TDM and Drug Assays

Question 1

What is TDM impacted by?

Answer 1

1. Demograhics factors
2. He;ath rwltaed factors
3. extracorporeal Treamentets
   4.. Personalf factors - ADME

Question 2

Specimane types - Most common

Answer 2

1. venous blood
2. serum
3. Plasma
4. urine - not as commonly used

Question 3

What is phlebpotmy

Answer 3

the drawing of blood from the body

Question 4

what is the common site for blood draws?

Answer 4

mediam cubital vein or any vein in arm

Question 5

Tube types -

What do plasma tubes need?

Answer 5

anticogulants

Question 6

Tube types -

What do serum tubes need?

Answer 6

blood clotting - fibrinogen

Question 7

tube types - what are the top 4?

Answer 7

1. plan tube - serum (red)
2. Plain tube with SST gel - serum (orange)
3. EDTA - anticoagulants - plasma (Pink)
4. Lithium heparin anticoagulant - plasma (green)

Question 8

what is centrifugtaion?

Answer 8

part of specimen processing so specimen separtes based on desnity

Question 9

adtanvage of centirfugation?

Answer 9

these specimens then have np cells and are much cleaner allowing fro photometric analysis

• separator gel

Question 10

what are the four pre analytic factors

Answer 10

1. Drug dpsing accurancy
2. appropreite sampling time
3. handlcing and collection of sample
4. physiological changes in patient

Question 11

what are some specimen clean up or purification mean?

Answer 11

1. centrifugation
2. proetin precipitaion
3. liquid-liquid extraction
4. solid phase extraction
5. chromatogrpahy
6. ultrafiltration

Question 12

measuring free drug level via what tecnique?

Answer 12

immunoassay

Question 13

Free drug or bound drug, active?

Answer 13

free drug

Question 14

what drugs are specically important to monitor free drug levels?

Answer 14

Phenytoin
Valproic acid
Carbamazapine

Question 15

Specimen processing: free drug measurement when and why?
-4 points

Answer 15

1. meausremnt of serum drug concetration may be misleading fro highly;y protein bound drugs
2. under conditions of uremie, liver disease and hypoalbuminemia, free drug levels may be high however the drug levels are in therapeutic range
3. drug -drug interaction may lead to increased free drug levels
4. in elderly they have hypoalbunemic so increased free drug concentration

Question 16

how to measure a freed drug if we have bound drig?

Answer 16

must separte so can use ultrfiltration

must have assay with good analytical sensitivity

Question 17

cons of free-drug measuring (3)

Answer 17

1. more costly and lower accuracy
2. more time and resources (highly sensitive to temp, ph)
3. thought to be similar to Total drug levels as long as free drug levels don’t vary much between people

Question 18

Immunoassay methods vs chromatography method

Answer 18

Immunoassay
- less labor entensive and faster turn around
- limited by lack of spcificay between parent drug and metabolite (potential false positive) and cross-reactivity with similar drugs
- susceptible to interfere by bilirubin and lipedemmia, hemoglobin, paraproetins and heterophiloc antibodies

Chromatogprhy
- liquid chromotpgarhy - tandem mass chemtogaprhy can simultaneously analyse multiple drugs in a single assay
- typically higher specificity for the drug

Question 19

TDM - immunassays, gas chromatogrpahy, and liquid chromatogrphay

Answer 19

Immunoassays
- for over 25 commercial assays

gas chromatography
- flame ionization detection/mass spectrometry

liquid chromatography
- UV/flurescence/mass spec

Question 20

Immunoassays pros and cons

Answer 20

pros
- rapid
- sensitive
- loe cost
- small sample size
- mainly vis plasma or serum

cons
- major concern is antibody specificity

Question 21

Propeties of an antibody- antigen bond

Answer 21

• non-cavalent
• reversible
• intermolecualr focres (hydrongen bonding, ionic bonding, hydrophobic interactions, van der wall forces)
• clonal varaition

Question 22

antigen antibody bonding causes what?

Answer 22

structual changes consistent with indiced fit mec

Question 23

whats provides specificalty to antibody and antigens interactions?

Answer 23

amino acid residues

Question 24

Antobody affinity in equilibrium. process

Answer 24

Ag + Ab reverisble AB X AG

Ka = (ABxAG)/(Ab=Ag)

Question 25

Immunassays use monclonal or polyclonanle antobodies?

Answer 25

both

Question 26

What is a monclonald antibody

Answer 26

population os antibodies that recognize antigen at several epitopes

Question 27

what is a polyclonal antibody

Answer 27

population of antibodies that recognize target antigen at a single epitope

Question 28

where do the labels used in ummunoassay go?

Answer 28

on the analogue of the target or the antibody

Question 29

what kind of labels are there?

Answer 29

Enzymatic or non-enzymatic

Question 30

what kind of immunoassay do we have?

Answer 30

1. competitive - measures small molecules - uses single antibody but competes with labeled analogue of the target compound 2. immunometric - measure larger molecules - uses two antibodies and formed a sandwich with the target ( labeled antibody and captured antibody)

Question 31

what are drug assay commenly?

Answer 31

competive immunoassay

Question 32

describe how a PETINA works

Answer 32

- uses light sacttering to measure drug levls - if bound more tubity - of unbound less turbity

Question 33

features of chromatogrpahy

Answer 33

- less common - used when immunoassay not availble - less rapid - sample requirement variable - serum, plasma and blood

Question 34

why do we sue chromatogrphy?

Answer 34

for separtaion of compounds for MS meaudrmenst

Question 35

different type of chromatogrohay

Answer 35

1. gass chormatogprhy - votalaity of gases 2. liquid chromatography - polarity of substances

Question 36

sensitivity of glass chromatography depends on what?

Answer 36

the detector

Question 37

Big advantage of chromatography

Answer 37

multiplexing

Question 38

Where do therapeutic drug ranges come from?

Answer 38

usually RCTS

Question 39

what are the analytical factors impacting TDM results?

Answer 39

1. method selctivity for target drug vs metabolites 2. method reproducibility 3. avaialibily of pure satdnard reference materials 4. interfering substances in the sample

Question 40

what are common types of error

Answer 40

Systematic error and random error

Question 41

what can systemcatis and random error lead to?

Answer 41

issues in accuracuy

Question 42

trueness refers to

Answer 42

systematic error

Question 43

imprescision referes to

Answer 43

random erro

Question 44

inaccuracy refers to

Answer 44

systematic and random error

Question 45

acidic drugs bind to

Answer 45

albumin

Question 46

basic drugs bind to

Answer 46

alpha 1 - acid glycoproetin

Question 47

when are free drugs levels very imporatn?

Answer 47

when we have altered binding 1. disease 2. drug interaction 3. non-linear binding

Question 48

what to know about blood collection from young children

Answer 48

uses micro-containers and capillary sampling many preanalytics issues - hemolysis - onadequant volume - improper ratio bw blood and anticoagulant

Question 49

collection tube red

Answer 49

no anticoagulant or gel - all drugs including free drugs

Question 50

collection tube green

Answer 50

Heparin (lithium, sodium, ammonium) - lithium Heparin should not be used for a Li meausrment - aminoglycosides not used on heparin plasma if EMIT method

Question 51

collection tube purple

Answer 51

EDTA - preferred for immunoassay (whole blood) - mycophenolic acid (plasma)

Question 52

collection tube yellow/orange

Answer 52

Serum (sst) - unsuitable for certain drugs

Question 53

hemolyisis affect on acetminophen

Answer 53

hemolyis can cause high acteaminophen

Question 54

concers with cross reactivity

Answer 54

especially with competive immunoassay

Question 55

different method yield differnt results

Answer 55

- problem for immunoasssay - less for chromatogrpahy