Drug metabolism

Question 1

Vd

Answer 1

= amount of drug in body/plasma conc (amount of water to dissolve in to get plasma conc, expressed in vol or vol/mass)

Question 2

Clearance

Answer 2

= rate of elimination/plasma conc (ml/min) CONSTANT

Question 3

First order kinetics described by Ct (plasma conc at time t) =

Answer 3

C0e^-kt (plasma conc at t0 x e^-rate constant of elimination)

Question 4

First order - t0.5

Answer 4

=(0.693xVd)/Cl

Question 5

average steady state for oral dosing =

Answer 5

=(DxF)/(TxCl)

D= dose
F= oral bioavailability
T= time between doses
Cl = clearance

Question 6

rate of elimination =

Answer 6

= steady state (Css) x Cl

Question 7

rate of infusion

Answer 7

=Css x Cl

Question 8

Css

Answer 8

rate of infusion = rate of elimination

Question 9

drug –> active metabolites

Answer 9

morphine
diazepam
imipramine

Question 10

drug –> toxic metabolite

Answer 10

paracetemol
halothane
cyclophosphamide

Question 11

prodrug –> drug

Answer 11

prednisolone
clopidogrel
enalapril
azathioprine

Question 12

sublingual

Answer 12

GTN

Question 13

rectal (2)

Answer 13

diazepam

steroid for uc

Question 14

intravenous

Answer 14

thiapentone

Question 15

IM

Answer 15

fluphenazine

morphine

Question 16

SC

Answer 16

insulin

Question 17

inhalation

Answer 17

isofluorane, salbutamol

Question 18

intranasal

Answer 18

beclomethasone

Question 19

epidural

Answer 19

bupivicaine

Question 20

intravaginal

Answer 20

clitrimazole

Question 21

intraarticular

Answer 21

steroids for arthritis

Question 22

entral routes (3)

Answer 22

oral, rectal, sublingual

Question 23

parentral routes (5)

Answer 23

IV, SC, IM, IN, inhalation

Question 24

local routes (3)

Answer 24

epidural, intravaginal, intraarticular

Question 25

poor absorption (bioavailability)

Answer 25

gentamycin

Question 26

breakdown in gut (2) - poor bioavailability

Answer 26

cocaine - MAO

digoxin - Ecoli

Question 27

first pass effect

Answer 27

morphine