S1B5 - Toxicology Flashcards
A 12-year-old is brought to the ER after his teacher notices that the child is walking abnormally. The teacher is concerned about an injury or abuse. Examination of the child reveals that his right toe drags the floor and foot seems to slap on the group when he walks. A X-ray of both lower legs reveal normal findings. Examination of his mouth reveals purple lines on his gingiva. What is the diagnosis?
A) Arsenic poisoning
B) Child abuse
C) Lead poisoning
D) Iron poisoning
E) Foot injury
Lead poisoning
Answer Explanation
The child above has lead poisoning, which manifests with peripheral neuropathy such as foot and wrist drop. Foot drop occurs because of injury to the common or deep peroneal (fibular) nerves. As a result, there is weakness of the tibialis anterior muscle, and the foot is unable to be dorsiflexed. Thus, when the patient walks, his foot will slap the floor. Further, the purple lines on gingiva are a hallmark finding in lead poisoning. Typically, these symptoms are subacute and not seen by family members. In fact, several family members living in lead contaminated housing projects may be unaware that they have similar symptoms. Arsenic poisoning would show fingernails with white horizontal lines (Mees lines). Iron poisoning would manifest with bloody diarrhea and metabolic acidosis.
What is the antidote for anti-cholinesterase and organophosphate toxicity?
The antidote for anti-cholinesterase and organophosphate toxicity is atropine and pralidoxime.
What symptoms are associated with benzodiazepine toxicity? What is the antidote?
Symptoms associated with toxicity include:
- Apnea
- Drowsiness
- Respiratory depression (when combined with depressants e.g. alcohol)
The antidote for benzodiazepines toxicity is flumazenil (GABA-receptor antagonist).
How does the toxic metabolite of acetaminophen affect the liver? Describe the pathophysiological mechanism and specific liver zone damaged.
Normally, acetaminophen is conjugated in the liver to inactive metabolites. However, a fraction becomes hydroxylated to N-acetylbenzoiminoquinone (NAPQI), which is a toxic metabolite.
- At normal therapeutic doses, this is not clinically significant because NAPQI reacts with sulhydryl group of glutathione molecules in liver and is converted to a nontoxic metabolite, which is excreted in urine.
- In an overdose, glutathione molecules in liver are depleted and accumulated NAPQI reacts with sulfhydryl groups of hepatic proteins causing zone III centrilobular hepatic necrosis (potentially life-threatening)
On autopsy, the death of a patient was identified due to arsenic poisoning. Which of the following may have prevented the death of this patient?
A) Dimercaprol and gastric cleavage
B) Deferoxamine
C) Atropine
D) N-Acetylcysteine
E) NH4Cl
Dimercaprol and gastric lavage
Answer Explanation
Arsenic, Gold, Mercury, and Copper can all be sequestered from blood proteins through the chelating effects of Dimercaprol (think American GMC cars = Caprol). Iron and Lead require deferoxamine and EDTA, respectively.
What symptoms are associated with arsenic poisoning?
Symptoms of arsenic toxicity include:
- Garlic smelling breath
- Rice-water stools
- CNS symptoms (seizures, altered mental status, coma)
- Mees’s lines (white horizontal lines on fingernails)
- Vomiting
What symptoms are associated with anticholinergic toxicity? What is the antidote?
Symptoms of anticoholinergic toxicity include:
- Fever (hot as a hare)
- Mydriasis/blurry vision (blind as a bat)
- Anhidrosis (dry as a bone)
- Flushing (red as a beet)
- Delirium (mad as a hatter)
What symptoms are associated with copper, gold, or mercury poisoning?
Symptoms associated with toxicity include:
- Anemia
- Convulsions
- Liver failure
- Myopathy
- Skin discoloration
- Peripheral neuropathy
What are some common causes of mercury poisoning?
Mercury poisoning is usually the result of overconsumption of fish or improper disposal of fluorescent light bulb or spills.
In pharmacology, which order kinetics is saturable?
Zero order kinetics are saturable.
First order kinetics are not saturable.
What symptoms are associated with lead poisoning?
Symptoms associated with lead toxicity include:
- Microcytic anemia
- Abdominal pain
- Purple lines on gingivae
- Peripheral neuropathy (wrist and foot drop)
- Ataxia
A child is brought to the ER after the mother reported that he swallowed several iron pills. The child has abdominal pain and bloody diarrhea. Which of the following drugs is an antidote to iron poisoning?
A) Deferoxamine
B) Methylene blue
C) Penicillamine
D) EDTA
E) Dimercaprol
Deferoxamine
Answer Explanation
Deferoxamine is the chelating agent used bind free iron in the blood stream and enhancing its elimination in the urine. Deferoxamine is also used to treat iron excess states, such as hemochromatosis. EDTA, Penicillamine, and Dimercaprol are used to treat lead poisoning. Methylene blue is used to treat methemoglobin toxicity.
What is the most common cause of copper poisoning?
The most common cause of copper poisoning is Wilson disease.
- Copper poisoning from massive overdose of copper-containing foods or drugs is extremely rare.
What symptoms are associated with opioid toxicity?
Symptoms associated with overdose include:
- Apnea/respiratory depression
- Miosis (except meperidine, an opioid which can cause mydriasis due to muscarinic antagonism)
- Sedation
- Constipation
What are the 3 components of the treatment of β-blocker toxicity?
The treatment for beta blocker toxicity is:
- Glucagon, which increases cAMP in cardiac tissue
- Saline
- Atropine
What is the antidote for opioid overdose?
The antidote for opioid overdose is naloxone.
Dimercaprol can be used to treat all poisoning of all of the following, EXCEPT:
A) Gold
B) Mercury
C) Iron
D) Arsenic
Iron
Answer Explanation
Dimercaprol is a chelating agent that can be used to treat poisoning with “American GMC car” arsenic, gold, mercury, and copper (first-line treatment of copper is penicillamine, but dimercaprol can be used). Iron poisoning is treated with deferoxamine; it acts as a chelating agent that binds to free iron in the bloodstream. An easy way to remember this is that hemoglobin contains ferrous iron elements, and iron poisoning is treated with deFERoxamine.
What symptoms are associated with iron poisoning?
Symptoms associated with iron toxicity include:
- Confusion
- Bloody diarrhea (acute GI bleed) or metabolic acidosis (chronic iron exposure)
- With chronic iron overload hemachromatosis may develop - restrictive cardiomyopathy, joint pain, brittle diabetes and bronze coloring of the skin (all due to iron deposits)
What is therapuetic index a measure of?
Measurement of drug safety.
TITE: Therapeutic Index = TD50 / ED50.
Safer drugs have higher TI values. Drugs with lower TI values include digoxin, lithium, theophylline, and warfarin.
LD50 (lethal median dose) often replaces TD50 in animal studies.
TD50 = median toxic dose ED50 median effective dose
Therapeutic window—measure of clinical drug effectiveness for a patient.
