Immunoassay and tox

Question 1

How does ouchterolny measure amount of analyte?

Plasma electrophoresis can have what “erronious” band mimicking an M-spike?

Answer 1

Diffuses and ppts and forms a circle

Fibrinogen

Question 2

To be positive in Western blot for HIV you need?

2 tests to measure small concentratons?

Answer 2

TWO positive antibodies in two regions (GP160/120 and/ro p41 and p24)

Competative radioimmunoassay (kit has labled antigen) and non-competitive immunometric (2 antibodies that bind at 2 different locatons with one on solid state) assay

Question 3

What will bioten excess in a patient cause for TSH?

Non-competitive assay’s need what size antigen?

Vs Competitive assays are the upper and lower limits of detection better?

Answer 3

Decreased TSH measurements dure to less captured protein and causes low TSH

Large; and yes ULL and LLD are better

Question 4

What thereaputic index needs monitoring (wide or narrow)?

Which cytochrome affect warfarin metabolism?

What affects pharmacokinetics?

Answer 4

Narrow!

CYP2C19

Drug absorption, distribution, binding, elemination

Question 5

Coccain metabolite tested for in urine?

Pharmacodynamics measures drug interaction where?

What is bioavailability (f)’s formula?

Answer 5

Benzoylecgonine

Tissue sites (aka what drug does to patients)

f= (AUC oral)/(AUC IV); curves are concentration over time

Question 6

What is the distribution phase?

Volume of distribution calculation?

Answer 6

Time for drug to equlibrate with tissue; if levels drawn before then concentration is falsely high

Vd= Dose/ (C- Cnaught); C naught is drug concentration before dose

Vd is high for fat soluble drugs

Question 7

Clerance of drugs:
Zeroth vs 1st?

1st calculation?

Half life calc?

Answer 7

0th: Constant and independent of drug concentration; constant amount removed; eg ethanol and phenytoin; linear
1st: variable and dependent on drug concentration: constant proportion removed

C_t=C_o=e^-kt

t_1/2= 0.693/k

Question 8

How many half-lives to get to steady state?

Equation to clear drug?

Answer 8

5

~5t_1/2 s

Question 9

Digoxin fast or slow equilibraton?

What issues in patients raise measured digoxin?

Tx for toxicity?

Answer 9

Slow so early measurements can be falsely high

Renal failure, shock, PreE, neonates

Digibind by Fab Ab

Question 10

Phenytoin 1st or 0th order kinetics?

What is fosphenytoin?

Is it protein bound?

Answer 10

0th!; small dosage changes lead to huge [] changes

IV drug that can have reactivity as phenytoin in assays

Yes; increased free fraction with low albumin, renal failure, or displacement

Question 11

Poison vs toxin?

Answer 11

Poison is any substance that is injurious to health or dangerous to life; toxin is a biologic poison

Question 12

Antidoes of?
Iorn, Al?

Pb, Hg

Ehtylene glycol?
Nitrites,nitrates?

Answer 12

Fe, Al: Desferroximine

Pb, Hg: Other chelating

Ethylene glycole: Ethanol, fomepizole

Nitrites: Methylene blue (methemoglobinemia)

Question 13

More antidotes of?

Acetaminophen?
Dixogin?
INH?
Opiates?

Organophosphates?

Answer 13

N-acetylcysteine

Digibind

Pyridoxine

Naloxone

Organophosphates: Atropine

Question 14

Expected Osmolality eq?

Answer 14

2x Na + (Glucose/18) + (BUN/2.8) > 10 means significant unmeasured Osm

Question 15

Employee and foresnic tox requies?

Drug that is most common cause of childhood fatal OD, symptoms?

Answer 15

Chain of custody and confirmation (GC/MS)

Fe, strong oxidizing agent, NV, GI bleed, shock and lactic acidosis

>300 ug/dL risk for tox, >1000 ug/dL death is possible

Question 16

Acetaminophin used what to determine risk?

Avg toxic dose?

Answer 16

Rumackn ormogram; need 4 hours after ingestion.

15 g

Question 17

Which -OH does not cause acidosis in OD?

Methanol has what complication in OD?

Answer 17

Isopropanol

Optic neuropathy