70 - Toxicology II Flashcards
What are the receptor competitor therapies?
- Warfarin
- Opioids
- Competitive receptor antagonists (naloxone, naltrexone)
What is warfarin?
Anticoagulant that interferes with synthesis of vitamin K-dependent coagulation factors
What are the adverse symptoms of warfarin?
Adverse symptoms include hemoptysis, excessive bruising, bleeding from nose or gums, or blood in urine or stool
How do you treat bleeding and high INR due to warfarin?
Requires reversal by injection of vitamin K (phytonadione), or (in case of severe bleeding) prothrombin complex or fresh frozen plasma infusion to replace coagulation proteins
What are the opioids that are receptor competitors?
Heroin, morphine, meperidine, codeine, etc.
Describe the action of naloxone
Naloxone (Narcan®, Nalone®, and Narcanti®)
- Acts at µ, κ, and δ receptors to competitively block/reverse the effects of opiates
- Duration of action: ~45 minutes
Describe how naltrexone is different than naloxone
Naltrexone (Revia®)
- Same action as naloxone
- Longer duration of action (24-72 hrs) than naloxone
- Can also be used in withdrawal treatment
First use naloxone to save their life within minutes, then give naltrexone for maintenance to treat poisoning so the effects of the opioids don’t come back
What is methemoglobinemia?
- State in which the heme iron is in the Fe+3 state (ferric), and not Fe+2 (ferrous) of normal hemoglobin
- Methemoglobin, is unable to transport oxygen ***
What causes methemoglobinemia?
Caused by exposure to various chemicals (nitrites, sulfa drugs, many others)
What is the anecdote used to treat methemoglobinemia?
Methylene blue
How does methylene blue work?
Mechanism of Action: causes a direct chemical reduction of methemoglobin back to hemoglobin
What are toxidromes?
Toxidromes are common, and often well-characterized, clinical syndromes that provide a symptomatic fingerprint allowing for the successful recognition of patterns of poisoning associated with specific intoxicants
This means that in the ER, you see a certain set of symptoms, and you can match the toxidrome to the presenting patient in order to determine the cause of poison
Not “bullet proof” or 100%, but it gives you a good idea
What are the most prevalent clinical toxidromes?
- sympathomimetics
- sedative hypnotics
- opioids
- anticholinergics
- cholinergics
- tricyclic antidepressants (TCAs)
- salicylates
- acetaminophen
Describe the symptoms and cause of a sympathomimetic toxidrome
Cause = CNS stimulant (cocaine, amphetamines, PCP)
Pupils = mydriasis
Other = hypertension, tremor, hyperthermia
Describe the symptoms and cause of a sedative/hypnotic toxidrome
Cause = CNS depressants (alcohol, barbiturates, benzodiazepines)
CNS = coma
Respiration = decreased
Pupils = miosis or mydriasis
Other = hypotension
Describe the symptoms and cause of a opioid/opiate toxidrome
Cause = opiates, morphine, codeine, propoxyphene, oxycodone, hydrocodone
CNS = coma (decreased consciousness)
Respiration = depression
Pupils = “pinpoint” miosis
Other = hypothermia, hypotension, “opiate triad”, histamine release
Describe the symptoms and cause of a anticholinergic toxidrome
Cause = anticholinergics, antidepressants
CNS = agitation
Pupils = mydriasis
Other = fever, dry skin, flushing, urinary retention [hot, dry, mad, red, blind] ***
Describe the symptoms and cause of a cholinergic toxidrome
Cause = organophosphates/carbamates and other insecticides, nicotine
Pupils = “pinpoint” pupils (PPP)
Other = SLUDE - everything is wet
Describe the symptoms and cause of a tricyclic antidepressant toxidrome
Cause = TCAs (amitriptyline; imipramine; desipramine)
CNS = coma, agitation
Pupils = mydriasis
Other = dysrhythmia, convulsions, hypotension (due to alpha blockade)
Describe the symptoms and cause of a salicylate toxidrome
Cause = ASA, aspirin, other salicylates
Respiration = can increase or normal
Other = diaphoresis, tinnitis, agitation, alkalosis (early), acidosis (late), hyperpyrexia
A little less defined than some of the others
What are some of the other frequently encountered toxicants?
- Acidic substances (cleaners)
- Alkaline substances (cleaners)
In general, monitor ABCs and dilute with water to neutralize
How do you treat benzodiazepine poisoning?
Rarely fatal unless taken with ETOH or other CNS depressant due to synergistic CNS depression
Receptor antagonist: flumazenil
How do you treat acetaminophen poisoning?
Acetaminophen poisoning occurs after the depletion of glutathione - can result in hepatic necrosis, death due to hepatic failure
N-acetylcysteine (Mucomyst®) to restore glutathione
How do you treat cocaine overdose?
Cocaine overdose leads to cardiac dysrhythmias leading to cardiac arrest
Treat the dysrhythmia with lidocaine and monitor ABCs
