69/70: Toxicology Flashcards
primary determinant of toxicity **
dose
time is the other determinant (duration of time that chemicals present in body)
Q1: What was the does? How much did the person ingest?
Q2: How long ago?
dose at which 50% of tested animals die
LD50
TD50 = dose at which 50% have toxicity
legally, a poison has an LD 50 less than 50 mg/kg/bw
therapeutic index =
LD50/ ED50
the LARGER the number, the SAFER the drug
how is the ALD average lethal dose calculated?
estimated from accidental deaths in humans
give for narcotic overdose
naloxone
toxidromes =
known toxicology standards
emesis inducers
to remove unabsorbed toxicants from GI tract
- mechanical
- Apomorphine
- syrup of Ipecac
could also use gastric lavage (stomach pump)
contraindications to the use of emesis inducers
- petroleum hydrocarbon solvent (chemical pneumonitis)
- caustic acid or alkali agent ( rupture)
- seizing or comatose pt
why would you use activated charcoal ?
very lg SA allows binding of organic toxicants which prevents absorption
induces emesis
administered orally in water
pralidoxime/ 2PAM is an antidote for?
treat poisoning by organophosphates
it is a nucleophilic reagent that covalently binds to organophosphates and permits rapid exretion
usually administered with ATROPIEN to block muscarinic effects of parasymptathetic nervous system
what do you administer as antidote for cyanide poisoning?
amyl nitrite (inhaled) followed by sodium nitrite (IV) then sodium thiosulfate (IV) with O2 and whole blood
cyanide - death in 1-15 min because disrupts ETC (block cytochrome c oxidase) - no more ATP production
how do you treat botulinum toxin?
with antibodies formed in horse directed at botulinum toxin
single 10 mL vial/pt
botulinum toxin is most potent poison known, rapidly absorbed and prevents ACh release from n. terminals. most commonly affects respiratory depression.
how do you treat heavy metal intoxication?
chelators - bind with metal making them inert and increasing renal excretion
ex: BAL
Use: DMSA, succimer
tx of arsenic, mercury and LEAD poisioning
adults and kids over 12: 10mg/kg/PO, q8h for 5 d
children under 11: 10mg/kg/PO q8h for 5 d THEN q12h for 14d (19 d therapy)
adverse rxns: unpleasant odor to urine, sweat, feces, loos stools, loss of appetite,
ethylene glycol =
antifreeze
methanol is converted into formaldehyde and formic acid by …
how do you save?
alcohol dehydrogenase
ethanol admin competitively prevents alcohol dehydrogenase from converting these substances (ethylen glycol/methnaol/isopropyl alcohol) into toxic forms
hemodialysis is given as adjunct
also give FOMEPIZOLE - blocks alcohol dehydrogenase
drug of choice for antidotal therapy for ethylene glycol or methanol toxicity
fomepizole
treatment for carbon monoxide poisoning (cherry red appearance)
artificial respiration with pure O2 to promote displacement of CO; hyperbaric oxygen chamber if symptomatic
warfarin reversal =
injection of vit K or prothrombin complex or FFP infusion to replace coagulation prtns
s/s hemoptysis, excessive bruising, bleeding from nose or gums, or blood inurine or stool
MOA naloxone
acts at mu, kappa and delta receptors to competitively block/reverse teh effects of opiates
- 45 min duration of action
use opiod overdose - fast acting
MOA naltrexone
- same at naloxone (competitive inhibitor) but longer duration of action (24-72 hrs)
use opiod overdose – follows nalterxone, also withdrawal treatment
used to treat methemoglobinemia
methylene blue
cause a direct chemical reduction of methemoglobin back to hemoglobin
define toxidromes
common and well-characterized clinical syndromes that provide a symptomatic fingerprint allowing for recognition of patterns of poisoning associated with specific intoxicants
mydriasis
HTN
tremor
hyperthermia
sympathomimetic toxidrome
drugs: cocaine, amphetamines, PCP
coma
decreased respiration
miosis or mydriasis
hypotension
sedative/hypnotic toxidrome
drugs: alcohol, barbiturates, benzodiazepines
coma depressed respiration pinpoint pupils hypothermia hypotension histamine release
opioid toxidrome
drugs: heroin, morphine, codeine, propoxyphene, oxycodone, hydrocodone
opiate triad = hypothermia, hypotension and histamine release
agitation mydriasis fever dry skin flushing urinary retention
anticholinergic toxidrome
hot dry mad red blind
drugs: anticholinergics, antidepressants
SLUDE salivation lacrimation urination defecation
pinpoint pupils
cholinergic toxidrome
drugs: organophosphates (insecticides) , nicotine
diaphoresis tinnitis agitation alkalosis early, acidosis late hyperpyrexia
salicylate toxidrome
drugs: ASA
flumazenil
benzo overdose tx
n-acetylcysteine
acetaminophen overdose tx
restores glutathione (liver toxicity)
