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NRS 270: Pharmacology > Module 1: Pharmacokinetics > Flashcards

Module 1: Pharmacokinetics Flashcards

1
Q

Pharmacogenetics

A
  • genetic variations in drug response
  • genes that determine drug metabolism

***Individual Gene Level***

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2
Q

Pharmacogenomics

A
  • look at the whole genome
  • study of how a person’s genetic makeup may determine their drug response

***Whole Genome Level***

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3
Q

High Extraction Ratio

A
  • HIGH: 0.7- 1
  • Intermidiate: 0.3-0.7
  • Low: <0.3
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4
Q

Drug Effect Graph

A
  1. Onset of Effect
  2. Peak Effect
  3. Duration of Action
  4. MEC for adverse response
  5. therapeutic window
  6. MEC for the desired response
  • MEC = minimum effective concentration
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5
Q

Extensive vs. Poor Metabolizers

A
  • Genetic make-up affecting outcomes:
    • can increase or decrease drug metabolism
      • decrease or increase efficacy of drug
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6
Q

AUC

A

(Area under the curve)

  • tells you the total amount of exposure to the drug
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7
Q

Drug Clearance

A
  • the removal of a drug from the body expressed as volume divided by time
    • removal of a drug from a volume of plasma in a given time
  • **Does NOT** indicate amount of drug being used
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8
Q

Cytochrome P450 Enzymes

A
  • Liver Metabolism (CyP450)
  • Major enzymes responsible for drug metabolism to transform lipophilic drugs into water-soluble molecules that can then be filtered by the kidneys
  • some drug substrates inhibit CYP450
  • inducers = increase CYP450 = increased metabolism of the drug = decreased bioavailability
  • inhibitors = decrease CYP450 = decreased metabolism of the drug = increased bioavailability
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9
Q

CYP450 Inhibitors

A

GPACMAN

  • Grapefruit
  • Protease Inhibitors
  • Azole antifungals
  • Cimetidine (antihistamine and antacid; H2 antagonist)
  • Macrolides (except azithromycin)
  • Amiodarone (anti-arrhythmic)
  • Non-DHP CCBs (non-dihydropyridine calcium channel blockers)
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10
Q

CYP450 Inducers

A

PCRABS (induce CYP450 to cut up with its claws the medications that it acts on)

  • Phenytoin (anticonvulsant)
  • Carbamazepine (anticonvulsant)
  • Rifampin (TB drug)
  • Alcohol (chronic)
  • Barbituates
  • St. John’s Wort
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11
Q

MEC

A

Minimum Effective Concentration

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12
Q

How many half-lifes to eliminate a single dose?

A

5 half-lifes = 97% eliminated

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13
Q

Protein Binding

A

drugs will bind to proteins which makes it more challenging to monitor

-clinically relevant in high clearance drugs with narrow therapeutic windows

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14
Q

Modes of Absorption

A
  • Paracellular: between cells
  • Transcellular: across cell bodies
    • passive
      • active transport by carrier
        • drug transporters
        • facilitated
    • endocytosis
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15
Q

Significances of Drug Metabolism

A
  • gets rid of undesirable foreign compounds
  • providing a means for producing active compounds
  • some drugs are given as inactive “prodrugs”, which then convert to active form
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16
Q

Extraction Ratio

A
  • the ability of an organ to remove a drug
  • increased extraction ratio = drug cleared very efficiently by organ
  • Clearance is only high if BOTH blood flow and extraction ratio are high
17
Q

Volume of Distribution

A

How much volume the drug is theoretically being distributed into

  • Vd = amount of drug in the body/ concentration of the drug in blood or plasma
  • drugs with higher Vd = higher concentration in extracellular tissue
  • drugs with lower Vd = high concentration in intravascular space
    • limited drug distribution
  • **does not indicate WHERE the drug is being distributed into**
18
Q

First Order Elimination

A
  • most drugs are eliminated in this way
  • elimination is proportional to amount of drug in body
    • amount of drug in body increases –> increased amount of drug elimination and vice versa
  • **FRACTION** of drug eliminated over time remains constant *fixed percentage from previous number*
    *
19
Q

Zero Order Elimination

A

Drug eliminated in each time interval is constant regardless of amount of drug in body

  • fixed % from original
20
Q

Fraction of Dose Remaining

A

Fraction of Dose Remaining = (1/2)n

n = # of half-lifes

21
Q

Prodrugs

A
  • inactive compounds designed to max the amount of active species at the site of action
  • a biologically inactive compound which can be metabolized in the body to produce an active compound
22
Q

2 Phases of Metabolism

A
  • Phase 1: occurs first
    • usually involve oxidation, reduction, hydrolysis
    • generally loss of pharmacological activity
  • Phase II: Conjugation
    • covalently link function group with endogenous glucuronic acid, sulfate, glutathione, amino acid, or acetate

**Some drugs only undergo Phase II reactions**

23
Q

Pharmacokinetics vs. Pharmacodynamics

A
  • Pharmacokinetics: what the body does to the drug
  • Pharmacodynamics: what the drug does to the body
24
Q

Bioavailability

A

amount of drug available in the body to cause pharmacological effects

25
Q

First Pass Loss/ Effect

A
  • the loss of a drug before getting to the site of action when it first passes through the GI and Liver
  • **Drugs with a much high first pass loss require much larger oral than IV doses to achieve same effects**
26
Q

Most Common Metabolic Reactions

A
  1. oxidations: loss of electron
  2. reduction: gain of electron
  3. hydrolysis: breaking a bond by using H2O
  4. Conjugation:
    1. glucuronidation: adding glucuronic acid to molecule
    2. sulfation: adding sulfate to another molecule
    3. acetylation: adding an acetyl group to another molecule
27
Q

Phenytoin and First Order vs. Zero Order Elimination

A

Normally is first order elimination but at high doses has zero order elimination

  • elimination has reached max capacity and can only eliminate a fixed amount at a time rather than a fixed percentage
  • **anticonvulsant nad antiarhythmic**
28
Q

Clearance Equation

A
  • CL (total)= CL (r) + CL(L) + CL(b) + CL(other)
  • r = renal, L = liver, b = biliary
  • determined by blood flow and extraction ratio
29
Q

Central Compartments

A
  • highly perfused
  • heart
  • liver
  • lungs
  • kidney
  • blood
30
Q

Peripheral Compartments

A
  • lower perfusion
  • Fat tissue (including brain)
  • Muscle Tissue
  • Cerebrospinal Fluid
  • Bone

NRS 270: Pharmacology (14 decks)

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