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Fundamentals Part 2 > Pharmacokinetics > Flashcards

Pharmacokinetics Flashcards

1
Q

What is one example of where only transcellular transport is used? (no paracellular)

A

capillaries in the blood brain barrier

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2
Q

List the equation used to calculate the pH of a weak acid

A

pH=pKa + log (A-/HA)

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3
Q

List the equation for the pH of a weak base

A

pH=pKa + log(B/BH+)

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4
Q

What occurs as pH=pKa

A

there is an equilibrium between the ionized and unionized forms of weak acids and bases

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5
Q

what is the equation for the volume of distribution Vd

A

Vd=amount of drug/concentration,

Vd=D/Co

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6
Q

what is the concept of the pH gradient

A

weak acids accumulate on more basic side of membrane & vice versa for bases

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7
Q

a coupled transport refers to:

A

a Secondary Active Transport carrier protein which uses an electrochemical potential difference to fuel transport

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8
Q

what is “controlled release” “extended release” or “sustained release”

A

to slow the dissolution, u can slow the absorption, in turn, prolonging the drug in the body system. Allowing for more uniform therapeutic effect while minimizing adverse effects

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9
Q

how does prolonging the duration of action effect the onset of action

A

it delays the onset

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10
Q

why would having a controlled/extended or sustained release be a problem

A

if treating someone was life-threatening where a rapid response is needed, you wouldn’t want the delayed onset of action that results from a controlled release

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11
Q

dissolution

A

for a drug to be absorbed it must 1st be dissolved in the fluid

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12
Q

how can you alter the rate of dissolution

A

coating it with wax or other water-soluble material, also complexing it with ion-exchange resins…altering the shape of drug, for example tablets dissolute slow, granules intermediate and fine particles are rapid

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13
Q

why is compliance easier for patients when you prolong the duration of action

A

patients only have to take drug twice a day vs. four, etc. (decreases frequency needed to take it)

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14
Q

under normal conditions how long would a drug be expected to stay in the stomach? small intestines? and Colin?

A

stomach: 2-4 hours, SI:4-10 and colonic tract: 12-50 hours

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15
Q

First-Pass Metabolism

A

when drug administered orally is absorbed into the blood stream and broken down by liver b4 reaching full systemic circulation

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16
Q

what types of factors affect bioavailability of a drug

A

insufficient absorption, decreased absorption, first-pass metabolism and other demographic factors (age, sex, exercise, genetics, stress, GI surgery)

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17
Q

what is measured by comparing the Area Under the Curve (AUC) after IV and oral administration to the plasma concentration over time

A

bioavailability

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18
Q

when the maximum (peak) plasma concentration is reached when:

A

drug elimination rate equals absorption rate

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19
Q

when does drug elimination begin

A

as soon as the drug enters the bloodstream

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20
Q

ADME stands for what referring to pharmacokinetics

A

Administration, Distribution, Metabolism, and Excretion

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21
Q

Molecular Weight

A

smaller passes easier, when females are lactating a larger drug would prevent it from accumulating in the breast milk

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22
Q

why are weak acids/bases IDEAL drugs

A

since they are present in both ionized and unionized forms, they can pass through lipid membranes or through water in body cause they transfer easily btw the two.

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23
Q

what is the bioavailability for a drug administered through an IV

A

100% (higher risk for adverse effects)

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24
Q

This type of pathway doesn’t require drug to be lipid soluble and no energy is required

A

paracellular pathway

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25
Q

what is the principle driving force for the paracellular pathway

A

hydrostatic pressure

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26
Q

why do we see a saturation point with facilitated diffusion vs. passive

A

only so many transporter proteins can work at one time…

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27
Q

why would it be wrong to give 1/5 the dose of a drug to a neonate based on the fact that they are 1/5 the weight of an adult when referring to body water

A

babies have more percent of body water than adults (75-80%) vs. adults 60 and elderly ~50%

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28
Q

acidic drugs tend to bind to plasma proteins. Describe it’s volume of distribution

A

Low

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29
Q

what is the main point to understand about perfusion rates affecting distribution…

A

more perfusion to the kidneys, lungs, heart, liver, and brain (Phase I) THAN the adipose, muscle, and skin (Phase II)

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30
Q

what are the two isoenzymes we should remember and % do they represent in Phase I of oxidation….

A

3A4 (50%) and 2D6 (30%)

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31
Q

What does Phase I of metabolism include

A

oxidation mainly with CYP450 (3A4) to make drug polar, able to be eliminated

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32
Q

Liver Disease=

A

Dose Adjustment!

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33
Q

What is a Loading Dose refer to

A

doubling dose may lead to a “kick start” or earlier onset of action

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34
Q

Define Steady-State

A

situation where drug in=drug out and plasma levels of drug are steady regardless of when sample is taken.

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35
Q

define third spacing and list examples

A

very little fluid exist in this space & it has no function… pleural cavity & peritoneal cavity, and GI tract

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36
Q

how can third-spacing lead to hypovolemia

A

either pt is hemorrhaging or losing fluids into one of the cavities where its not helping the body

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37
Q

What accounts for the decrease in % body water with increasing age

A

adipose tissue

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38
Q

How would you adjust dose for infant with more % body water

A

increase the dose

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39
Q

how would you adjust the dose for an elderly with less % body water

A

decrease the dose

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40
Q

What organs would be considered Phase I of distribution based on CO & Q

A

heart, lungs, liver, kidneys, and brain

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41
Q

what organs are considered Phase II of distribution

A

muscle, skin, adipose tissue

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42
Q

why is the measurement of volume distribution said to be “apparent”

A

its assumed the concentration of drug found in the sample represents all other compartments in body. Rarely true due to protein binding, ion trapping

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43
Q

how is volume of distribution related to drug concentration

A

Inversely

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44
Q

many acidic drugs are highly protein-bound thus would they have a small or large Vd

A

small

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45
Q

what protein are acids most likely to bind to

A

albumin

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46
Q

which type of protein are bases most likely to bind to

A

alpha-1 glycoprotein

also lipoproteins

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47
Q

what is albumin’s main funciton

A

maintain osmotic pressure of blood, transport endogenous substances.

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48
Q

this protein tranports plasma lipids & may bind drugs if albumin is saturated

A

lipoprotein

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49
Q

where are erythrocytes made

A

bone marrow of membranous bones-vertebrae, ribs, sternum

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50
Q

hemolytic anemia caused by penicillin is what type of hypersensitivity rxn

A

Type II, when penicillin binds to RBC, body recognizes as “foreign” launches an IgG attack

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51
Q

what would you see in patients with edema

A

dilute drugs (increase Vd) that are highly water soluble or protein bound

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52
Q

in capillaries what is the primary route of transportation of a drug

A

paracellular,

53
Q

list the relative permeability of capillaries from greatest to least

A

liver>kidney>muscle=fetus>brain

54
Q

what has a more permeable capillary bed between the muscle and the liver

A

the liver

55
Q

list the restricted spaces of the body & why fat soluble drugs moe better across these membranes

A

brain, placenta, and eye; fat soluble move better across these restricted spaces b/c its dependent upon passive diffusion

56
Q

what are examples of protected tissues

A

blood-brain barrier, placental barrier, and blood-retinal barrier

57
Q

What is ion trapping

A

weak acidic drugs trapped in basic environments & vice versa

58
Q

drugs dissolve in water (water soluble drugs) accumulate in which spaces as reservoirs

A

blood & interstitial fluid

59
Q

how are protein-bound drugs reservoirs?

A

they are inactive when bound and as the same free drug is used up, then they are released

60
Q

what type of reservoir can lead to toxicity

A

tissue protein bound drugs b/c they prolong action hence leading to harmful accumulations

61
Q

what are examples of toxicity due to tissue protein bound drugs

A

aminoglycosides (antibiotic class), renal tissue (temporary renal failure), and central auditory tissue (deafness)

62
Q

in the BBB, what cells promote formation & health of the tight junctions making drug penetration dependent on transcellular transport

A

astrocytes

63
Q

what does inflammation do to the BBB which makes it possible to treat meningities with water soluble antibiotics

A

breaks down the barrier, increasing permeability

64
Q
  1. Results of exposure to a toxic metabolite may include
A

cellular and tissue necrosis, anemia and blood dyscrasias, carcinogenesis, mutagenesis, teratogenesis and fetal death

65
Q

phase I of drug clearance involves:

A

oxidation/reduction which doesn’t change water solubility, but alters property of the drug…

66
Q

phase ii involves

A

synthetic rxns, increase polarity & water solubility. increasing drug clearance.. involve conjugation with endogenous substances (glucoronic acid, sulfate, glycine

67
Q

what is the only phase II reaction occurs in the liver

A

glucuronidation

68
Q

where is glucuronides secreted from?

A

the bile

69
Q

what are two other substances that conjugate with amino acids in Phase II that are not secreted in bile

A

glutamine and glycine

70
Q

what is the mechanism for acetaminophen accumulating as a toxic metabolite in the liver

A

it undergoes phase II preferentially (doesn’t require prior phase I oxidation) and if overdosed, overwhelms the phase II- forcing phase I metabolism.

71
Q

rate of metabolism relationship with half life

A

inverse

72
Q

what are factors affect rate of metabolism

A

drugs, liver disease, malaria, neoplastic disease (cancer) Age, nutritional status (protein poor-lower metabolism) vs. high protein diet speeds up) smoking & veggies speeds up. Grapefruit juice increases bioavailibiility by inhibiting intestinal elimination. intestinal microflora

73
Q

factors affect glomerular filtration of a drug

A

MW, diseases,

74
Q

describe enterohepatic recycling or recirculation

A

drugs with more neutral charges (greater lipid solubility) may be reabsorbed from the intestines & re-enter the liver

75
Q

what pH does the urine range

A

4.5-8

76
Q

Urine becomes more acidified in what part of the nephron

A

distal tubules and collecting ducts

77
Q

What could you do to increase the exctretion of weak acids that in a normally acidic urine would be reabsorbed…

A

give them 1 to 2 mEq/kg sodium bicarbonate (alkanize) every 3-4 hrs

78
Q

How could alkanizing the urine of a patient with a cocaine or aspirin overdose help them excrete them faster?

A

normally when the urine is acidic, this promotes the reabsorption of weak acids back to the body thus alkanizing the urine would counteract this process.

79
Q

Where does active tubular reabsorption occur? What molecules is this important for? Unimportant?

A

Proximal tubules, important for endogenous molecules like ions, glucose, amino acids
Minimally important for most drugs

80
Q

Active Tubular Secretion

A

runs against a concentration gradient, many drugs eliminated this way.

81
Q

How will a drugs half-life be affected if it has a lower affinity for the carrier mediated tubular secretion than another drug with a higher affinity

A

The half life will be prolonged

82
Q

in general drugs are excreted with bile when they have already undergone:

A

hepatic metabolism, but some may enter bile unmetabolized

83
Q

drugs & metabolites present in bile are released in the gi tract via:

A

major duodenal papilla

84
Q

what types of drugs does pulmonary excretion work on

A

volatile drugs that are unchanged

85
Q

what are two factors affect drug excretion through breast milk

A

more concentration & less plasma protein binding lead to higher exretion

86
Q

what is meant by the term “dosing to effect”

A

when condtions are present that alter 1/2 life (liver/renal ds) a physiologic marker for effectiveness or toxicity is often used to adjust dosing.

87
Q

why doesn’t half life give you a good picture for full elimination

A

metabolites may be stored in fat cells so although it only takes 2 hours to reach t1/2, it usually takes 5X to assume total elimination

88
Q

in terms of an efficacy half life, how could a drug produce an effect after its eliminated

A

acting intracellularly and/or remains partly bound to the receptor or is a “hit & run” that alters receptor.

89
Q

What does the Cyclooxygenase enzyme do

A

synthesizes prostaglandins from arachidonic acid

90
Q

What role does prostaglandins play

A

pain, inflammation, cell proliferation, mucus production, fever,

91
Q

Which type of COX enzyme would be termed the “housekeeper”

A

COX 1, secretes mucus to protect stomach from gastric juices; clots blood, regulates perfusion to kidneys

92
Q

This COX enzyme is referred to aa inducible

A

COX 2

93
Q

COX 2 plays a role in :

A

inflammation site: increases prostaglandin production(macrophages & synoviocytes)

94
Q

Why is COX 1 referred to as constitutive i.e. what does constitutive mean?

A

It is present at all times; and it has the power to form a part of something

95
Q

HOw might a stomach ulcer form?

A

COX1 inhibitor

96
Q

how can inhibiting COX2 lead to high blood P & increased CV disease risk

A

they are found lining interior of the bv

97
Q

What role does COX2 play int he kidney, which if inhibited would lead to fluid retention

A

regulating water & sodium excretion

98
Q

what is acetaminophen’s thought MOA

A

acts primarily in CNS to inhibit COX2 enzymes hence decreasing pain…. indirectly blocks…. direct effects on hypothalamus’ heat regulating center accounts for antipyretic nature

99
Q

What is acetaminophens indication & dosing

A

it is an analgesic & antipyretic; only analgesic approved to use in infants <6 months. Dose-650-1000mg 4-6 hrs/day

100
Q

What organ is most likely toxic from acetaminophen & why?

A

liver, normally the drug goes through Phase II metabolism here as part of the CYP450, but if it is being all used (overdose) then in can bump into Phase I producing a toxic metabolite that can accumulate in hepatocytes and destroy them.

101
Q

IBuprofin causes the following ADR’s

A

GI (peptic ulcer disease) CV risks (stroke & MI) & kidney (high albumin binding displacing other drugs/blockage of prostaglandins regulate Q)

102
Q

in addition to IBuprofin having antipyretic & analgesic properties similar to acetaminophen, what else does it function to do

A

anti-inflammatory

103
Q

what is Ibuprofin’s MOA

A

it is non-selective on COX1 and COX2

104
Q

why doesn’t acetaminophen have anti-inflammatory effects

A

Since it works in the CNS, it doesn’t inhibit COX in the peripheral tissues

105
Q

What is the onset of acetaminophen

A

30-60 min

106
Q

which drug would you choose to treat osteoarthritis with? It is less potent, and has less ADR’s

A

acetaminophen

107
Q

Why is acetaminophen not as likely as IBuprofin to cause kidney problems

A

It’s protein binding is only 10-25%

108
Q

What is Ibuprofins affinity to Albumin

A

90-99% bound

109
Q

What are the 2 most important things we should know about drugs

A
  1. any drug can cause a symptom 2. any drug can cause an allergic rxn
110
Q

What is the dosing for Ibuprofin

A

200-400 mg every 6 hours

111
Q

Why is using ideal body weight in obese patients wrong for dosing?

A

we would underdose them because adipose tissue blocks the full effect of drugs getting to tissues

112
Q

when using “adjusted body weight” they use a factor around what percent to give a medication for obese

A

40% (rather than using the pt weight)

113
Q

Dose using “total body weight” means:

A

more drug for the patient who weighs more

114
Q

Many carcinogens are only activated after:

A

biotransformation of a reactive metabolite which may cause toxic effects

115
Q

What are some examples of problems caused by toxic metabolites

A

teratogenesis, mutagenesis, carcinogens, blood dyscrasias, tissue necrosis

116
Q

How do anaerobic bacteria contribute to reabsorption in liver (enterohepatic recirculation)

A

they can hydrolyze the conjugated drug

117
Q

The mechanism of extretion through the bile is mainly what type of transport?

A

carrier mediated active; transporters present in canalicular membrane of the hepatocyte

118
Q

What are some examples of semi-polar solvents

A

alcohol & ketones (may act to induce a certain degree of polar/nonpolar)

119
Q

What is cosolvency refer to:

A

a blending of solvents with varying degrees of polarity to create optimal polarity for solute to dissolve in solvent!

120
Q

which form (ionized/unionized) would be favored in a weak acid and weak base at low pH?

A

HA and HB+

121
Q

Would the pH be low or high when a solution is dominated by A- and HB

A

high or basic pH

122
Q

What are some examples of tissue reservoirs

A

bone, GI tract, thyroid

123
Q

How does meningitis make it possible for water-soluble antibiotics to cross the bbb and work to treat it

A

the inflammation breaks it down, makes membrane more permeable

124
Q

how does ion trapping occur in fetal circulation?

A

Since the fetal plasma is more acidic than the mother’s weak bases accumulate across the placenta

125
Q

What is the underlying cause of diabetic retinopathy

A

the blood ocular barrier (consists of tight junctions/nonfenestrated capillaries) becomes leaky due to inflammation & leads to eye damage

126
Q

What is responsible for differences in drug metabolism in patients of varying ethnicities

A

*CYP450 enzyme polymorphism

127
Q

What landmarks begin and end the duodenum

A

pylorus to suspensory ligament(Treitz ligament)

128
Q

what is the mesentery’s main function

A

supplies blood, nerves, and lymph to the SI and GI

129
Q

HOw does the Crypt of Leiberkuhn contribute to health and maintenance of SI

A

consist of undifferentiated cells to replace epithelium

Fundamentals Part 2 (8 decks)

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