Rankin - General Toxicology Flashcards
Fact:
Remember, ALL SUBSTANCES are toxic.
A principle of Toxicology is the dose dictates toxicity.
______ is the lethal dose in 50% of population. It is the dosage causing death in 50% of exposed animals.
The lower the ______, the more toxic the substance.*****
LD50
What toxic substance?
- colorless, odorless and tasteless gas
- exposure not detected by senses
Major Sources: incomplete combustion of fossil fuels (i.e. car exhausts; kerosene heaters) and fires (i.e. home fires)
Other Sources: cigarette smoke, hemolytic anemia, biotransformation of paint removers (i.e. methylene chloride)
Carbon Monoxide (CO)
Mechanism of Carbon Monoxide (CO) Toxicity.
- binds to ferrous (Fe2+) iron in Hb to form _________________ (COHb)
- ___________ Color in mucus membranes
- binds 250x tighter to Fe2+ in Hb than O2 reducing the O2 carrying capacity of the blood
- O2 bound to COHb is released _________ (faster/slower) than from Hb to further reduce O2 delivery to tissues
Result: Anoxia - decrease oxygen floating around in the body
carboxyhemoglobin
Cherry Red
slower
What is the #1 cause of death from poisoning in the US?
Death is due to _____________ failure.
What is the target organ in the CNS?
Carbon Monoxide (CO)
Respiratory failure
****Globus pallidus in the cerebellum
Fact: Clinical Effects of CO
Carbon Monoxide toxicity is reveresible.
At what level of COHb % would you begin to treat with 100% Oxygen?
20-30% mild poisoning
What toxic substance?
-exists as solid (Salt form), liquid (HCN) or gas
-occupational exposure during mining, chemical synthesis and electroplating
- ingestion of apricot or peach pits, bitter almond
- excess dose of certain drugs, laetrile
- fires
Cyanide (CN) and CN releasing agents
What toxic substance?
- mitochondrial toxin inhibiting electron transport chain
- binds to Ferric (Fe3+) iron of mitochondrial cytochrome oxidase inhibiting ETC between Cyta2 and Cyta3
- Lethal Dose: 50 mg adults (1 tsp); 1.5 mg children
Cyanide (CN)
Symptoms for what toxicity?
- rapid progression from onset of symptoms to death
- Nausea, lightheadedness, hyperventilation, feelings of suffocation, convulsions, coma
- HR increased followed by decreased HR
Cyanide Toxicity
Cyanide Poisoning.
Death from ____________ failure.
In recovered patients, what kind of damage might you see?
respiratory failure
Brain damage
Normal Detoxification of Cyanide in the Body occurs in the _________ (what organ)?
Liver (80%)
Treatment for CN Toxicity is a 2 Step Process.
Step 1: Administer __________ or ______________ to convert Hemoglobin (Hb-Fe2+) to Methemoglobin (Hb-Fe3+).
Methemoglobin binds the CN- forming cyanomethemoglobin (Hb-Fe3+-CN-).
Step 2: Administer ____________. Why?
nitrite (NaNO2 3% IV) or amyl nitrite ampule
Thiosulfate; allows the liver enzyme, su;fotransferase to lessen the toxicity of Cyanide and prepare if for excretion from the body.
What is the antidote for increased levels of methemoglobin in the blood?
Note: Methemoglobin can cause similar symptoms as Carbon Monoxide poisoning.
Methlyene Blue***
Insecticides.
Name 2 Organophosphate Insecticides.
Which is more toxic?
Name the Carbamate Insecticide.
1. Diazinon LD50 100-150 mg/kg (*MORE TOXIC)
2. Malathion LD50 1000-1375 mg/kg
Carbaryl (Sevin Dust)
What is the treatment for Organophosphate poisoning?
Atropine and Pralidoxime (2-PAM)
Pralidoxime (2-PAM) is a regenerating agent if given early enough.
Name the Insecticide.
Mechanism of toxicity: redox cycling molecule and as it shifts back from reduced form to oxidized form it generates free radicals leading to lipid peroxidation, membrane damage and tissue death
Paraquat
