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Introductory > Pharmacokinetics lecture > Flashcards

Pharmacokinetics lecture Flashcards

5/31/19

1
Q

Pharmacokinetics

A

Foucsed on how drugs are handled in the body from the time they enter to elimination

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2
Q

4 main processes of pharmacokinetic events

A

1) absorption - entrance of drug into blood stream
2) distribution - moving from blood stream into tissues of body
3) metabolism - physical and chemical alterations that a substance undergoes in the body
4) excretion - eliminating waste products of drug metabolism

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3
Q

Plasma drug concentration time curve (time response curve)

A

For most drugs, there is a direct correlation between therapeutic and toxic responses and the amount of drug present in plasma, therefore the plasma drug conc. can be determined to theorize the impact it is having at its site of action (which typically cannot be measured)

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4
Q

Onset of action

A

T0 to T1, btwn administration and time effect begins at the MEC

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5
Q

Duration of action

A

T1 to T3, lengh of time to which the drug is above the MEC

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6
Q

Time to peak

A

T0 to T2, time for peak action of the drug

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7
Q

Drug absorption is bypassed by drugs that are administered via…

A

…directly in the blood stream

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8
Q

Drug characteristics that make it easier to be absorbed

A
  • More lipid soluble

- More nonpolar

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9
Q

Common sites of absorption of drugs

A

1) mucosa of stomach, mouth, small intestine, or rectum
2) Blood vessels in muscles or subcutaneous tissues
3) dermal layer

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10
Q

Lipid bilayer

A

Impermeable to water and other non lipid soluble substances, may allow passage of small molecules through channels or transporters

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11
Q

Most common mechanism of drug absorption

A

passive diffusion

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12
Q

Fick’s law

A

sdfsd

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13
Q

Facilitated transport

A

Passive process to carry drug molecules passively down a conc. gradient facilitated through a carrier molecule

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14
Q

Active transport

A

Requires ATP and carrier molecules to move a drug from a low to high conc area in an active process

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15
Q

Endocytosis

A

Minor method by which some drugs are transported into cells

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16
Q

Route of drug administration

A

Determine rate and efficiency of absorption, depend on the physical and chemical properties of the drug, intended site of action, and desired onset

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17
Q

Oral administration

A

Used whenever possible, safest and most convenient route, onset of action is 30-60 min, most absorption occurs in small intestine, drug enters liver and can be metabolized

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18
Q

First pass effect

A

Occurs when a drug is largely metabolized by the liver before reaching systemic circulation, often requires administration of higher dose as a result

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19
Q

Sublingual administration

A

Used whenever rapid effects are needed, absorption directly through oral mucosa into blood stream, few minute onset of action, avoids first pass

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20
Q

Rectal administration

A

Often used when a localized effect is needed or another route is not feasible (unconscious or vomiting), onset is 15-30 min, retention varies by patient

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21
Q

Disadvantages of alimentary administration

A

Rate of absorption varies, can be a problem if small range in blood levels separates desired therapeutic and toxic effects, patient compliance is not ensured, first pass effect

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22
Q

Parenteral administration

A

Sterile injection of a drug such as intraveonous, subcutaneous, intramuscular, etc

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23
Q

Intravenous administration

A

Bypasses absorption barrier, onset in several minutes, insoluble drugs cannot be delivered via IV

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24
Q

Subcutaneous administration

A

Often done for drugs inactivated by stomach, action is several minutes

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25
Q

Intramuscular administration

A

Onset of several minutes, provide sustained drug injection over period of time

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26
Q

Advantages of parenteral administration

A

More rapid response time, dose can be more accurately delivered, feasible when alimentary path not possible, large volumes can be administrated

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27
Q

Disadvantages of parenteral administration

A

Rapid absorption can lead to adverse effects, sterile formulation and aseptic technique. local irritation at site of injection, not suitable for insoluble substances

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28
Q

Topical administration

A

Most oitments, gels, creams are applied to skin, eye or ear for local effects with onset of 1 hour, systemic absorption is relatively minimal

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29
Q

Transdermal drug deliver systems

A

Provide continuous drug delivery (nicotine patches, birth controls)

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30
Q

Inhalation administration

A

Lungs have large surface for absorption with onset within 1 min, effects can be local or systemic

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31
Q

Intranasal administration

A

DRug absorption can cause either local or systemic effects

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32
Q

Vaginal administration

A

Local effects with onset of 15 minutes

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33
Q

Most drugs are ______ acids or _____ bases

A

Weak, weak

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34
Q

Weak acids are more likely to be absorbed where and why?

A

In the stomach, because it has a very low pH

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35
Q

Weak bases are more likely to be absorbed where and why?

A

The duodenum because it has a neutral pH 5-7

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36
Q

Drugs that affect the pH of the intestine can have an impact on…

A

…other drugs that need to be absorbed

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37
Q

Presence or absence of food in stomach

A
  • Food in stomach tends to slow absorption due to slower emptying of stomach
  • Some foods may interact with drugs, preventing or greatly reducing absorption
  • Some medications can be irritating to the stomach but buffered by food
38
Q

Drug formulation (solubility)

A
  • Tablets and capsules require time for dissolution to occur
  • Liquid generally absorbed faster
  • Smaller size of drug particle, faster rate of dissolution and absorption
39
Q

Decreased intestinal motility can result in…

A

…prolonged contact of drug with mucosa and therefore increased absorption

40
Q

Bioavailibility

A

Amount of drug dose that reaches the systemic circulation ex) if 100mg administered and 50mg reaches blood stream, 50% bioavailable

41
Q

Determination of bioavailability

A

Comparing plasma levels of drug after particular route of administration compared to levels achieved by injection, which has a bioavailibility of 100%

42
Q

Bioavailability determination

A
  • physical and chemical characteristics of the drug

- formulation

43
Q

Bioequivalence

A

Indicates that a drug in two or more similar dosage forms reaches the general circulation at the same relative rate to the same relative extent

44
Q

A rated drug

A

FDA has named the generic drug as therapeutically equivalent to the brand name drug

45
Q

B rated drug

A

FDA has named the generic drug has bioequivanlent problems to the brand name drug

46
Q

AB rated drug

A

FDA has named the genric drug has bioequivlanet problems to the brand name drug that has been resolved by evidence and study to be therapeutically equivalent

47
Q

Therapeutic interchange

A

Different drugs that have the same pharmacological and or therapeutic effects

48
Q

example of therapeutic interchange

A

Ibuprofen (motrin) and naproxen (aleve)

49
Q

Factors that determine how much drug reaches any one organ or area

A
  • physical or chemical characteristics of drug
  • cardiac output
  • plasma protein binding
  • blood flow to tissues
  • Presence of specific tissue barriers
50
Q

Volume of distribution

A

Ratio of total drug in the body to the concentration of the drug in the plasma

51
Q

If Vd=42L, if Vd=5.5L

A

Drug is evenly distributed, drug is conc. in plasma

52
Q

If Vd>42L

A

Drug is sequestered in a depot, usually adipose tissue

53
Q

Plasma protein binding

A

Several different proteins in plasma can have drugs reversibly bind to them, ratio of bound/unbound varies on a drug by drug basis, bound drugs are pharmacologically inactive, protein binding drugs have a long duration of action, some drugs can displace others that bind protein

54
Q

Can disease states affect amount of protein binding?

A

yee

55
Q

Sites of drug storage

A
  • Adipose tissue (lipid soluble drugs)
  • Bone (tetracycline will bind calcium permanently)
  • Muscle
  • organs
56
Q

Drug elimination chemical alterations

A

Made inactive and more polar to improve ability to remove through kidney

57
Q

Importance of inactivation of drugs to allow for renal secretion

A

Without, it would take years to remove from the body

58
Q

Prodrugs

A

Compounds pharmacologically inactive as administered then undergoes conversion into active form while in the body

59
Q

Sites of metabolism of drugs

A

Primarily in the liver

60
Q

Phase 1 (nonsynthetic) metabolism

A

Function to increase polarity of drug molecule, a site for phase 2 metabolism as well, involves oxidation, reduction, and hydrolysis

61
Q

Phase 2 (synthetic) metabolism

A

Coupling of a drug or its metabolite with endogenous substrate to conjugate it and increase greatly the polarity and enhance secretion

62
Q

Oxidation, reduction, hydrolysis

A

Types of phase 1 metabolism, oxidation is most common

63
Q

Metabolic induction

A

When some drugs are taken repeatedly, they stimulate the drug microsomal meetabolizing syndrome, increasing the amount of enzymes and faster rate of drug metabolism, duration of action is decreased for all drugs metabolized by cytochrome P-450, formulates tolerance

64
Q

Metabolic inhibition

A

Some drugs inhibit rather than induce production of microsomal enzymes, excess drug may accumulate in the body and the dose requirement may need to be reduced to avoid toxicity

65
Q

Liver function and drug metabolism

A

Can see compromised drug metabolism abilities, newborns and fetuses lack microsomal enzyme system

66
Q

Renal excretion

A

Primary method of drug excretion, drug filtered through glomerulus, some are reabsorbed, but the more polar they are the less likely they are to be resorbed

67
Q

GI excretion

A

Certain drugs can enter the intestines by the way of the biliary tract, after being released in the intestines, can be absorbed into the blood again

68
Q

1st order kinetics

A

For most drugs is proportional to the plasma concentration, conc. of drug diminishes logarithmically with time

69
Q

zero order kinetics

A

Occurs when drug elimination does not change with time

70
Q

2 compartment model

A

f

71
Q

Clearance

A

Volume of plasma cleared of drug per unit time (ml/hr)

72
Q

2 major sites of clearance

A

1) liver (metabolic clearance)

2) kidneys (renal clearance)

73
Q

Goal of dosing interval

A

To dose within time frame so that drug levels remain in therapeutic range repeatedly for however long desired result is required

74
Q

Delayed release purpose

A

To create a dosing interval that gives a steady state concentration in the therapeutic zone

75
Q

Additive character of clearance

A

Dividing rate of elimination at each organ by conc. of drug presented to it yields the respective clearance of that organ, which can all summate to total clearance by the body

76
Q

If mechanisms of elimination become saturated….

A

…Then first order kinetics no longer is method of drug removal, zero order kinetics is

77
Q

Importance of plasma drug levels

A

Because it is impractical to measure a drug conc. at the site of action, there is a direct correlation btwn therapeutic or toxic dosages and amount of drug present in plasma.

78
Q

Minimum effective conc.

A

The lowest plasma drug levels for which therepeutic effects will occur - to be beneficial drug conc. must be at or above this value

79
Q

Toxic conc.

A

The plasma drug levels for which toxic effects will occur - to be beneficial drug conc. must be below this value

80
Q

Therepeutic range

A

Space between minimum effective conc. and toxic conc. that a drug can produce a therapeutic response

81
Q

Width of therapeutic range can vary. Why is this a problem?

A

A small therapeutic range dictates the ease at which a drug can be administered safely or not

82
Q

Plateau drug levels

A

When the amount of drug entering the body in the therepeutic range equals the rate at which it is being removed from the body

83
Q

Cpss max

A

Peak level of a dosing interval

84
Q

Cpss min

A

Trough level of a dosing interval

85
Q

Cpss avg

A

Avg concentration level achieved between the peak and trough of dosing interval

86
Q

Time required to achieve steady state is not based on _________, but rather requires ______

A

dosage size, 4-5 half lives to reach

87
Q

Continuous infusion

A

Drug administration technique that keeps plasma levels nearly constant

88
Q

Reducing dosage size and increasing frequency

A

Drug administration technique deccreases the fluctuation between dosages

89
Q

Age impact on drug metabolism

A
  • Fetus and premature infants lack drug metabolizing enzymes
  • Children can metabolize drugs more quickly than adults
  • elderly things fall apart
90
Q

Sex/race impact on drug metabolism

A

-Sex/race differences have been observed in some cases on ability to metabolize drugs

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