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Pharmacology Exam 1 > Drug metabolism and excretion > Flashcards

Drug metabolism and excretion Flashcards

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1
Q

Biotransformation reactions are often subdivided into these two types

A

Non synthetic
Synthetic

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2
Q

Examples of non synthetic rxns

A

oxidation
reduction
hydrolysis
phase 1
addition or uncovering of COOH, NH2, O, OH, and/or SH

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3
Q

Examples of synthetic rxns

A

conjugation
phase 2
addition of group from endogenous cofactor

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4
Q

Where does biotransformation occur

A

multiple organs; liver is most important

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5
Q

Insertion of oxygen into drug or side product

A

Phase 1 oxidation rxns

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6
Q

Phase 1 oxidation rxns are catalyzed by

A

enzyme system with several names:
cytochrome P450 microsomal system (!!!!)
monooxygenase system
mixed function oxidase system

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7
Q

System in phase 1 oxidation rxns that rarely produces reactive metabolites

A

flavine monooxygenase

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8
Q

Components of P450 system

A

smooth ER
cytochrome P450
NADPH cytochrome P450 reductase
molecular oxygen
NADPH

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9
Q

Families from cytochrome P450 and function

A

CYP1
CYP2
CYP3
responsible for most drug oxidation

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10
Q

Important for many clinical drugs

A

CYP2C
CYP2D

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11
Q

Found in GI tract and is important for first pass effect

A

CYP3A4 (largest group)

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12
Q

Non-P450 oxidation rxns

A

Alcohol and aldehyde oxidation (dehydrogenases)
Purine oxidation (xanthine oxidases)
Monoamine oxidation (oxidases: type A and B, inhibitors used as antidepressants)

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13
Q

Other metabolic reactions

A

Azoreduction
Nitroreduction (chlorampheniol)
Ester hydrolysis (procaine and succinylcholine)
Amide hydrolysis (procainamide and lidocaine)

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14
Q

Type of conjugations phase 2 (conjugation) rxns

A

glucuronidation (most common)
acetylation
glutathione (important for avoiding drug toxicity)
glycine
sulfation
methylation

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15
Q

Endogenous reactant and enzyme for glucuronidation

A

uridine diphosphate glucuronic acid; UDP-glucuronyl transferase

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16
Q

Endogenous reactant and enzyme for acetylation

A

acetyl-coenzyme A; N-acetyltransferase

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17
Q

Endogenous reactant and enzyme for glutathione

A

glutathione; GSH-S-transferase

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18
Q

Endogenous reactant and enzyme for glycine

A

glycine; acyl-CoA glycine transferase

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19
Q

Endogenous reactant and enzyme for sulfation

A

phosphoadenosyl phosphosulfate (PAPS); sulfotransferase

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20
Q

Endogenous reactant and enzyme for methylation

A

S-adenosylmethionine; methyltransferases

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21
Q

Factors affecting drug metabolism

A

plasma binding protein
localization/sequestration of drug in tissues
liver disease
drug-drug interactions

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22
Q

Examples of drug-drug interactions

A

inhibition of drug metabolism
cimetidine
azole antifungals (ketoconazole, macrolide antibiotics, erythromycin)

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23
Q

Induction of drug metabolism

A

increase in cytochrome P450 proteins
barbiturates (broad)
environmental carcinogens (selective)
chronic alcohol (induces CYP2E1)

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24
Q

Misc. factors affecting drug metabolism

A

age
diet
disease
other drugs
environmental chemicals

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25
Is formation of toxic metabolites common?
Yes
26
Toxic metabolites form
electrophilic intermediates that bind to cellular macromolecules
27
Toxic metabolites cause
necrosis mutagenesis carcinogenesis
28
First defense against toxic metabolites
glutathione conjugation (acetaminophen, acetyl cysteine)
29
Principal excretion routes
renal biliary pulmonary sweat saliva tears milk
30
Routes of renal excretion
glomerular filtration active tubular secretion passive reabsorption (back diffusion) active tubular reabsorption
31
Glomerular filtration occurs at
the glomerular capillaries, high capacity! (180L/day; 20% of plasma)
32
Requirements for drug filtration
not too large not bound to plasma proteins lipid solubility or environmental pH do NOT effect
33
Active tubular secretion through
organic anion transporters and peptides (OATs and OATPs) organic cation transporters (OCTs)
34
Active tubular secretion is not completely developed in
newborns
35
Is active tubular secretion specific?
no
36
Is active tubular secretion saturable?
yes
37
How can the inhibition of drugs such as probenecid effect the renal excretion of weak acids (penicillin)
depress the renal excretion
38
Active tubular reabsorption is similar to
active tubular secretion
39
Why is active tubular reabsorption important
to conserve compounds such as uric acid
40
What inhibits active tubular reabsorption
uricosuric drugs (probenicid and sulfinpyrazone)
41
Passive reabsorption requires what form of drug
non-ionized
42
Extent of drug ionization is dependent on
pKa and urinary pH
43
Urinary pH varies between
5-8; can be manipulated by drugs to increase excretion of acids or bases
44
When and where does biliary excretion occur
follows phase 2 conjugation in liver
45
How does biliary excretion occur
through multiple carrier-mediated transport processes
46
Biliary excretion requires and is
energy; saturable and non-specific
47
Enterohepatic cycling can occur during
biliary excretion
48
Liver disease impairs
biliary excretion
49
Biliary excretion is incompletely developed in
newborns
50
What drugs can babys not have due to lack of biliary excretion
sulfonamide- induced kernicterus chloramphenicol- induced gray baby syndrome can cause hyperbilirubinemia
51
Pulmonary excretion is important for
gases and volatiles
52
Pulmonary excretion occurs through
simplified diffusion into expired air
53
Elimination rate of pulmonary excretion is dependent on
respiration rate pulmonary blood flow solubility of drug in the blood: poorly soluble is more rapidly excreted, nitrous oxide > alcohol
54
Excretion via misc fluids
sweat (dermatitis) saliva (drug taste) milk (nursing infants and dairy farming)
55
Phenobarbital is a
weak acid
56
Ionized form of phenobarbital is
excreted
57
Alkaline urine increases fraction in what form how does this effect excretion and reabsorption
ionized; increases excretion and reduces reabsorption
58
How to increase excretion of amphetamine
acidify urine
59
How to increase excretion of phenobarbital
alkalinize urine
60
Amphetamine is a
weak base
61
What form of amphetamine is excreted
ionized
62
Acidic urine increases fraction in what form how does this effect excretion and reabsorption
ionized; increases excretion and reduces reabsorption

Pharmacology Exam 1 (5 decks)

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