Pharmacokinetics

Question 1

What is the “theoretical” volume necessary to account for the total amount of drug in the body in the same concentration as in the plasma?

Answer 1

Volume of distribution

Question 2

What is the “theoretical” volume of plasma that is completely cleared (100%) of drug in a given period of time?

Answer 2

Clearance

Question 3

What is elimination half-time (T1/2B)?

Answer 3

The time it takes for PLASMA CONCENTRATION of a drug to fall by one-half.

Question 4

What is elimination half-life?

Answer 4

The time it takes for the total amount of drug IN THE BODY to decrease by one-half

Question 5

How is the volume of distribution calculated?

Answer 5

by dividing the amount of drug injected by the plasma concentration; Vd= Q/C, where C is the plasma concentration

Question 6

What drugs in anesthesia have relatively small volumes of distribution?

Answer 6

water soluble

ex) muscle relaxants (ionized and restricted to extracellular space)

Question 7

What drugs in anesthesia have relatively large volumes of distribution?

Answer 7

fat soluble

ex) induction agents (readily dissolves in adipose tissue), opioids

Question 8

What is pharmacokinetics?

Answer 8

What the body does to drugs

Question 9

What is different about a neonate or infants body composition compared to an adult?

Answer 9

they have an expanded extracellular fluid volume (plasma volume plus interstitial fluid volume)

Question 10

How does distribution of muscle relaxants differ in the neonate than the adult?

Answer 10

muscle relaxants are ionized and restricted to the extracellular space–> they have VoD that are greater in the neonate because the neonate has a greater extracellular fluid volume on a weight/kg basis

SUX increase–> immature junctions, more water
NDMB–> give same, immature needs less inhibition; this cancels the more H2O out

Question 11

Give 2 reasons neonates require more sux? For how long?

Answer 11

1) > VOD
2) immature junctions
* extracellular fluid volume is twice that of the adult (40% vs 20%) up to ~ 18 months old

Question 12

What is zero order kinetics?

Answer 12

a constant amount of drug is eliminated per unit of time
ex) 2mg per min
straight decreasing line graph (linear trend with negative slope)

Question 13

What are 3 primary drugs that exhibit zero order kinetics at therapeutic concentrations?

Answer 13

1) alcohol
2) dilantin (phenytoin)
3) aspirin
“ADA ZERO”

Question 14

Most drugs are eliminated by _____ order kinetics.

Answer 14

first

Question 15

What is first order kinetics?

Answer 15

a constant fraction of drug is eliminated per unit of time

Question 16

A constant amount over time=

Answer 16

zero order

Question 17

A constant fraction over time=

Answer 17

first order

Question 18

What is the look of the line graph for first order one compartment?

Answer 18

linear trend with negative slope… but there will be a LOGARITHM (LOOK FOR THIS)

Question 19

What is the look of the line graph for first order two compartment?

Answer 19

Has a distribution or alpha phase (small curve) and an elimination or beta phase (linear trend with negative slope)

Question 20

Name a drug that is eliminated by first order one compartment kinetics.

Answer 20

albumin

Question 21

Where is volume of distribution calculated from on a first order two compartment kinetic model?

Answer 21

from the equilibrium point (between the alpha and beta phase)

Question 22

Drugs will be eliminated rapidly if: (2)

Answer 22

1) their clearances are high
and/or
2) their volumes of distribution are small

Question 23

How many half-times does it take to eliminate 98% of a drug?

Answer 23

6

Question 24

Name the 4 types of phase I reactions.

Answer 24

1) oxidation
2) reduction
3) methylation
4) hydrolysis
“HORM”
*phase I reactions involve chemical biotransformation of a molecule, usually to a more water soluble and often inactive metabolites

Question 25

Name 4 types of phase II reactions.

Answer 25

1) glucuronidation
2) glutathione conjugation
3) sulfation
4) acetylation

Question 26

Phase II reactions involve ______ of a drug or its metabolite with endogenous molecules.

Answer 26

conjugation

Question 27

Acetylation (a phase II reaction) is an important pathway for metabolism of agents such as __________, __________, and _________.

Answer 27

procainamide, hydralazine, isoniazid

Question 28

Phase III reactions are elimination that involve ____________ transport proteins.

Answer 28

ATP-binding cassette (ABC) trasport proteins

Question 29

What is the most abundant plasma protein, therefore binding the majority of injected drugs?

Answer 29

albumin

Question 30

_______ drugs do not leave circulation, only the _____ drugs diffuses across capillary walls to target cells.

Answer 30

protein bound drugs

free (unbound)

Question 31

Only ______ and _______ drug crosses the placental and BB barriers.

Answer 31

free (unbound) and nonionized

Question 32

How does hypoproteinemia (hypoalbuminemia) affect injected drugs?

Answer 32

patients with hypoalbuminemia are more sensitive to injected drugs because protein binding is reduced; more of the injected drug are in the free form.

Question 33

How does hypoproteinemia (hypoalbuminemia) affect the volume of distribution of injected drugs?

Answer 33

increases VoD