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Term III: Pharmacology > Drug Metabolism > Flashcards

Flashcards in Drug Metabolism Deck (26)
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1
Q

Define metabolism.

A

Disappearance of a drug by chemically changing it into another cmpd called a metabolite.

2
Q

Define xenobiotics.

A

Foreign substances that are absorbed or ingested.

3
Q

Define pro-drug. What are its 3 purposes?

A

Cmpd w/ little or no activity that is metabolized to an active species in order to 1) promote absorption, 2) prevent acid destruction, 3) minimize exposure toxicity

4
Q

Define biological half-life.

A

that period of time in which half of the amount of a drug disappears; a function of its rate of metabolism and its rate of excretion

5
Q

Define first-pass effect. What organ is usually involved?

A

occurs when more than half of the amount of a drug is metabolized on its 1st pass through an organ (usually the liver)

6
Q

Almost all drugs are metabolized to compounds that are: (name 3)

A
  1. more polar than the parent compound
  2. not as well reabsorbed and therefore more efficiently excreted
  3. many will become inactive or less active than their parent compound
7
Q

What are the three possible outcomes of hepatic metabolism of pharmacologic cmpds?

A
  1. Activation
  2. Degradation into active or inactive metabolites
  3. Degradation to a toxic metabolite, including carcinogens
8
Q

What is the most important organ for elimination of drugs and their metabolites?

A

Kidney

9
Q

What are the three processes involved in the excretion of drugs and metabolites in the urine? Which is affected most by drug metabolism? Why?

A
  • glomerular filtration
  • active tubular secretion
  • passive tubular reabsorption

Passive tubular reabsorption - b/c metabolite is more polar than the drug that was administered

10
Q

What is the major diff between Phase I and Phase II rxns?

A

Phase II needs a donor molecule, Phase I reactions act on the drug alone

11
Q

Where do enzymes that participate in hydrolysis act?

A

Plasma & cytoplasm

12
Q

What are the reaction classes of Phase I and Phase II?

A

Phase I - oxidation, reduction, hydrolysis

Phase II - conjugation

13
Q

What order are the kinetics of drug metabolism reactions at therapeutic doses?

A

First order

14
Q

What order are the kinetics of drug metabolism reactions at saturation?

A

Zero order

15
Q

What organ has the highest level of drug-metabolizing activity?

A

Liver

16
Q

What system can oxidize drugs? What are its two requirements?

A

Monooxygenase or cytochrome P450 system

  1. Reduced NADPH
  2. Oxygen
17
Q

What drug was removed from the market due to a P450-based toxicity? What condition did it make them susceptible to?

A

Seldane

Cardiac arrhythmias

18
Q

What chemical group is inserted in oxidation?

A

Hydroxyl group

19
Q

What is removed in reduction?

A

Oxygen

20
Q

What does hydrolysis involve?

A

Cleavage w/ addition of water

21
Q

What reaction type frequently uses transferase enzymes? Phase I or II?

A

Phase II

22
Q

What are 4 factors in neonates that makes their drug metabolism capabilities different than adults?

A
  1. Absorption - gastric pH varies
  2. Distribution - body water is greater
  3. Metabolism - p450 is developed, but functions slower; glucuronidation is immature
  4. Excretion - renal blood flow, GFR, tubular function are reduced
23
Q

What are 5 factors in elderly that make their drug metabolism capabilities different than adults?

A
  1. Absorption - may be less efficient
  2. Distribution - can be altered by hypoalbuminemia, changes in drug-binding sites, changes in protein/fat mass ratio
  3. Metabolism - reduced hepatic mass, enzyme activity, and blood flow to liver
  4. Excretion - reduced renal blood flow
  5. Receptor sensitivity - reduced
24
Q

What are the acute and chronic effects of ethyl alcohol on drug metabolism?

A

Acute - inhibits drug metabolism

Chronic - induces hepatic drug metabolizing activity (drugs are not effective)

25
Q

How does grapefruit juice affect drug metabolism?

A

Flavinoids inhibit metabolism of Ca2+ channel blockers and caffeine by inhibiting CYP3A

26
Q

Which of the following drugs will cause an increased metabolism of combination pill oral contraceptives?

A. ampicillin
B. ciprofloxacin
C. erythromycin
D. tetracycline

A

A and D