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Pharmacokinetics > ADME > Flashcards

ADME Flashcards

1
Q

Explain Plasma Concentration vs. Time

A
  • Non-IV route
  • Onset, duration, peak plasma concentration
  • Therapeutic range or window
  • Narrow vs broad

-Drug level monitoring
trough - lowest concentration/more dose
peak - highest concentration/no dose

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2
Q

What is Pharmacokinetics

A

Effects of BODY on the DRUG

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3
Q

What is Pharmacodynamics

A

Effects of DRUG on the BODY
(include pharmacological effects)

  • —-Therapeutic
  • —-Toxic
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4
Q

What are the four processes of pharmacokinetics

A
  • Absorption
  • Distribution
  • Metabolism
  • Excretion
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5
Q

Can drugs overcome barriers?

A

Drugs overcome many barriers to reach site of action (Physical and chemical)

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6
Q

Explain how all 4 proceses of PK are involved in drug movement.

A
  • Drugs must enter bloodstream
  • It must leave the vascular system to reach sites of action
  • Must cross membranes to undergo metabolism and excretion
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7
Q

What is the cell membrane structure

A
  • Hydrophobic tail (lipid)

- Hydrophilic head (water loving)

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8
Q

Pass vs between cell membrane

A

Drugs must usually pass through the cell vs. between them

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9
Q

How do drugs cross the cell membrane

A
  • Pores and Channels
  • Transport systems
  • Direct penetration of the membrane
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10
Q

Pores and Channels

A
  • Small and specific
  • Na+, K+ ions
  • A lot more electrolyte related
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11
Q

what are transport systems and name an example

A
  • Move drugs from one side of cell membrane to another side

* Example: P Glycoprotein

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12
Q

What are glycoproteins and where are they located

A

They transport drugs OUT of cell.

  • Intestines
  • Kidney
  • Liver
  • Placenta
  • Brain
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13
Q

How can drugs directly penetrate through the cell membrane?

A

They must be lipophilic

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14
Q

What happens if drugs are not lipophilic

A

if they are not lipid soluble they cannot penetrate the membrane (polar and ions)

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15
Q

In what case would you need to give a LIPID ONLY Med to a patient?

A

If they are in severe pain and need immediate drug effects

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16
Q

What are polar molecules

A
  • no net charge
  • uneven distribution of charges
  • water (H+, O-)
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17
Q

What are ions

A
  • net electrical charge
  • Either positive or negative
  • Unable to cross membrane
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18
Q

what is ionization

A

the process for acid and base to be converted to a charged particle

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19
Q

What type of environment would cause a weak acid to become a charged ion?

A

Basic Environment

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20
Q

What type of environment would cause a weak base to become a charged ion?

A

Weak Environment

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21
Q

Weak acids

A

proton donator

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22
Q

Weak bases

A

proton acceptor

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23
Q

Drugs can either be??

A

Either weak acid or weak base

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24
Q

pH-dependent ionization

A

some drugs can exist in either charged or uncharged forms

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25
Q

If ions are unable to cross membranes what is the solution?

A

pH-dependent ionization

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26
Q

Charge vs. uncharged forms depende on?

A

pH and ionization constant of drugs

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27
Q

Acidic drugs tend to ionize where?

A-

A

In basic pH environment

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28
Q

Basic drugs tend to ionize where

BH+

A

In acidic pH environment

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29
Q

What is Ion trapping

A

-It is a manipulation of pH of different fluids to create this ion trapping effect.

in other words, unionized form changes to changes to Ionized form and is trapped and cannot cross.

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30
Q

Why can’t the ionized part of the drugs cross the membrane?

A

They are charge and attract water molecules thus forming larger molecules making them less lipid soluble

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31
Q

What drugs can easily cross membrane?

A

Unionized drugs

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32
Q

Is aspirin acidic or basic?

A

-Acidic (salicylic acid)

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33
Q

Where would Aspirin absorb from?

A

GI Tract

pH is at 1

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34
Q

What happens to the pH of your GI tract as aspirin moves along from stomach to intestines?

A
  • The pH of the GI tract as it moves along from the stomach to the intestines will become more basic.
  • It is able to cross cell membrane into blood stream
  • As it gets to basic environment, it will become ionized and can no longer cross cell membrane. It gets stuck in the plasma
  • As it reaches its basic environment less of the drug is absorbed so to overcome we give larger doses of aspirin
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35
Q

Name the four “enteral” routes of administration

A
  • Oral
  • Rectal
  • Sublingual/buccal
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36
Q

What are the advantages of oral route of administration?

A
  • Most convenient

- Economical (Inexpensive)

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37
Q

What are the disadvantages of oral route of administration?

A
  • First pass effect
  • Patient compliance
  • Irregular absorption (influence of food or medications)
  • Many formulations
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38
Q

What are the advantages of rectal route of administration?

A
  • Hepatic first-pass effect (less than oral)

- Useful for pediatrics, vomiting, or unconscious patients

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39
Q

What are the disadvantages of rectal route of administration?

A

-Erratic absorption (highly vascularize can’t predict absorption time)

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40
Q

What are the advantages of sublingual/buccal administration?

A
  • Rapid onset of drug effect.
  • Absorption into venous circulation
  • It bypasses hepatic (the liver), and avoids first pass effect.
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41
Q

Where are oral drugs mostly absorbed, regardless of ionization, and why?

A
  • Absorbed via GI tract

- Larger surface area and better blood flow.

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42
Q

Name the 6 “parenteral” routes of administration

A
  • IV
  • Intramuscular (IM)
  • Subcutaneous
  • Inhalation
  • Transdermal
  • Topical
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43
Q

What are the advantages of IV administration?

A
  • Rapid Onset
  • Reliable
  • Bioavailability 100%
44
Q

What are the disadvantages of IV administration?

A
  • Irreversible
  • need for patient IV access
  • narrow therapeutic window
45
Q

What are the advantages of IM

What are the disadvantages

A
  • Depot delivery possible

- Painful

46
Q

What are the advantages of subcutaneous

What are the disadvantages

A

Smaller volume

Slower onset vs IM

47
Q

What are the advantages of Inhalation

What are the disadvantages

A
  • Rapid Onset

- Less systemic exposure

48
Q

What are the advantages of transdermal administration?

A
  • Simple, convenient, painless
  • prolonged action
  • improved compliance (birth control patch)
  • Systemic Delivery
49
Q

What are the disadvantages of transdermal administration?

A

-May be irritating to skin

50
Q

Topical

A

Skin, otic, nasal, vaginal

Less systemic exposure

51
Q

Explain parenteral routes

A
  • They avoid 1st pass

- They don’t go through absorption they go straight into the distribution phase

52
Q

What is absorption

A

Drug moves from site of administration to systemic circulation

53
Q

What are a few factors that affect absorption

A
  • First pass effect
  • % of uncharged form
  • Blood flow (can cause slow absorption)
  • Pgp-multidrug REVERSE/EFFLUX transporter
  • Surface area (villi of sm intestines)
  • Contact area (severe diarrhea)
  • Food
54
Q

Why does the solubility of a drug matter in relation to drug absorption?

A

More lipid soluble, aka lipophilic (lipid LOVING) can pass through cell membranes easily

55
Q

What effect does ionization have on drug absorption?

A

Drug absorption is greater if the drug is in non-ionized, lipid soluble form. The ionized form is water soluble and possesses an electrical charge which is repelled by the cell membrane.

56
Q

What is the first pass effect?

A

Drugs absorbed from the GI tract enter the portal vein and pass through the liver before entering circulation.

57
Q

What are the disadvantages of the “first pass effect”?

A
  • Decrease drug to body
  • Decrease bioavailability
  • May require alternate route of administration
58
Q

Define bioavailability

A
  • The fraction of dose that reaches the systemic circulation / quantity of drug administered
59
Q

What factors affect bioavailability

A
  • First pass effect
  • Formulation
  • Chemical Characteristics
  • P-glycoprotein reverse transporter
60
Q

What is distribution?

A

Drugs move from systemic circulation to tissues

61
Q

What are a few factors that affect distribution?

A
  • Drug Characteristics (crossing membranes)
  • Blood flow
  • Capillary Permeability
  • Blood Brain Barriers (BBB)
  • Plasma Protein Binding (PPB)
  • Patient and disease factors (obesity, fluid accumulation)
62
Q

What are blood brain barriers

A
  • they favor lipophilic, small molecules
  • tight junctions
  • So only drugs that are lipid soluble or have a transport system can cross BBB
  • low Plasma Protein Binding
63
Q

What are Plasma Protein Binding?

A

Drug binding proteins

64
Q

What is the most common type of drug binding protein

A

Albumin

65
Q

What makes albumin so special?

A
  • Prevalent protein

- Most drugs bind to it

66
Q

Describe the characteristics of PPB

A

Reversible (drugs may be bound or unbound)

Free drug (active)

Bound drug (inactive)

67
Q

Name a few factors that affect PPB

A
  • nutritional status (poor diet results in a decrease in albumin)
  • plasma protein levels (the availability of albumin)
  • Displacement (possible drug to drug interaction)
68
Q

What is elimination?

A

Removal of drug from body

69
Q

What components does elimination include?

A

Metabolism and Excretion

70
Q

Name a few factors that affect Elmination

A
  • Renal function
  • hepatic function
  • Genetic Variations
  • Concomitant meds
  • Age
71
Q

Describe metabolism

A
  • Also known as biotransformation

- Enzymatic alternation of drug structure

72
Q

Where does metabolism occur?

A
  • MOSTLY in the liver

- Also in GI tract, lungs, skin, kidneys

73
Q

How does metabolism occur

A

Through enzymes!

74
Q

What does metabolism do to drugs

A

Makes the drugs more polar/H2O soluble

75
Q

What are CYP450 Enzymes

A
  • Large family of enzymes
  • Catalyze oxidation rns
  • Families 1,2,3
76
Q

Drug interactions

A

CYP450 Enzymes

77
Q

Characteristics of CYP450 Enzymes

A
  • responsible for 70-80 % of drug metabolism
  • There are 57 CYPS in humans
  • Synthesis of steroid hormones, bile acid.
  • Influence expression or function
78
Q

Name the different components of metabolism

A

Substrate
Metabolite
Pro-drug

79
Q

What are metabolites? Name them

A

Product of transformation

 - Inactive metabolite - active to non-active
 - Active metabolite - non-active to active
 - Toxic metabolite
80
Q

Describe what is a pro-drug

A

Inactive drug that undergoes METABOLISM to ACTIVE form

81
Q

What happens if the drug is not active?

A

No activity on body until it i has been metabolize to in an active form

82
Q

Name a few factors that affect metabolism?

A
  • Age
  • Sex
  • Genetic Variations
  • Diet (GRAPEJUICE, CHAR GRILLED)
  • Smoking occupation
  • OTHER DRUGS (drug to drug interaction)
83
Q

Is pro-drug a product of metabolism?

A

NOOOO

84
Q

What is Induction?

A
  • Drugs can induce enzymes!
  • Increase transcription
  • Increase # CYP450 enzymes to work harder
  • Increases rate of drug metabolism
  • Results in decrease of plasma drug levels
85
Q

What is a an inhibitor

A
  • Decreases rate of drug metabolism
  • Leads to increase adverse effects & toxicity
  • AKA drug accumulation
86
Q

What is a competitive inhibitor

A
  • Drug competes with another drug for enzyme spot
  • can decrease rate of which one or both agents are metabolized
  • Drug accumulation
87
Q

What is a irreversible inhibitor

A

No matter what you do, Drug I will never get off the CYP450 enzyme.

88
Q

Describe Excretion

A

Removal of drug or drug metabolites from body

89
Q

Where does excretion take place?

A

KIDNEYS

-GI tract (bile), lungs, skin, Lungs

90
Q

Name a few factors that affection excretion

A
  • impaired renal function

- Age

91
Q

Name the renal excretion steps

A
  1. Glomerular Filtration
  2. Passive Tubular Reabsorption
  3. Active Secretion
92
Q

What happens during the Glomerular filtration phase?

A
  • Moves drugs from blood to urine

- Blood cells, large proteins and albumin bound DO NOT GET FILTER BACK

93
Q

What happens during the Passive Tubular Filtration phase?

A
  • As drugs are being filtered into urine, drug concentrations in the blood are lower than drug concentration in the tubule (urine)
  • Passive diffusion of lipophilic drugs diffuse back into bloodstream
  • Ion and polar compounds (non-lipid soluble) are excreted in urine
94
Q

What happens during the Active Secretion phase?

A

The active transport of tubules pump organic acids and bases from blood to urine

95
Q

What are elimination patterns and what does it include

A

-1st order of elimination - most drugs

a constant fraction % will be eliminated

-Half-life (t½ )

96
Q

What are half-life?

A
  • It is the time it takes to eliminate 50% of a drug from the body
  • unique half life for each drug
  • determines duration of action and dose interval

helps us figure out “how long will the drug last” and when do we need to redose patients

97
Q

About how many half-lives does it take to clear a single dose from the body for a drug

A

check powerpoint

98
Q

For a drug with half - life 24 hr, about how long will it take to leave the body after a single dose?

A

checkpower

99
Q

If we have a long half-life….

A

we don’t have to give doses frequently because they leave body slowly

100
Q

If we have a short half-life……

A

we need to give does frequently because they leave body quickly

101
Q

What is steady state?

A

steady = equilibrium

Rate going in = rate going out

102
Q

What causes drugs levels to reach plateau?

A

When the amount of drug eliminated between doses equals the dose administered, average drug levels will remain constant and plateau will have been reached

103
Q

Maintenance dose (no loading dose)

Oral dosing

A
  • Takes longer to reach MEC since plasma concentration builds up slowly (good route)
  • Not appropriate for cases of an emergency
104
Q

Loading dose

Oral dosing

A
  • Shorter time to get to therapeutic response (to reach MEC quicker)
  • Appropriate in serious conditions or emergency situations where the need us a drug is to effective immediately
105
Q

To achieve a steady state you need how many half lives?

A

4 to 5 half lives

106
Q

Large volume of distrubtion

A

With some drugs, especially those with a large volume of distribution, it may be necessary to give a loading dose (a big dose) initially to get above the minimum effective concentration and get the beneficial effect quickly.

Pharmacokinetics (6 decks)

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