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Flashcards in Pharmacokinetics Deck (25):
1

volume of distribution =

amount of drug in body/plasma drug concentration

2

low Vd means drug distributes to:

intravascular compartment

3

medium Vd means drug distributes to:

ECF

4

high Vd means drug distributes to:

all tissues (including fat)

5

clearance

- volume of plasma cleared of drug per unit time
- (0.7)(Vd)/(t 1/2)

6

bioavailability

fraction of administered drug reaching systemic circulation unchanged

7

How many half lives does it take for a drug to reach steady state?

4-5 (time to steady state depends ONLY on t 1/2 of the drug)

8

In renal or liver disease, the ______ dose remains unchanged but the ____ dose decreases.

loading, maintenance

9

Zero-order elimination

- rate of elimination is constant regardless of drug concentration
- constant amount of drug eliminated per unit time

10

Key examples of zero-order eliminated drugs:

phenytoin, ethanol, aspirin (PEA in shape of 0!)

11

First-order elimination

- rate of elimination is proportion to drug concentration
- constant fraction of drug eliminated per unit time

12

Only ____ forms of drug can be reabosorbed.

neutral (uncharged)

13

Weak acids get trapped in ____ environments.

basic

14

Weak bases get trapped in ____ environments.

acidic

15

pH > pKa

deprotonated

16

pH < pKa

protonated

17

Phase I metabolism

- reduction, oxidation, hydrolysis via CYP450
- yields slightly polar, water-soluble metabolites that are often still active

18

Phase II metabolism

- conjugation (glucoronidation, acetylation, sulfation)
- yields polar, inactive metabolites
- preserved in geriatrics

19

efficacy

maximal effect a drug can produce (Vmax)

20

potency

amount of drug needed for given effect (more potent = less of it needed) (Km)

21

competitive antagonists change ____ but not ____.

Km, Vmax

22

noncompetitive antagonists change ___ but not ____.

Vmax, Km

23

partial agonists change ____ and changes in ____ are variable depending on mechanism

Vmax, Km

24

therapeutic index

TD50/ED50 --> want it to be VERY large to be a safe drug

25

drugs with low therapeutic index

- theophylline
- quinine
- Li+
- digoxin
- immunoglycosides
- aminoglycosides
- phenytoin
- warfarin
- vancomycin

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