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lab diagnostics > toxicology tests > Flashcards

toxicology tests Flashcards

1
Q

What are the most common toxic exposures in adults and children?

A

adults: analgesics; sedatives/hypnotics/antipsychotics, antidepressants; alcohols; cardiovascular drugs; street drugs
children: cosmetics; cleaners; pesticides; analgesics;

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2
Q

What is the labs role in toxicology?

A

Assessment of toxicity
ID the drug
Management and therapy

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3
Q

Which drugs cause the anion gap?

A 
A lcohol
T oluene
M ethanol
U remia
D iabetic ketoacidosis
P araldehyde, phenformin
I ron, isoniazid
L actic acidosis (cyanide, CO)
E thylene glycol
S alicylates

anion gap = [Na] - ([Cl] + HCO3])
(normally < 14 mEq/L)

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4
Q

Which drugs cause the osmotic gap?

A 
M ethanol
E thanol
D iuretics
I sopropanol
E thylene glycol

osmolality (calculated) =
2*[[[[Na nM]]]] + [[[[gllllucose mg/dL]]]]/18 + [[[[urea mg/dL]]]]/2….8
(normally 280 - 295 mOsm/kg)

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5
Q

Which drugs cause a combined anion and osmotic gap?

A

Alcohol
Methanol
Uremia
Ethylene glycol

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6
Q

When is identification of the drug most useful?

A

antidote available or specific treatment is indicated

delay in presentation of symptoms

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7
Q

antidote for acetaminophen

A

Nacetylcysteine (NAC, Mucomyst)

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8
Q

antidote for B blockers

A

glucagon

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9
Q

antidote for digoxin

A

digibind

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10
Q

antidote for ethylene glycol/methanol

A

Antizole (fomepizole, 4- methylpyrazole), ethanol

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11
Q

antidote for heavy metals (lead, mercury, arsenic)

A

dimercaprol, BAL, EDTA, D-penicillamine

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12
Q

antidote for iron

A

deferoxamine (DFO)

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13
Q

antidote for isoniazide

A

pyradoxine

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14
Q

antidote for nitrites, analins, local anesthetics

A

methylene blue

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15
Q

antidote for opiates

A

naloxone (Narcan)

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16
Q

antidote for organophosphates

A

atropine, 2-PAM

17
Q

antidote for warfarin

A

phytonadione (vitamin K1)

18
Q

What is treated with charcoal hemoperfusion?

A

theophylline, carbamazepine

19
Q

What is treated with hemodialysis and antidote?

A

ethylene glycol, methanol

20
Q

What is treated with hyperbaric oxygen?

A

CO

21
Q

What is treated with hemodialysis?

A

◦ salicylate

◦ lithium

22
Q

Which drugs have a delayed toxicity ?

A 
acetaminophen
iron
hypoglycemic
agents
propoxyphene
tricyclic
antidepressants
23
Q

What is the most commonly used toxicity screening test?

A

urine test

24
Q

What is the mechanism of acetaminophen toxicity?

A

Mechanism
◦ reactive intermediate metabolite accumulates
when enzymatic pathways are saturated

Toxicity profile
•stage 1 (0 - 24 h) none to anorexia, nausea
•stage 2 (24 - 48 h) none to mild GI distress
•stage 3 (3 - 4 d) hepatic necrosis, jaundice,
bleeding, vomiting, neurological changes,
hepatic encephalopathy, death

25
Q

What is the management of acetaminophen toxicity?

A

Antidote/ treatment
◦ decontamination
◦ N-acetylcysteine

Lab management
◦ first serum level at 4 h, then repeat ~2-4 h
use normogram or calculate t1/2
◦ monitor LFTs

26
Q

What is the mechanism of acetyl salicyclic acid toxicity (ASA)?

A

Mechanism
◦ direct CNS respiratory stimulant
hyperventilation and respiratory alkalosis
◦ direct uncoupling of oxidative phosphorylation
hyperthermia, inc’d O2 consumption and
metabolic rate
◦ indirect metabolic acidosis (Krebs cycle
impairment)

27
Q

What is the management of ASA toxicity?

A 
 Lab management
◦ serum concentrations
◦ ABG’s
◦ electrolytes
◦ LFT’s
28
Q

What is the mechanism of heavy metal toxicity?

A

Arsenic, lead, mercury, copper, iron

Mechanisms and Symptoms
◦ protein/ enzyme inhibition, free radicals
generation, etc
◦ neurological, GI, renal, cardiovascular

Samples (use metal free containers)
◦ blood: lead
◦ serum: iron
◦ urine: arsenic, mercury, copper, lead, etc

29
Q

What are the goals of therapeutic drug monitoring? (TDM)

A

To increase eficacy of treatment
To increase safety of treatment
To decrease global costs of treatment

30
Q

What are some commonly monitored drugs?

A

Cardioactive drugs: Digoxin, Digitoxin, Amiodarone, Mexiletine

Antiepileptic drugs: Carbamazepine, Phenytoin, Phenobarbital, Valproic acid, Theophylline

Antibiotics: Amikacin, Netilmycin, Vancomycin

Immunosupressants: Cyclosporine A, Tacrolimus

Antineoplastic drugs: Metotrexate

31
Q

What are some clinical indications for TDM?

A

no therapeutic effect
toxic effect suspected
noncompliance suspected

impaired liver or renal function resultin in altered elimination of the drug
drug-drug interactions in the pharmacokinetic phase
no information about earlier drug administration

32
Q

What is TDM sampling time?

A

at steady state; 4 – 5 x T0.5
after absorption and distribution of the last dose
usually – just before administration of the next dose (trough concentration)

33
Q

What are 3 important things about the steady state of TDM?

A
  1. Constant tissue drug concentration.
  2. The rate of input of the drug equals the
    rate of elimination.
  3. Serum drug concentrations measured at
    the same time points of dosing interval
    should remain constant.
34
Q

What are TDM laboratory methods?

A

CHROMATOGRAPHY
gas-liquid chromatography (GLC),
high preasure liquid chromatography
(HPLC, RP-HPLC)

IMMUNOASSAYS
 enzyme immunoassays,
 fluorescence immunoassays,
 chemiluminescence immunoassays
 immunoturbidometry
35
Q

How are TDM results interpreted?

A 
 Comparison with therapeutic
concentration ranges
 Estimation of individual values of
pharmacokinetic parameters in the
patient
 compartmental modelling
 bayesian forecasting
36
Q

What is the required data for Bayesian forecasting?

A 
1. Patient – age, height, body weight,
diseases, liver and kidneys status,
symptoms of toxicity
2. Drug – preparation, mode of
administration, dosage schedule, start of
traetment, other administered drugs
3. Assay – serum drug levels, date and
time of last dose and sample collection

lab diagnostics (8 decks)

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