Rankin- Toxicology- (1)- Leah :) Flashcards
Main principle of toxicology?
Whats an LD50?
-Dose dictates toxicity
LD50, He says: “You might want to know this.*
- lethal dose in 50% of the population
- HIGH LD50 = SAFER
- LOW LD50 = DANGER
There are many scales for ranking the toxicity of substances…. what rating do they lack?
-NON-TOXIC; most any substance is toxic in a large dose
- # 1 cause of poisoning in the US?
- major sources?
- minor sources?
CARBON MONOXIDE
-colorless, odorless, tasteless= you don’t know you’re being exposed
-major sources: incomplete combustion of fossil fuels
(car exhausts i.e. Shane Gandee from Buckwild/ my high school, kerosine heaters, house fires)
-minor sources: cigarettes; hemolytic anemia, paint removers w/ methylene chloride
What two chemicals cause poisoning in house fires?
CO + cyanide
How does CO cause poisoning?
- Binds ferrous iron (Fe2+) in Hb = COHb
- Binds 250x tighter than O2–>
- DECREASE O2 carrying capacity of the blood
- INCREASE time to release O2 from Hb–> Tissue
= Anoxia –> main target = globus pallidus –> respiratory failure
= Cherry red mucus membranes
How is CO related to forensics?
In shootings, CO binds heme containing proteins (other than Hb) in tissues, when close up.
Short range gun wounds should have cherry range appearance, long range less likely to see red tissue.
(…..I think you would be red and bloody regardless, but whatever. Lol: he was really excited about that and the house fires. Haha)
At what level of CO is poisoning symptomatic?
-Mild sx up to 20-30% COHb
(person likely won’t know they are sick)
- Moderate symptoms at 40%+ COHb
(i. e. severe headache)
-70%+ COHb
(risk resp failure, death)
Treatment of CO poisoning?
- at 10-20%?
- At 20+% and severe H/A?
- At 50%+
- 10-20%: remove the source, get fresh air
- 20%+: give 100% O2
- 50%+: give 100% O2 + hyperbaric O2
How are patients exposed to CN? (4)
- occupational exposure (mining, chemical synthesis etc)
- certain drugs (i.e. laetrile for cancer)
- apricot or peach pits
- fires (esp if plastic is burnt)
How does cyanide cause poisoning?
- Inhibits electron transport chain
- Binds ferric iron (fe 3+) of cytochrome oxidase
Who is especially sensitive to cyanide?
- Children
- LD50 much lower possibly in kids due to less developed cellular machinery
Symptoms of CN poisoning
- RAPID progression (esp compared to CO)
- Nausea/ light headedness –> feeling of suffocation (can’t use O2 due to screwed up ETC) –> hyperventilation –> resp failure –> death (or severe brain damage)
Normal detoxification of cyanide:
- How is it detoxified in the liver?
- How does it get to the liver for detox?
Liver: Make thiocyanate, less toxic metabolite
CN + (S2O3)2- –> SCN- + (SO3)2-
via: sulfotransferase
-Binds ferric iron (3+) in methemoglobin in blood for transport to the liver (CN—FeHb complex)
How is cyanide poisoning reversed?
two steps
- Use oxidizing agent (i.e. sodium/amyl nitrite) to make more methemoglobin–> sequester CN
- Administer thiosulfate to ^^ sulfotransferase activity in liver
How do you lower methemoglobin levels post treatment for CN poisoning?
methylene blue (reducing agent, reduces Fe3+ to Fe 2+)
