pharmacokinetics

Question 1

first order kinetics

Answer 1

exponential

rate of elimination or absorption is proportional to the concentration of drug

as the concentration falls the rate of elimination or absorption fall proportionately

k and t1/2 don’t change with drug concentration but the rate does

process is complete after 5 t 1/2 lives

Question 2

t 1/2 = what?

Answer 2

0.693/k

Question 3

zero-order kinetics

examples of drugs that use this …

Answer 3

rate of process is independent of drug concentration
examples–> constant IV infusion or metabolism of alcohol.

becomes saturated and operates at maximal capacity , and can’t go any faster even if drug concentration is increased

the rate is constant

Aspirin
Ethanol
phenytoin

Question 4

mixed order system

Answer 4

at drug concentrations below saturation –> first order

at drug concentrations above saturation–> zero-order

Question 5

Vd= …

Answer 5

loading dose/ plasma concentration of drug

Question 6

loading dose = …

Answer 6

Vd x initial plasma concentration of drug (Co)

can be calculated if the Vd is known and the desired plasma concentration of drug are known

Question 7

if a patient has a high Vd then they have a ….. plasma concentration

Answer 7

low plasma conc.

Question 8

the larger the Vd, the ….. the rate of elimination

Answer 8

slower

Question 9

what is total body clearance

Answer 9

apparent volume of fluid from which drug is totally removed per unit time

Question 10

in the elementary model used for most drugs:

the time of peak concentration is INDEPENDENT of what?

Answer 10

dosage.
that means that we can safely shorten the onset of most drugs by simply increasing the dose.

peak concentration is proportional to dose… double the dose and double the peak concentration

Question 11

elimination after cessation of drug administration is a function of Ke and is essentially complete after…

or accumulation to the plateau state is complete after….

Answer 11

4-5 half lives

Question 12

for a drug that has a low therapeutic index … what is a way to minimize fluctuations

Answer 12

giving a smaller dose at more frequent intervals INSTEAD of giving a larger dose at less frequent intervals

Question 13

what is the effect of varied absorption on repeated doses

Answer 13

blunting of the fluctuations characteristics of intermittent medication

Question 14

what are the effects of varied elimination

Answer 14

concentrations attained during the plateau state increase in proportion to the degree of impaired elimination
dosage schedule must be adjusted accordingly

Question 15

what is bioavailability

Answer 15

the fraction of the dose that is absorbed and reaches systemic circulation as intact active drug

affected by:
-route of administration
-drug solubility
-first pass-effect
degredation of drug in intestine

Question 16

Cl=

Answer 16

Vd x (0.693/t 1/2)

Question 17

Css =

Answer 17

F x maintenance dose rate x t 1/2 / 0.693 x Vd

if you double the maintenance dose–> double Css
if you decrease the elimation 1/2 life by 20% the Css increases by 20%

Question 18

how is clearance related to Css

Answer 18

clearance is inversely proportional to css

so if clearance is 1/3 of what it was previously then Css is 3x higher