Forensic Toxicology Question-Answer

By @forensicfield

Multiple choice questions with explanations.

1. Which of the following is NOT a side effect of Digoxin toxicity?

A. Bradycardia
B. Yellow vision changes
C. Scooping of the T segment on ECG
D. Hypokalemia

2. Which information can be obtained from an acute toxicity study?

A. Median toxic dose (TD50)
B. Median lethal dose (LD50)
C. No Observed Adverse Effect Level (NOEL)
D. Target organ
E. All of the above

3. A particular dose of a substance X is minimal toxic to animal. Substance Y is also minimal toxic to the animals at the same dose, but when both the substances are administered together they show the toxicity several orders of magnitude higher than compared with individual administrations. This is an example of:

A. Potentiation
B. Synergism
C. Additivity
D. Acute Toxicity
E. Agonism

4. Which of the following chelating agents is recommended for acute Lead poisoning with signs of encephalopathy?

A. Succimer
B. Penicillamine
C. Dimercaprol
D. Calcium EDTA
E. Dimercaprol + Calcium EDTA

5. Which of the following dermatologic findings and potential causes is INCORRECT?

A. Cyanosis- Methemoglobinemia
B. Erythroderma – Boric Acid
C. Pallor – Carbon Monoxide
D. Jaundice – Hypercarotinemia (excess carrot intake)

6. All of the following symptoms can occur with Ciguatera poisoning EXCEPT…

A. Myalgias
B. Flushing
C. Metallic taste
D. Reversal of temperature sensation

7. Which of the following is true with regard to Acetaminophen toxicity?

A. The Rumack-Matthew Normogram may be used for both acute and chronic ingestions.
B. The APAP level should ideally be checked within 1-4 hours of ingestion.
C. The Rumack-Matthew Normogram applies for ingestions up to 48 hours post-ingestion.
D. N-Acetylcysteine (NAC) should be started within 8 hours of ingestion if an APAP level cannot be obtained.

8. All of the following are treatment options for toxic alcohol poisoning, EXCEPT…

A. Fomepizole
B. Hydroxocobalamin
C. Thiamine
D. Folic Acid

9. Which one of the following are the main targets of lead toxicity?

A. Liver and kidneys
B. Nervous system and hematopoietic system
C. Heart and lung
D. Bones and muscles

10. ‘Itai-itai’ disease is caused by______

A. Cadmium
B. Mercury
C. Lead
D. Copper

Answers with Explanation:

1. Answer: D.

Despite the number of patients who come in taking Digoxin, it is important to remember that this medication comes with a large range of side effects. Bradycardia (along with any of the other SLUDGE Toxidrome symptoms) is a common effect due to the Parasympathetic activity of Digoxin. (Note: This is also the reason it works as a second-line agent for rate control of Atrial Fibrillation.) Yellow, halo-like vision changes (think Van Gogh’s ‘Starry Night’) are a more rare, but classic finding. The “scooped” ST segment is also a classic finding, commonly seen on ECGs – I recommend looking this up if you are not familiar with the appearance of this finding. Gynecomastia is an idiopathic and rare side effect of Digoxin. Finally, Hyperkalemia (Not Hypokalemia) occurs due to Digoxin’s primary effect on the Na-K ATPase Pump, blocking Na from leaving and K from entering the cell. It is also important to know that Hypokalemia can increase Digoxin’s toxicity by enhancing its binding to the Na-K ATPase Pump.

2. Answer: E.

In an acute toxicity study any end point parameter such as death, brain damage, liver damage etc. can be used to obtain information regarding a particular toxicant.

3. Answer: B.

In potentiation a non-toxic substance increases the toxicity of a relatively less toxic substance. In synergism a substance shows unusually high toxicity in presence of a less toxic substance, it is much greater than additive effect. In agonism a substance (agonist) mimics the mechanism of action of other substance, its opposite is known as antagonism.

4. Answer: E.

Succimer is the agent of choice for asymptomatic, mild Lead poisoning (45-70 mcg/dL in children, 70-100 mcg/dL in adults) because it is available PO and has a low side effect profile. Penicillamine is used predominately for the treatment of Wilson’s Disease (Copper chelation) and is no longer used in Lead toxicity due to its significant side effect profile. For severe toxicity with signs of encephalopathy, Dimercaprol (previously known as BAL; British Anti-Lewisite) is given IM followed by Calcium EDTA via continuous infusion to combine to chelate Lead from the brain and body, respectively.

5. Answer: C.

Methemoglobinemia causes cyanosis due to the oxidation of the Iron molecule in Hemoglobin, thereby reducing its Oxygen carrying capacity. Boric Acid (commonly found in a variety of products, but classically, pesticides) is well-known to cause a “boiled lobster” skin rash. Carbon Monoxide causes normal appearing or pink-colored skin due to its ability to increase Hemoglobin’s affinity for Oxygen, resulting in hyper-Oxygenated red blood cells. Hypercarotinemia, classically seen among anorexic and bulimic teenagers replacing high calorie foods with low calorie carrots, results in excessive beta-carotene, a yellow – pigmented vitamin which mimics jaundice.

6. Answer: B.

Ciguatoxin (found on warm-water, bottom-dwelling fish – including barracudas, sea bass, red snappers, grouper, and sturgeons, among others) binds to sodium channels and increases sodium channel permeability. This results in a variety of symptoms, such as diaphoresis, bradycardia, hypotension, abdominal pain, nausea, vomiting, diarrhea, metallic taste, myalgias, arthralgias, weakness, headache, ataxia, vertigo, sensation of loose and painful teeth, reversal of temperature sensation, peripheral and peri-oral paresthesias, and visual disturbances.

Flushing is a classic symptom of Scombroid toxicity. Recall that Scombroid poisoning is caused by Histamine-producing bacteria on the surface of improperly stored dark, tropical fish (e.g. tuna, mackerel, mahi-mahi, etc.). Symptoms include headache, abdominal pain, nausea, vomiting, diarrhea, peri-oral and peripheral paresthesias, dizziness, palpitations, and diffuse flushing of the skin.

7. Answer: D.

The Rumack-Matthew Normogram is a graph of “possible” and “probably” hepatic toxicity for ingestions ranging from 4-24 hours before measurement. It has been validated in multiple patient populations and is NOT valid for chronic ingestions or ingestions outside of the above time range. The APAP level should be checked between 4 and 24 hours post-ingestion (consistent with the range of the normogram), ideally within 4-8 hours of ingestion. Levels checked within 4 hours of ingestion are unreliable and will need to be rechecked at the 4-hour mark. Studies have shown that NAC is most effective when given within 8 hours of ingestion. If an APAP level will not be available at that time, NAC should be empirically started and can be stopped if the APAP level returns below the treatment threshold. Finally, Activated Charcoal may be used for acute ingestions within one hour (if the patient is not vomiting and protecting their airway), but should not be used beyond this time period.

8. Answer: B.

Ethylene Glycol toxicity is caused by the eventual conversion to Oxalic Acid, which causes renal toxicity. Methanol toxicity is caused by the eventual conversion to Formic Acid, which causes both renal and ocular toxicity. Fomepizole is an alcohol dehydrogenase inhibitor, which blocks the initial conversion of Ethylene Glycol to Glycoaldehyde and Methanol to Formaldehyde, thus decreasing the precursors to Oxalic and Formic Acid. Thiamine and Pyridoxine should both be given as 100 mg IV Q6H in suspected Ethylene Glycol poisoning. Thiamine is a cofactor involved in converting Glycolic Acid (a precursor to Oxalic Acid) to the non-toxic molecule, alpha-hydroxy-beta-ketoadipate. Pyridoxine is a cofactor involved in converting Glycolic Acid to the non-toxic molecule, Glycine. Folic Acid should be given as 1-2 mg/kg (up to 50 mg) IV Q6H in suspected Methanol poisoning. Folic Acid is a cofactor involved in converting the toxic Formic Acid to CO2 and H2O. Hydroxocobalamin is a treatment for Cyanide toxicity and has no role in toxic alcohol poisoning.

9. Answer: B.

Lead targets developing nervous system and shows severe effects in children. In adults mainly hematopoietic system is targeted.

10. Answer: A.

Itai itai is a cadmium poisoning disaster occurred around 1912 in Japan. The disease affected kidneys and bones causing severe pain in joints and spine, hence the name itai itai (“Ouch, Ouch” or “It hurts, it hurts”).


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