Toxicology Flashcards
(16 cards)
What levels of paracetamol may be fatal?
75mg/kg for all adults
How do you manage a paracetamol OD?
ABCDE
Calculate the mg/kg of paracetamol likely to have ingested:
Give activated charcoal straight away if >150mg/kg and presents withing 1 hour
If >75mg/kg wait 4 hours then take paracetamol levels, treat is on or within 10% the line
If presents 8-16hrs after ingestion:
start NAC if ingested >75mg/kg straight away, take paracetamol levels and continue NAC if levels on or within 10% of the line
If presents 18-24hrs after ingestion:
if levels undetectable treat if in doubt
What is classed as a staggered OD and how do you treat it?
Staggered OD is taken >1hr
Cannot use the nomogram
Treat on the basis of the total consumed in the last 24hrs
and treat as per protocol
What about paracetamol metabolism makes it so dangerous in overdose?
Paracetamol is normally conjugated in the liver, when this pathway is exceeded it is metabolised by P450 to produce NAPQI which is congugated with glutathione to make it non toxic.
In an overdose the initial conjugation in the liver is exceeded and the glutathione stores are exceeded so the NAPQI cannot be conjugated. This leaves NAPQI in its toxic form which results in heptocellular damage
NAC is a gutathione doner so it reduces the NAPQI levels
how long on average does it take to eliminate a drug?
5 half lives
What measures can be done to decrease the absorption of a drug?
Gastric lavage - within 1 hour of ingestion of potentially lifethreatening OD
Activated charcoal - within 1 hour of ingestion. adsorbs most compounds except metals, acids/alkalis and alcohol
Whole bowel irrigation - consider for large OD of Iron and lihium, slow release preps and in body packers
What measures can be done to increase elimination of a drug?
Repeated doses of activated charcoal - useful for significant ingestions of theophylline, carbamazepine, pheobarbitone, quinine, dapsone
What are the features of TCA over dose?
Rapid onset of anticholinergic features:
Dowsiness, coma, convulsions
Sinus tachy with long QTc - VT
Hypotension
can give hypertonic sodium bicarbonate
When is giving flumazenil indicated in benzo OD?
Iatrogenic over sedation with benzos
Not routinely given in OD as can result in arrhythmias and convulsions
How do you work out the hourly infusion dose of naloxone?
It is 2/3 the inital dose required to wake the patient - not to completely withdraw them, just enough to improve RR and alertness
What is the antidote for B blockers?
Atropine
Then glucagon +5% dextrose if that fails.
Then pacing
What is the antidote for cyanide?
Sodium nitrate + sodium thiosulfate or
Dicobalt edetate + 50% dextrose or
Hydroxocobalamin 5mg over 30mins
What is the antidote for iron OD?
Desferrioxamine
What is the antidote for organophosphates?
Atropine
What do you give if someone ODs with ethylene glycol?
Ethanol
It is anti freeze
What do you give if someone ODs with methanol?
Ethanol
