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Pharmacology: Exam 1 > Unit 1. Lec 3- Pharmacokinetics III > Flashcards

Unit 1. Lec 3- Pharmacokinetics III Flashcards

1
Q

What is the main phase II reaction?

A

Conjugation (via transferases)

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2
Q

What are the main mechanism of conjugation reactions?

A
  • Coupling of the drug
  • Polar metabolite from phase I rxn uses enzymes known as transferases to an endogenous substrate
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3
Q

List the types (6) of conjugation reactions

A
  1. Sulfatation
  2. Actetylation
  3. Methylation
  4. Glucoronidation
  5. GSH (reduced glutathione)
  6. Amino acids (e.g. glycine)
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4
Q

Mechanism of Glucoronidation

Conjugation rxn

A

Covalent addition of glucaronic acid (e.g. morphine)

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5
Q

Mechanism of Sulfatation

Conjugation rxn

A

Addition of sulfate group (e.g. minoxidil)

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6
Q

Mechanism of Acetylation

Conjugation rxn

A

Addition of acetyl group (e.g. sulfonamide antibotics)

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7
Q

Mechanism of Methylation

Conjugation rxn

A

Addition of Methyl group

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8
Q

Mechanism of GSH (reduced gutathione)

Conjugation rxn

A

Addition of glutathione

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9
Q

Mechanism of amino acids

Conjugation rxn

A

Addition of amino acids (e.g glycine)

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10
Q

Why are most conjugates highly polar?

A
  • It makes them water soluble and unable to cross the plasma membrane
  • Making them almost always pharmacologically inactive and of little or no toxicity
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11
Q

List factors (7) that influence drug metabolism

A
  • Physiologic or disease state
  • Genetic Variation
  • Drug Dosage
  • Age
  • Route of Drug Administration
  • Enzyme Induction
  • Enyzme Inhibition
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12
Q

What can influence a drug’s hepatic clearance?

A

Pathological factors that alter liver function

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13
Q

How can congestive heart failure (inefficient pumping) affect drug metabolism?

A

It can decrease hepatic blood flow and distribution of drugs

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14
Q

What can alter the ratio of bound to unbound drug?

A

Alteration in albumin production

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15
Q

What is the main site of serum-albumin production and drug biotransformation?

A

Liver

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16
Q

Explain how genetic variation can influence drug metabolism.

A
  • There is a great variation in the activity of N-acetyl transferase enzyme among different population.
  • The proportion of drugs metabolized by the major cytochrome P450 enzyme (know about CP450 CYP2D6 is a polymorphic drug-metabolizing enzyme)
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17
Q

If you are a fast acetylator, do you have more or less drug concentration in blood? Do you have more or less tranferase?

A

Less drug [ ], More transferases

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18
Q

If you are a slow acetylator, do you have more or less drug concentration in blood? Do you have more or less tranferase?

A

More drug [ ], less transferases

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19
Q

How does dosage influence drug metabolism?

A
  • As drug dosage increases = drug [ ] may saturate metabolic enzyme
  • If Phase II enzymes are saturated, it gets metabolized by CYP450 enzymes
  • This can lead to an Intermediate that causes Hepatic cell death

ex: high dosage of acetaminophen causing hepatic cell death

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20
Q

How does age influence drug metabolism?

A
  • Young children: (primarily infants) Drugs may be MORE ACTIVE, b/c lack of development of Phase I & II enzymes (No enzymes=NO biotransformation)
  • Older childen: Drugs may be LESS active than in adults if the drug is given based on weight. Liver develops faster than the general increase in body weight
  • Older people: metabolizing enzymes decline
21
Q

How does the route of drug adminstration influence drug metabolism?

A
  • If drug is taken orally the first pass effect influences how the drug is metabolized
  • First pass effect: Combined action of bacterial enzyme within intestine and liver on the drug taken orally.
22
Q

How does enzyme induction influence drug metabolism?

A
  • Increases the synthesis or decreases the degrading of certain drug metabolizing enzymes
    Increases enzyme that breaks drug down

E.g. Cigarette smokers have a polycyclic aromatic hydrocarbon component that induce the N-demethylation (Phase I) pathway

23
Q

What two drugs act as Enzyme Inducers?

A
  • Phenobarbital
  • Rifampin
24
Q

Enzyme induction can produce a condition known as ____

A

Pharmacokinetic Tolerance:drugs can block certain enzymes that are involved in metabolizing other drugs

25
Q

How does enzyme inhibition influence drug metabolism?

A
  • Some drugs can decrease the metabolism (breakdown) of other drugs
  • This inhibition may occur by destruction of drug-metabolizing enzymes, by inhibition of enzyme synthesis

Inhibit enzyme that breaks down anothe drug, therefore increases concentration

26
Q

Example of drugs that benefit from ezyme inhibition

A

Activity of the Phenytoin is increased by co-adminstration of Chloramphenicol

27
Q

List the three processes involved in the excretion of drugs and metabolites in the urine

A
  1. Glomerular Filtration
  2. Active Tubular Secretion
  3. Passive Tubular Reabsorption
28
Q

Explain Glomerular Filtration

A
  • If drug is bound to protein, it will NOT go through glomerular filtration
  • FREE drugs only
29
Q

Explain Active Tubular Secretion

A
  • Fixed capacity: Some drugs can get secreted into the urine, some drugs can get reabsorbed
  • Limited transporters: they can be saturated
30
Q

Explain Passive Tubular Reabsorption

A
  • pH of the urine (pH4-8) determines ionization
  • Un-ionized form of drug can get readily absorbed in systemic circulation
31
Q

What is biliary excetion?

A
  • Enterohepatic recirculation (biliary cycling)- Transport system analagous to those found in kidney actively secrete drugs into bile
  • Transport drug into bile through active transport, then get reabsorbed from GI tract.
32
Q

Biliary excretion favors compounds with molecular weight ____

A

greater than 300

33
Q

Conjugated drugs can be ____ to the free drug by _____ and ____ into circulation

A
  • hydrolyzed
  • intestinal bacteria
  • reabsorbed
34
Q

Enterohepatic recirculation ____ elimination of drugs and ____ duration of action

A
  • reduces
  • prolongs
    keeps drug in body for long time

keeps drug in body for long time

35
Q

Milk is slighty ______ compared to plasma

A

Acidic

36
Q

What type of drug will get stuck in milk?

A

Basic

37
Q

Why is milk important?

A

For mursing infants and as a residue in diary products

38
Q

True or False: Drugs can be excreted from the lungs (pulmonary)?

A

True (anesthetic gases, alcohol)

39
Q

What other things can drugs be excreted from?

A

Sweat, saliva, and hair

40
Q

Define Clinical Pharmacokinetics

A

Is the process of using drug concentration, pharmacokinetics principles, and pharmacodynamics criteria to optimize drug therapy in individual patients

41
Q

Explain Bioavailability and what does it measure

A
  • Bioavailability factor (F) is the percentage or fraction of the dose, which reaches the systemic circulation
  • Parameter that measures drug absorption

E.g. 0.6=60% in systemic circulation

41
Q

Explain Bioavailability and what does it measure

A
  • Bioavailability factor (F) is the percentage or fraction of the dose, which reaches the systemic circulation
  • Parameter that measures drug absorption

E.g. 0.6=60% in systemic circulation

42
Q

IV drug will have a bioavailabilty of _______%?

A

100

43
Q

Expain Apparent Volume of Distribution and what does it measure

A
  • Is the proportionality constant that relates the amount of the drug in the body to the serum concentration
  • Parameter the measure distribution of the drug
44
Q

Apparent volume of distribution

  • Relates…
  • Important for
  • Measured in
A
  • Relates the dose of the drug to the concentration found in plasma
  • Important for Clearing and dosing
  • Measured in L and mL
45
Q

Explain Clearance and Half-life. What does it measure and how is it measured?

A
  • Clearance represents rate of drug removal
  • Half-life is the time it takes for thr concentration of drug in the plasma to decrease by 50%
  • Parameter that mesures Drug Elimination
  • Per unit of time: mL/min, L/hr
46
Q
  1. Which of the following is true regarding enzyme inhibition?
    a. They increase the synthesis of drug metabolizing enzymes
    b. They decrease the degradation of drug metabolizing enzymes
    c. Chloramphenicol is an enzyme inhibitor
    d. They can produce a condition known as tachyphylaxis
A

c. Chloramphenicol is an enzyme inhibitor

47
Q
  1. What type of drugs are more likely to be trapped in milk
    a. Weak Acid
    b. Strong Acid
    c. Weak Base
    d. Strong Base
A

c. Weak base

48
Q
  1. Drugs administered intravenously have a bioavailability of _____:
    a. 0.5
    b. 0.75
    c. 1.0
    d. 0.25
A

c. 1.0

Pharmacology: Exam 1 (9 decks)

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