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RUSVM Pharmacology > Drug Disposition > Flashcards

Drug Disposition Flashcards

1
Q

What is drug disposition ?

A

Study of the movement of drugs in the body across biological membranes from the time of absorption until elimination

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2
Q

What are the stages of drug disposition?

A

Absorption
Distribution
Biotransformation
Excretion

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3
Q

How can drugs be transported across cell membranes?

A

Passive diffusion
Facilitated diffusion
Active transport
Pinocytosis

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4
Q

What are the two types of passive diffusion?

A

Transmembrane- passive through aqueous protein channels or hydrostatic/osmotic differences across the membrane
Paracellular - intercellular aqueous pores

Bulk flow of water can carry small water soluble substances

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5
Q

What are the 3 factors what will affect simple diffusion?

A

Concentration gradient
Lipid solubility (measured by lipid partition coefficient)
Degree of ionization

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6
Q

The (higher/lower) the lipid solubility of the drug the faster the drug crosses cell membranes

A

Higher

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7
Q

Drugs pass cross biological membranes in their (ionized/nonionized) forms

A

Nonionized -> lipid soluble

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8
Q

What is the rate of diffusion dependent on?

A

Ratio of ionized (I) to nonionized (N)

  • > pH of drug
  • > pka of drug
  • > pH of medium
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9
Q

What is pka of a drug?

A

PH at which a weak electrolyte is 50% ionized and 50% non ionized

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10
Q

_________ drugs are ionized in an alkaline medium

A

Acidic

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11
Q

__________ drugs are ionized in an acidic medium

A

Basic

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12
Q

Henderson hasselbalch equation for a weak acid?

A

Pka = pH + log (N/I)

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13
Q

Hendreson Hasselbalch equation for a weak base?

A

Pka = pH + log (I/N)

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14
Q

The (higher/lower) the pka of a weak acid, the higher is N/I, and the (higher/lower) the pka of a weak base, the higher is N/I

A

Higher; lower

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15
Q

_____________________ compounds such as d-tubocurarine are mostly ionized

A

Quaternary ammonium

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16
Q

What is facilitated diffusion??

A

Carrier-mediated transport that does not need energy

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17
Q

How can facilitated diffusion protect the cell from toxic substances ??

A

Transporters move substance from inside the cell to outside

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18
Q

What is active transport?

A

Drug moved from low to high concentration requiring energy

  • > primary- directly use ATP
  • > secondary- use gradient generated by ATP

Can be saturated, is selective, and competitive inhibition

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19
Q

What is pinocytosis ?

A

Endocytosis were cell engulfs drug molecules dissolved in water

Eg aminoglycoside antibiotics by renal tubular cells

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20
Q

What is drug absorption?

A

Transfer of drug from site of administration to the circulation

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21
Q

What drug factors can affect absorption??

A

Molecular size: smaller=faster
Lipid solubility
Degree of ionization (N/I ratio)
Dissolution of drug in water (oral liquid after than solid)
Concentration at site (dose and concentration): higher=faster

Route of admin: subliguinal and inhalation > intramuscular >subcutaneous > oral

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22
Q

What factors related to the animal can affect drug absorption?

A 
Blood flow 
Absorbing surface area 
Connective tissue 
Species 
Individual
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23
Q

How does blood flow alter absorption?

A

Increased blood flow= increase absorption

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24
Q

How can blood flow be altered

A

Drugs, physiological factors, and disease

Heat/massage increase blood flow

Sympathetic stimulation: increase flow to muscles but decrease to GI and subcutaneous sits

Shock/edema decrease flow

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25
Q

What part of the intestine is the main site of absorption for all drugs given orally

A

Upper small intestine (high surface area)

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26
Q

What factors affect drug absorption from the GI tract

A 
Oral absorption of solid drug dependent on dissolution rate 
Activity of gut
Presence of other substances 
Blood flow 
Species 
Individual

Rate depends on gastric emptying

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27
Q

What is distribution of drugs?

A

Transport of drugs from the plasma to the tissues

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28
Q

What factors can affect distribution of drugs?

A 
Physiochemical properties of the drug 
Concentration gradient 
Plasma protein binding 
Tissue barriers 
Blood flow 
Affinity of drugs to certain tissues
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29
Q

________ drugs mainly to albumin in the plasma

A

Acidic

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30
Q

_______ drugs bind mainly to acid a1-glycoproteins and lipoproteins

A

Basic

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31
Q

What affect does plasma protein binding have on drug distribution

A

Bound form of drug is inactive -prolongs half-life
Cannot be distributed, metabolized, or excreted by globular filtration

Binding is reversible and competitive

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32
Q

The rate of plasma protein binding depends mainly on ____________ of drug

A

Concentration

Competitive binding
Binding can be modified by disease

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33
Q

Alteration of blood flow will have what affect on distribution

A

Altered delivery to drug to tissue

Physiological factors/drug/disease

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34
Q

What components of the blood brain barrier prevent drug entry to the brain?

A

Tight capillary endothelial junctions
Glial cells
CSF flow to venous drainage
Active transport (organic acid/base)

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35
Q

What factors can alter the blood brain barrier?

A 
Age 
Inflammation 
Trauma 
Allergic rxn 
Severe hypotension 
Hypoxia 
High dose of organic solvents (alochol)
High does of heavy metals (lead, mercury)
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36
Q

____________ can be sequestered by calcium in skeletal tissues

A

Tetracycline

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37
Q

What is sequestered/accumulates in kidney tissue

A

Aminoglycoside

38
Q

_______ is trapped in the thyroid gland

A

Iodine

39
Q

Movement of drug fro the tissue to the blood

A

Redistribution of drugs

Eg thiopental vs phenobarbital

40
Q

What is biotransformation

A

Chemical alteration of the drug molecule by the cells of the animal

41
Q

What are the two main results of biotransformation ?

A

Change in physiochemical properties

Change in pharmacological activity

42
Q

Inactive drug-> active metabolite

A

Bioactivation

Eg. Cortisone-> hydrocortisone

43
Q

Nontoxic drug -> toxic metabolite

A

Lethal synthesis

Eg Parathion -> paroxon

44
Q

What is the most important tissue involved in biotransformation

A

Liver

45
Q

What are the phase I types of biotransformation reactions?

A

Oxidation
Reduction
Hydrolysis

46
Q

What is the phase II type biotransformation reaction

A

Conjugation

47
Q

The majority of drug metabolism is by _____________ reaction biotransformation

A

Oxidative

48
Q

Where can oxidation reactions occur?

A 
Microsomal 
Non microsomal ( cytosol and mitochondria)
49
Q

What is an example of an non microsomal oxidation reaction

A

Alcohol and aldehyde dehydrogenase to ethanol and acetaldehyde

50
Q

What enzymes are involved in oxidation reactions ?

A 
Xanthine oxidase (eg xanthine to uric acid)
Tyrosine hydroxylase (eg tyrosine to dopa)
Monoamine oxidase (eg catecholamines and serotonin metabolism)
51
Q

What type of reaction adds hydrogen groups? Where can these reactions occur?

A

Reduction

Microsomal and non-microsomal

52
Q

What type of reaction requires water

A

Hydrolysis

53
Q

What enzymes are involved in hydrolysis?

A

Hydrolases

Eg
Esterase
Amidases
Peptidases

54
Q

What is the combination of a drug or metabolite with an endogenous substance

A

Conjugation

55
Q

What is the most common conjugation reaction

A

Conjugation to glucuronic acid

56
Q

What is the only microsomal conjugation reaction

A

Glucronidation (glucuronic acid)

All others are non- microsomal (sulfuric acid, acetyl groups, methyl group, glycine, methionine, and glutathione)

57
Q

Conjugation is deficient in the ____________

A

Neonate

58
Q

Conjugation of __________ to _______________ leads to hepatotoxic products

A

Acyl glucroonic acid to NSAID

59
Q

What are factors that alter biotransformation? (Long list)

A 
Species 
Individual 
Route of admin 
Enzyme inducers/inhibitors 
Liver disease 
Hepatic blood flow 
Plasma protein binding 
Distribution and storage 
Age 
Sex 
Diet and nutrition 
Body temp 
Environmental factors
60
Q

What species are deficient in glucuronyl transfereases and are unable to conjugate phenols and aromatic amines?

A

Cats

61
Q

What species are deficient in hydroxylation and dealkylation?

A

Cats

62
Q

What species lacks acetylating enzymes?

A

Dog

63
Q

What species has less plasma pesudocholinesterases?

A

Ruminants

64
Q

What species have hight levels of oxidative enzymes ?

A

Ruminant and horses

65
Q

What species are deficient in methylases

A

Equine

66
Q

What species are deficient in sulfate conjugating enzymes?

A

Pigs

67
Q

What species lack oxidative enzymes?

A

Birds

68
Q

What species have low levels of drug metabolizing enzymes?

A

Fish

69
Q

How can route of administration alter drug biotransformation ?

A

First pass effect for oral, rectal, intraperitoneal routes, and skin

Drug goes through liver and is metabolized before it is distributed
Eg. Lidocaine, propranolol, and morphine

70
Q

What are drugs that stimulate production of more metabolic enzymes in the liver? Where are they found?

A

Enzyme inducers

Microsomal enzymes

71
Q

What are drugs that inhibit the liver to produce metabolic enzymes??

A

Enzyme inhibitors

72
Q

What are examples of enzyme inhibitors?

A

Chloramphenicol
Cimetidine
Ketoconazole

73
Q

How does biotransformation in newborns and geriatrics compare to adults?

A

Less in newborns and geriatrics

74
Q

Diet and nutrition can alter biotransformation. ______________ foods can induce enzymes and ___________ can be an enzyme inhibitor

A

Charcoal broiled foods

Grapefruit juice

75
Q

Removal of clearance of drug from the body??

A

Drug excretion

76
Q

What are the routes of drug excretion? (Another long list)

A 
Renal 
Hepatic
Feces
Milk 
Semen 
Saliva 
Eggs 
Hair 
Feathers
Sweat glands 
Expired air
77
Q

3 ways drugs are excreted in the kidney?

A

Glomerular filtration
Active tubular secretion
Tubular reabsorption

78
Q

What factors affect glomular filtration

A

Glomular filtration rate- arterial BP -> hydrostatic pressure

Molecular size- less than 7000Da is freely filtered; 7000-70,000Da filtered at a rate proportional to molecular mass

Molecular charge- large negative molecules are not filtered

Plasma protein binding- only unbound are filtered

79
Q

Where does active tubular secretion take place? And what provides the energy?

A

Proximal convoluted tubule
Sodium pump ->. ATPase
Secondary/tertiary active transport (concentration dependent)

(Organic anion and organic cation system)

80
Q

Organic cation transporters carry organic _________

A

Bases/basic drugs

-cimetidine, procaniamide, or nictotine

81
Q

Organic anion transporters transport organic ________

A

Acids/acidic drugs

Eg penicillin, thiazide diuretics, or loop diuretics

82
Q

Where does passive tubular reabsorption occur in the kidney?

A

Proximal and distal convoluted tubules (non-ionized forms of weak acids and bases)

83
Q

What are factors that can affect tubulular reabsorption of drugs?

A

Physiochemical drug properties (soluble/ionized/polar)

Degree of ionization (acidification/ alkalinization of urine pH)

Rate of glomular filtration

Active tubular reabsorption

84
Q

__________________ of the urine pH enhances renal excretion of weak basic drugs

A

Acidification

Ammonium chloride or methionine

85
Q

____________________ of the urine pH enhances renal excretion of weak acidic drugs

A

Alkalinization

Sodium bicarbonate

86
Q

What is the second most important organ for drug excretion??

A

Liver (bile or blood)

87
Q

How can drugs be excreted in bile ?

A

Molecular weight greater than 300Da and presence of a polar group increase biliary absorption

Can be unchanged to as glucuronides

Acid/basic/neutral

88
Q

What are examples of drugs that are significantly excreted in bile?

A 
Steroid hormones
Erythromycin 
Nafcillin 
Digitoxin
Glucuronides of chloramphenicol and morphine
89
Q

What is enterohepatic circulation?

A

Conjugated of lipophillic drugs are excreted in bile -> hydrolyzed in the intestine -> lipid soluble drug is reabsorbed

=> prolonged half life of the drugs

90
Q

What types of drugs are excreted in the feces?

A

Orally administered; non absorbed
Drugs excreted in bile and not reabsorbed
Drugs from plasma to GI tract by passive diffusion

91
Q

(Acid/basic) drugs are excreted in milk in large amounts because of ion trapping. What is the significance of drugs in the milk?

A

Basic

Drug residues
Systemic treatment of mastitis
Adverse effects on newborn

92
Q

Volatile compound like inhalation anesthetic are excreted in ?

A

Expired air

RUSVM Pharmacology (18 decks)

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