Decontamination/Elimination/Antidotes Flashcards
What is decontamination?
stop ongoing exposure
-no longer in direct contact with the patient
to prevent absorption and thereby minimize systemic toxicity
decrease the possibility of transfer of the toxic substance
What are the principles of GI decontamination?
if a patient is already symptomatic, it means absorption has occurred and decontamination is unlikely to be benefit
-its efficacy decreases with time
prioritize airway protection and provide symptomatic and supportive care
risk vs benefit of GI decontamination is largely dependent on severity of potential toxicity
What is activated charcoals absorptivity attributed to?
its highly porous structure
What happens when toxicant and activated charcoal form a complex?
not systemically absorbed; therefore toxicant removed with AC upon bowel movement
Describe AC preparation.
derived from various organic materials
-e.g. coconut shells or peat
activated by heating at 600-900 C, then washing with inorganic acids and drying
creates highly developed internal pore structure
-small particle size with large surface area make it very adsorptive
allows for the adsorption of drugs and toxins through weak intermolecular forces
AC becomes less effective with use and have to be recharged or replaced
What are examples of agents that adsorb to AC?
acetaminophen
amitriptyline
amphetamines
chlordiazepoxide
cimetidine
codeine
diazepam
digoxin
salicylates
What are examples of agents that do not adsorb to AC?
boric acid
cyanide
ethanol
ethylene glycol
iron
lithium
malathion
methanol
petroleum distillates
What is sometimes added to AC to increase palatability?
sorbitol (sugar alcohol)
What is the dose of AC if the amount of toxicant ingested is known?
10-40x the dose of toxicant
When is AC more likely to reduce poison absorption?
if it is administered within 1 hour of ingestion
insufficient data to support or exclude the use of AC when more than 1 hour has passed since ingestion
When do we start AC method?
within 1 hour of ingestion (if feasible) but consider:
-bezoars
-MR products
-toxicants or co-ingestants that reduce GI motility/gastric emptying rate
-effect of volume ingested on gastric emptying rate
the above have benefits well beyond 1 hour
What are factors that increase AC appropriateness?
serious toxicity anticipated, no antidote
recent ingestion
alert, cooperative, intact airway
favourable stoichiometry
MR product
known to adsorb
no ileus/intestinal obstruction
opioids (can be given 2-3 hours after ingestion)
What are contraindications to AC?
toxicant known not to adsorb
unprotected airway (unconscious or trauma)
ingestion of hydrocarbons - risk of aspiration
risk of GI perforation (has ulcer, surgery, caustic agent)
endoscopy will be required (ex. corrosive)
What are examples of caustic agents?
drain cleaners
detergents
strong acids or alkali
What are complications of AC?
emesis
constipation/diarrhea
pulmonary aspiration
black stool/tongue/mucous membranes
pts with pre-existing motility disorders might be at greater risk
When is orogastric lavage considered?
ingested a potentially life-threatening amount of a poison and the procedure can be undertaken within 60 minutes of ingestion
What are practical indications for orogastric lavage?
toxicant likely to be life-threatening
OR obvious signs and symptoms of life-threatening toxicity
AND reason to believe significant amount in stomach
AND AC not an option
AND no spontaneous emesis
OR no highly effective antidote or alternative therapies pose high risk
What is whole bowel irrigation?
introduction of large amounts of fluid into GIT to expel intraluminary contents
rationale: cleanses bowel with large amounts of PEG solution to minimize drug absorption and expel intraluminal contents out of GIT; does not cause net change in ions, therefore no electrolyte imbalances
What are situations where WBI is an option?
expediting GI luminal clearance of:
-SR preparations
-toxic heavy metals
-packets of illicit drugs smuggled within the body
What is the evidence for WBI?
reported effective:
-decrease lithium concentrations
-98% success in body packers
-not effective for rapidly absorbed drugs
-may reduce hospital time, if successful
What are contraindications to WBI?
unprotected or compromised airways
GI compromises/hemorrhage
hemodynamically unstable
persistent vomiting
suspected leakage from drug packets or bowel obstruction or perforation
What are complications of WBI?
nausea/vomiting
abdominal cramping/bloating
aspiration/acute respiratory distress syndrome
hypo/hypernatremia
interreference with AC
What are some “other” methods of decontamination?
surgical removal
misc adsorbents
-Kayexalate
-cholestyramine
What is elimination?
enhances the removal of a toxicant that has already been systemically absorbed
removal from blood, therefore related to distribution or redistribution from tissues
When wont elimination methods have much effect?
if distribution is large
Vd > 1 L/kg considered large because it indicates that only a small portion of the total dose is in the plasma
What are the two types of elimination methods?
intracorporeal (occurring inside the body)
extracorporeal (occurring outside the body)
What is an example of an intracorporeal elimination method?
multiple dose activated charcoal
What are examples of extracorporeal elimination methods?
hemodialysis
hemofiltration
hemoperfusion
When does MDAC decrease absorption to tissues?
large amounts of xenobiotics are ingested, and dissolution is delayed (bezoars, SR, impaired GI motility)
when reabsorption can be prevented by lowering the concentration of free toxic substance in the intestinal lumen
How does MDAC work?
repeated administration of oral AC to enhance elimination to enhance elimination of drugs already absorbed into the body by functioning as an adsorbent “sink” at several sites in the gut
What is the dose for MDAC?
optimum dose unknown
dose and administration interval tailored to:
-amount and dosage form of xenobiotic ingested; severity of overdose; whether the patient is vomiting; potential lethality of xenobiotic; and tolerability
Which drugs have enhanced elimination from MDAC?
carbamazepine
dapsone
phenobarbital
quinine
theophylline
What are contraindications to MDAC?
patients with unprotected airways
if use is likely to increase risk and severity of aspiration
when threat of GI perforation or hemorrhage is high
when endoscopy is likely to be attempted
intestinal obstruction
when activated charcoal is known to not meaningfully adsorb the ingested toxin
if decreased peristalsis is likely to occur from the substance ingested
What are complications of MDAC?
constipation
bowel obstruction
emesis/aspiration
rectal ulcer/hemorrhage
reduction of therapeutically used xenobiotic
