Chapter 2: Pharmacology

Question 1

equation for volume of distribution

Answer 1

Vd = total in body/ [drug in plasma]

Question 2

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

Answer 2

low Vd- in plamsa

high Vd- all tissues

Question 3

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?

Answer 3

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

Question 4

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

Answer 4

No; it is only goodd for low Vd

Question 5

Interpret a drug’s clearance being GFR

Answer 5

less than gfr– being reabsorbed in distal tubule

> gfr– being secreted actively

Question 6

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?

Answer 6

2 half lives: 6 hours

Question 7

Loading dose or Maintenance dose? Must know clearance to calculate

Answer 7

MD. (key distinction)

Question 8

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

Answer 8

LD (key distinction)

Question 9

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

Answer 9

LD

Question 10

Loading dose or Maintenance dose? Most useful in emergency situations

Answer 10

LD

Question 11

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

Answer 11

MD

Question 12

Identify 3 drugs whose elimination represents a constant amount over time

Answer 12

Phenytoin
Ethanol
Aspirin at very high doses

This is zero-order kinetics

Question 13

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

Answer 13

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)

Question 14

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?

Answer 14

At 7.4 it will be ionized and not cross the membrane

At 2 it will be nonionized and will cross the membrane

Question 15

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?

Answer 15

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

Question 16

What type of metabolism? reduced activity in neonates

Answer 16

glucoronidation

Question 17

What type of metabolism? cytochrome p-450 metabolism

Answer 17

oxidation (phase I)

Question 18

What type of metabolism? genotypic variation may cause SLE

Answer 18

acetylation

Question 19

What type of metabolism? metabolism of chloramphenicol

Answer 19

glucoronidation

Question 20

What type of metabolism? Metabolism of hydralazine

Answer 20

acetylation

Question 21

P-450 inducer or inhibitor? phenytoin

Answer 21

inducer

Question 22

P-450 inducer or inhibitor? erythromycin

Answer 22

inhibitor

Question 23

P-450 inducer or inhibitor? grapefruit juice

Answer 23

inhibitor

Question 24

P-450 inducer or inhibitor? phenobarbital

Answer 24

inducer

Question 25

P-450 inducer or inhibitor? cimetidine

Answer 25

inhibitor

Question 26

P-450 inducer or inhibitor? ritonavir

Answer 26

inhibitor

Question 27

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

Answer 27

decrease potency

no effect on efficacy

Question 28

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

Answer 28

no effect on potency

decreases efficacy

Question 29

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

Answer 29

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