute (100%) absorption what type of bioavailability is it?

A

ABSOLUTE

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27
Q

If bioavailability comparison is to a product with less than absolute (100%) absorption what type of bioavailability is it?

A

RELATIVE

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28
Q

Based on this chart, which drug would you choose? PO or IV

A

Because the AUC is similar, the pharmacist could choose PO or IV

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29
Q

What is the effect of different conditions on drug bioavailability

A

The approximate bioavailability of a drug administered on an empty stomach RELATIVE to its administration with food:

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30
Q

What does it mean if value is over 100

A

That fasting is more bioavailable

31
Q

What does it mean if value is under 100

A

More bioavailable with food

32
Q

What is volume of distribution

A

To account for observed initial drug concentrations following drug administration, researchers calculate an “apparent” volume

-It is NOT a true physiologic volume

33
Q

In terms of compartments, what is the central pool aka the blood stream

A

The central compartment

34
Q

In terms of compartments, what is the pools with different cells

A

The peripheral compartments

35
Q

Which compartment do you take measurements from?

A

The central compartment

36
Q

Volume of distribution is increased with

A
  • Drugs that have a higher lipid solubility
  • Drugs that have lower protein binding
  • Drugs that have greater tissue binding
37
Q

Why do drugs that have higher lipid solubility have increased volume of distribution?

A

They can go further than lipid insoluble because they can cross cell membrane

38
Q

Why do drugs that have lower protein binding have a increased volume of distribution?

A

More free molecules and can move out of the central compartment

39
Q

Why do drugs that have greater tissue binding have an increased volume of distribution?

A

They leave the central compartment and have increased tissue affinity, they are unlikely to come back to the blood stream readily

40
Q

How do we use Volume of Distribution

A
  • Determining drug doses
  • Provide clinicians with a sense of the spaces/areas/compartments into which the drug distributes
    (i. e. extent of drug distribution/where it is going to be in body)
41
Q

Formulas for determining doses?

A
42
Q

Describe Distribution Spaces

A
  • Volume of Distribution measured in L/Kg (body weight) or L
  • Drugs can be roughly categorized according to their volume of distribution
    i. e. < .25 L/kg has a small VD (spends less time in central compartment, and therefore is affected by hydration levels)

>.70 L/Kg (spends most time in peripheral compartment, these drugs are well dialyzed)

43
Q

Small Vd concentrates where?

A

-Concentrates in ECF (central compartment)

44
Q

Mid range VD is found in what compartment

A
  • Black: within cells/tissue bound (peripheral compartment)
  • White: Extracellular fluid (central compartment)
45
Q

Large VD concentrates in what compartment

A

-Concentrates in cells/tissues (peripheral compartment)

46
Q

Describe volume of Distribution, Pool analogy

A

Same amount of a two different drugs, with completely different distributions

47
Q

Describe volume of Distribution, Patient analogy

A

Drugs react differently with every patients, take their size into consideration

48
Q

Drug Elimination two forms

A
  • Biotransformation
  • Excretion
49
Q

Drug Elimination Biotransformation is

A

Drug is chemically altered to form a metabolite that is more “excretable” than parent drug

50
Q

Drug Elimination Excretion is

A

Removal of a drug or a metabolite from the body via the organ

51
Q

What organ excretes drugs

A

kidneys

52
Q

Which substances are more ready for renal excretion?

A

Lipid insoluble

(less time in periphery, more time in central compartment)

53
Q

What organ is where biotransformation occurs?

A

Liver

54
Q

Biotransformation Phase I reactions on drugs

A
  • Introduce functional groups (OH, -COOH, -SH, -O-, or -NH2) to prepare for Phase II reactions
  • these reactions often lead to drug inactivation
55
Q

What is the most common phase I reaction in biotransformation

A

Oxidation

56
Q

What is Oxidation

A
  • most common Phase I reaction
  • Mediated by cytochrome P450 enzymes
  • Most sensitive to changes in liver function
    (i. e. smoking, alcohol, aging)
  • Reduction
  • Hydrolysis
57
Q

What is Phase II reactions in biotransformation

A
  • drug or metabolite is conjugated to glucuronic acid, methyl group, acetyl group, sulfate group
  • these reactions produce a metabolite which is less lipophilic (more polar)
  • Enzymes are less susceptile to change in liver function
58
Q

What is the half life of a drug?

A

of a drug is the measure of how long it takes for half of a drug to be eliminated from the bloodstream.

59
Q

What is clearance?

A

The rate of elimination of substances from the blood

60
Q

in Dose-serum concentration relationships:

For a drug whose elimination processes are NOT easily maximized (PK verbiage=NOT easily saturated), the elimination rate of that drug increases in _______________ to the serum drug concentration (referred to as ______________). For such a drug, the serum drug concentrations produced are ______________ to the dose administered.

-Half life is independent of drug concentrations

A
  • Direct proportion
  • 1st order elimination
  • directly proportional
61
Q

In first order elimination what is this graph going to look like?

A

LINEAR

62
Q

In 1st order elimination what does this graph look like?

A

Linear

63
Q

The proportionality of serum concentration in 1st order elimination for IV and Oral

A

Holds true for IV drugs

May not hold true for oral drugs (absorption may decrease with different doses)

64
Q

For oral administration what do these graphs show

A

Body can only absorb so much of the drug!

65
Q

in Dose-serum concentration relationships:

For a drug whose elimination processes ARE easily maximized (PK verbiage= easily saturated), the elimination rate of that drug is ________. This is referred to as _________________. For such a drug, the serum drug concentrations produced are ___________ to the dose administered. Small increases produce large increases serum drug concentrations

-Half life is DEPENDENT of drug concentrations

A
  • Constant
  • Zero order elimination
  • Disproportional
  • Large
66
Q

Zero order elimination graph look like

A

Increases and then plateaus (non-linear)

67
Q

Zero order elination graph looks like

A

increases non linearly

68
Q

What is important to remember about zero order drugs

A

BE CAREFUL

These drugs are disproportional to the dose admninstered

Most drugs are NOT eliminated in this manner

69
Q

How many Half lives to get to steady state

A

4-7 half lives

(5 is common)

70
Q

At steady state, what is the relationship between the rate of drug going into a patient and the rate of drug leaving the patient?

A
  • the rate of drug going in = the rate of drug going out
  • the amount of drug eliminated over the dosing interval = the dose administered
71
Q

What is happening with regard to drug accumulation during steady-state?

A

Drug accumulation reaches an equilibrium (acccumulation isnt occuring any further)

72
Q

Name factors that can cause a patients drug regimen to be “knocked out” of steady state?

A

Anything that changes the input or output

(then needs to go through half lives again to stabilize)

73
Q

Primary determinant of how long it will take for a drug regimen to reach steady-state?

A

The time to reach steady-state is dependent on the drugs half life

Pharmacology - Exam 1 (4 decks)

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