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MT6314 (PCOL) > PHARMACOKINETICS > Flashcards

PHARMACOKINETICS Flashcards

1
Q

It is the effects of the biologic system on drugs

A

Pharmacokinetics

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2
Q

It deals with the processes of absorption, distribution and elimination of drugs

A

Pharmacokinetics

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3
Q

True or False

Pharmacokinetics makes possible the calculation of loading and maintenance doses

A

True

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4
Q

What are the 4 components of Pharmacokinetics?

A
  • Absorption
  • Metabolism
  • Distribution
  • Excretion
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5
Q

Acidic drugs bind to ______

A

Albumin

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6
Q

Basic drugs bind to ______

A

Alpha 1 Acid Glycoprotein

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7
Q

More highly protein bound drug will displace the ____ protein bound drug

A

Less protein bound drug

Drug A dislodges Drug B from inert binding site = higher efficacy of Drug B

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8
Q

What are the two basic parameters (known absorption)?

A
  • Volume of Distribution (Vd)
  • Clearance (CL)

  • It is unique for a particular drug in a particular patient
  • It is average values in large populations that can be used to predict concentration
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9
Q

What is the formula for Volume of Distribution?

A

Vd = amnt. of drug in the body / plasma drug conc.

Units: Liters or Vd/kg

  • plasma drug conc. or conc. of drug in the blood
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10
Q

It is the concentration of a drug at the receptor site (in contrast to drug concentrations that are more rapidly measured, eg, blood)

A

Effective Drug Concentration

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11
Q

What are the determining factors on Plasma Concentration

A
  • Rate of Input (absorption) into the plasma
  • Rate of distribution to peripheral tissue (includin target organ)
  • Rate of elimination, or loss, from the body
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12
Q

It is the measure of apparent space in the body available to contain the drug

A

Volume of Distribution (Vd)

- It is the amount of drug in the body to the plasma/serum concentration

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13
Q

When a drug is avidly bound in peripheral tissues, it’s concentration in plasma may drop to very low values even if the total amount in the body is large

A

High volume of distribution (Vd)

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14
Q

When a drug is completely retained in the plasma compartment

A

Volume of distribution is equal to the plasma volume

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15
Q

It is the rate of elimination compared to plasma concentration

It depends on the drug and the organs of elimination in the patient

A

Clearance (CL)

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16
Q

What is the formula for Clearance (CL)

A

Rate of elimination of drug / Plasma Drug Concentration (Cp)

units = volume/unit time

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17
Q

Drugs are eliminated with what order of kinetics

A

First-order kinetics

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18
Q

What is the formula for elimination rate

A

Elimination rate = clearance (constant) x plasma concentration

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19
Q

True or False

For most drugs, Clearance is constant over the concentration range

A

True

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20
Q

Rate of drug concentration is ____ proportional to the concentration

A

Directly proportional

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21
Q

Clearance depends on the following factors:

A
  • Drug (1st order or 0 order kinetics)
  • Blood flow
  • Condition of the organs of elimination (extraction capability of the organ and drug delivery to the organ)
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22
Q

True or False

Elimination will be rapid at first and slow as the concentration decreases

A

True

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23
Q

What order of elimination is this?

Clearance is constant over broad range of plasma concentration

A

First-order elimination

50% units/h is eliminated through time (e.g. 5 units/h, 2.5, 1.25)

  • faster
  • as the conc. increases = the rate of elimination increases (vice versa)
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24
Q

What order of elimination is this?

Elimination rate is constant on plasma concentration

A

Zero-order elimination

e.g. 2.5 units/h is eliminated through time

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25
Q

It is the time it takes for the amount of concentration of a drug to fall to 50% of an earlier measurement

A

Half Life (t 1/2)

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26
Q

True or False

Half-life is dependent to the volume of distribution

A

True

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27
Q

Determines the rate at which blood concentration rises during a constant infusion and falls after administration is stopped

A

Half life (t 1/2)

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27
Q

True or False

Half life is a derived parameter from the volume of distribution and clearance

A

True

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28
Q

What is the formula of Half life?

A

t 1/2 = 0.693 x Vd / CL

Unit: time (hrs)

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29
Q

It is the average total amount of drug in the body which does not change over multiple dosing cycles

A

Steady State

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30
Q

The rate of drug administration is equal to rate of elimination

A

Steady State

Dose in = dose out

31
Q

Fraction/percentage of the administered dose of the drug that reaches the systemic circulation

A

Bioavalability (F)

32
Q

What is the formula for Bioavailability?

A

F = amnt of drug in the plasma / dose of drug administered

33
Q

What is a common measure of the extent of F?

A

area under the blood conc.-time curve (AUC)

34
Q

What is the bioavailability for Intravenous Administration (IV)?

A

F = 100% or unity

35
Q

What are the effects when drug is administered through other routes?

A
  • Reduced by incomplete absorption
  • 1st-pass metabolism
  • Distribution into other tissues before the target organ
  • Drug enters the systemic circulation
36
Q

True

Drugs are more absorbed in the small intestines because it has a larger surface area

A

True

37
Q

What are the factors affecting bioavailability?

A
  • Extent of absorption
  • First-pass effect (measured as the extraction ratio and is avoided by sublingual, transdermal, & rectal supp.)
  • Rate of absoroption (site of administration and formulation of drug)
38
Q

The following are to offset low bioavailability

A
  • Sublingual
  • Rectal-50% probability of bypassing the 1st-pass effect
  • Inhalation or nasal
  • Transdermal patches
39
Q

The AUC can be derived from?

A
  • single-dose studies
  • multiple-dose measurements
40
Q

What are the bioavailability of the following:
- Intravenous
- Subcutaneous
- Intramuscular
- Oral ingestion

A
  • Intravenous: F = 1 (by definition)
  • Subcutaneous: 0.75 < F < 1
  • Intramuscular: 0.75 < F < 1
  • Oral Ingestion: .05 < F < 1
41
Q

What is the absorption pattern of Intravenous route?

A
  • Absorption circumvented
  • Potentially immediate effects
  • Suitable for large volumes and for irritating substances, or complex mixtures, when diluted
42
Q

What is the absorption pattern of Subcutaneous route?

A
  • Prompt from aqueous solution
  • Slow and sustained from repository preparations
43
Q

What is the absorption pattern of Intramuscular route?

A
  • Prompt from aqueous solution
  • Slow and sustained from repository preparations
44
Q

What is the absorption pattern of Oral Ingestion route?

A
  • Variable, depends on many factors
45
Q

Time Course of Drug Effects

It is directly related to concentration
e.g. anticoagulants

A

Immediate Effect

46
Q

Time Course of Drug Effects

  • This happens due to distributional delay
  • Delayed expression of the physiologic
  • substance needed for the effect
A

Delayed Effect

47
Q

Time Course of Drug Effects

  • Constant infusion
  • Aminoglycosides causes renal toxicity if given constantly
  • Intermittent dosing only
A

Cumulative Effects

48
Q

Fraction or percentage of the drug removed from the perfusing blood during passage through the organ

A

Extraction ratio

Measure of the elimination of the drug by that organ

49
Q

Drugs with high hepatic extraction ratio have a large ______

A

1st-pass effect

50
Q

Desired therapeutic effects are produced in the _____

A

Target Concentration

51
Q

Goal is to achieve therapeutic levels: maximal effect, least toxicities

Plan for drug administration over a period of time

A

Dosing Regimen

52
Q
  • Dose needed to maintain a steady state of concentration
  • It is to maintain plasma concentration over periods of time
  • Enough drugs to replace eliminated drugs
A

Maintenance Doses

53
Q

Achievement of therapeutic levels of the drug in the body without exceeding the minimum toxic concentration

A

Dosing Regimen

54
Q
  • For drugs with long half-lives and longer time to reach a steady state
  • It is to achieve target plasma level rapidly/promptly

Volume of distribution (Vd) is important

A

Loading Dose

55
Q

What is the most important parameter in defining rational drug dosage?

A

Clearance

56
Q

Maintenance Dosage

What is the formula for Dosing Rate?

A

CL x desired plasma concentration / bioavailability

57
Q

Doses per day is determined by?

A
  • Half life
  • Therapeutic window

Maintain concentration higher than minimum therapeutic level at all time

58
Q

What is the formula for Loading Dose?

A

Vd x desired plasma concentration / bioavailability

If loading dose is large, the dose should be given slowly to prevent toxicity due to excessively high plasma levels during distribution phase

59
Q

In ____ , drugs are eliminated unchanged or as metabolites

Polar compounds are more efficiently eliminated

A

Excretion

60
Q

What is the most important organ in excretion?

A

Kidney

As well as Liver, GIT, Breast, Lungs

61
Q

It is the safe “opening” or range between the:
- Minimum therapeutic concentration
- Minimum toxic concentration

A

Therapeutic Window

62
Q

What determines the trough?

A

Minimum Therapeutic Concentration

63
Q

What determines the peak?

A

Minimum Toxic Concentration

64
Q

What are the variables of Pharmacokinetics?

A
  • Absorption
  • Clearance
  • Volume of Distribution
  • Half Life
65
Q

What pharmacokinetic variable is this?

  • Compliance of patient is important
  • Variation in bioavailability are usually due to variation in metabolism during absorption
A

Absorption

66
Q

What pharmacokinetic variable is this?

  • Most important parameter in designing dosage regimen
  • Creatinine clearance:
  • CREATININE CLEARANCE:
  • Good indicator of renal function
  • Adjust the dosage of the drug
  • Not reliable indicator for liver function
  • Estimated GFR as surrogate for Creatinine Clearance tests
A

Clearance

67
Q

Volume of Distribution

  • decreased Vd:
  • increased Vd:
  • increased Vd:
A
  • decreased Vd = binding to plasma proteins
  • increased Vd = binding to tissues
  • increased Vd = drug distributed to body waters, extracellular accumulation of body fluids
68
Q

No more increase in effect even if the concentration is increasing

A

Maximum Effect (Emax)

69
Q
  • Reflected by EC50 – concentration required to produce 50% of maximum effect
  • Increased, exaggerated response to small doses
A

Sensitivity

70
Q

When is the most appropriate time to measure drug concentration

A
  • Absorption is complete
  • 2 hours after the dose
71
Q

True or False

Under steady state concentration, condition in 3 to 4 t ½ must elapse before checking drug blood concentration

A

True

72
Q

Drugs given intermittently are in ______

A

steady state of concentration

73
Q

It used to determine the range of plasma levels that is acceptable when designing a dosing regimen

A

Therapeutic Window

74
Q

What is the absorption pattern of Oral Ingestion route?

A
  • Variable, depends on many factors

MT6314 (PCOL) (6 decks)

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