Chapter 2: Pharmacology Flashcards Preview

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Flashcards in Chapter 2: Pharmacology Deck (29)
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1
Q

equation for volume of distribution

A

Vd = total in body/ [drug in plasma]

2
Q

Drugs with low Vd are found where, vs. with high Vd?

A

low Vd- in plamsa

high Vd- all tissues

3
Q

A new drug is found experimentally to have an apparent Vd of 2000 L in a 70-kg adult. What is your interpretation of these data?

A

High Vd means it is sequestered in the tissues to great extent

4
Q

Would hemodialysis be an effective way to eliminate a drug with high Vd?

A

No; it is only goodd for low Vd

5
Q

Interpret a drug’s clearance being GFR

A

less than gfr– being reabsorbed in distal tubule

> gfr– being secreted actively

6
Q

For a drug with a t 1/2 of 3 hours given by constant IV infusion, how long will it take for this drug to reach 75% of steady state?

A

2 half lives: 6 hours

7
Q

Loading dose or Maintenance dose? Must know clearance to calculate

A

MD. (key distinction)

8
Q

Loading dose or Maintenance dose? Must know volume of distribution to calculate

A

LD (key distinction)

9
Q

Loading dose or Maintenance dose? Usually administered in a single bolus

A

LD

10
Q

Loading dose or Maintenance dose? Most useful in emergency situations

A

LD

11
Q

Loading dose or Maintenance dose? Given to achieve steady-state plasma levels over time

A

MD

12
Q

Identify 3 drugs whose elimination represents a constant amount over time

A

Phenytoin
Ethanol
Aspirin at very high doses

This is zero-order kinetics

13
Q

Weak acids and bases and their dissociation. What crosses the membrane and what is better cleared?

A

Acid: R-COOH crosses the membrane, R-COOH- and H+ better cleared

Base: RNH3+ is better cleared, RNH2 + H+ crosses the membrane

(polar one is water soluble)

14
Q

Drug #1 is a weak acid with PKa of 4. When placed at pH of 7.4 or pH of 2, will it be mostly ionized or non ionized? Will it cross the membrane easily or not?

A

At 7.4 it will be ionized and not cross the membrane

At 2 it will be nonionized and will cross the membrane

15
Q

Drug #2 is a weak base with a PKa of 8. When placed at a pH of 7.4 or pH of 9, will it be mostly ionized or non ionized? Will it cross the membrane easily or not?

A

At pH of 7.4 it would be ionized and not easily cross membranes

At pH of 9 it would be nonionized and would cross membranes

16
Q

What type of metabolism? reduced activity in neonates

A

glucoronidation

17
Q

What type of metabolism? cytochrome p-450 metabolism

A

oxidation (phase I)

18
Q

What type of metabolism? genotypic variation may cause SLE

A

acetylation

19
Q

What type of metabolism? metabolism of chloramphenicol

A

glucoronidation

20
Q

What type of metabolism? Metabolism of hydralazine

A

acetylation

21
Q

P-450 inducer or inhibitor? phenytoin

A

inducer

22
Q

P-450 inducer or inhibitor? erythromycin

A

inhibitor

23
Q

P-450 inducer or inhibitor? grapefruit juice

A

inhibitor

24
Q

P-450 inducer or inhibitor? phenobarbital

A

inducer

25
Q

P-450 inducer or inhibitor? cimetidine

A

inhibitor

26
Q

P-450 inducer or inhibitor? ritonavir

A

inhibitor

27
Q

When given to a patient already receiving a full agonist, what effect will a competitive antagonist have on potency and efficacy?

A

decrease potency

no effect on efficacy

28
Q

When given to a patient already receiving a full agonist, what effect will a noncompetitive antagonist have on potency and effficacy?

A

no effect on potency

decreases efficacy

29
Q

Therapeutic index. Do we want it to be high or low?

A

The most dangerous drugs have a lower TI (digoxin, warfarin, etc.), whereas safer drugs have a higher TI.