TDM basics

Question 1

Therapeutic Index

Answer 1

Ratio between toxic dose and therapeutic dose (TDM when therapeutic index is narrow)

Question 2

ED50

Answer 2

Dose that is effective for 50% of the population

Question 3

TD50

Answer 3

Dose that is toxic for 50% of the population

Question 4

What drugs require TDM

Answer 4

Narrow therapeutic index, Toxic effects not easily distinguished from symptoms, drug level not related to clinical response (cannot directly observe drug effectiveness), drug compliance

Question 5

Lower limit of range

Answer 5

Minimum effective concentration (MEC), lowest level of drug providing desired effect

Question 6

Higher limit of range

Answer 6

Maximum therapeutic/toxic concentration (MTC), Highest drug level providing desired effect

Question 7

Toxic Range

Answer 7

Drug level in bloodstream where the patient experiences toxic effects, higher limit of therapeutic range exceeded

Question 8

Sub-therapeutic range

Answer 8

Drug level in the bloodstream where the patient does not experience the desired effect, lower limit of therapeutic range has not been reached

Question 9

Peak level

Answer 9

highest level of drug in the bloodstream

Question 10

Trough drug level

Answer 10

lowest level of drug in the bloodstream, occurs immediately before drug is administered

Question 11

Drug Half-life

Answer 11

Amount of time it takes for the concentration of drug in the blood stream by one half life

Question 12

Steady State

Answer 12

When the “in-take” of drug is in the equilibrium with the “out-take” of the drug. Want to be in therapeutic range, takes 5-7 doses. This is when we monitor

Question 13

Absorption Phase

Answer 13

process where drug is absorbed by the body

Question 14

Routes of administer (by prevalence)

Answer 14

Oral (peak 1-2 hrs), IV (peak immediate), IM (peak ~30 min), Rectal (peak 4-5 hrs)

Question 15

Which two routes of administration have no absorption phase

Answer 15

IV and IM

Question 16

Distribution phase

Answer 16

Process where drug us moved out of the blood stream into the interstitial space and targeted cell (affected by volume of distribution and protein binding)

Question 17

VD

Answer 17

Theoretically describes the distribution of the drug between plasma and rest of body tissues, mathematically derived

Question 18

Large VD

Answer 18

Drug readily diffuses into the lipid compartment

Question 19

Small VD

Answer 19

indicates drug readily distributes in total water compartment

Question 20

Protein binding

Answer 20

most drugs are bound to a carrier protein to be transported in the blood stream

Question 21

Free drug

Answer 21

biologically active, and not protein bound

Question 22

Low binding protein level equals

Answer 22

more free drug

Question 23

High binding protein levels equal

Answer 23

less free drug

Question 24

Metabolism phase

Answer 24

Process where the parent drug is biochemically modified, converted to metabolite that may be inactive or active

Question 25

Major site of drug metabolism

Answer 25

liver

Question 26

Enzyme induction

Answer 26

induced enzymes: increases metabolizing activity and decreases half-life

Question 27

Enzyme inhibition

Answer 27

inhibited enzymes: decreases metabolizing activity and increases half-life

Question 28

First pass metabolism

Answer 28

Process where the drug us biotransformed in the liver before entering the bloodstream, oral drugs

Question 29

Elimination phase

Answer 29

Metabolized or parent drug is excreted, usually through the kidneys

Question 30

Kidney disease lowers

Answer 30

excretion rate, increases drug half-life

Question 31

Therapeutic range is reached when

Answer 31

When drug oscillates between peak and trough level

Question 32

Which drugs are highly protein bound? (>80%)

Answer 32

Phenytoin, Carbemazepine, Valproic acid

Question 33

When is analysis of free drug indicated?

Answer 33

When a high amount of drug is protein bound