Tox Antidotes Flashcards
What is the principal antidote to Methaemglobinaemia
Methylene Blue
10ml vial 1% solution (10mg/ml)
1-2mg/kg over 5 minutes followed by a flush
What is the antidote to local anaesthetic toxicity
Intralipid
20% vial 100mls (20mg/ml)
Bolus 1.5ml/kg (Approx 1 vial for 70kg Adult)
Then 15ml/kg/hr to max 12ml/kg
What is the antidote to Carbon Monoxide toxicity
Hydroxycobalamin
“Cyanokit” 5gm vials
Administer 5gm over 15mins, repeat up to 2 times every 30-60mins to max dose of 15gms
Children 70mg/kg
What is the antidote to Digoxin toxicity
Digibind (Digoxin Immune Fab) 40mg per vial
Intra-arrest dose 5 vials (200mg) Q5-10mins to max 20vials, in discussion with tox may give all 20 at once
Not arrested 2 (80mg) vials Q15mins, repeat doses as per toxicologist
Complications: Anaphylaxis, serum sickness, hypokalaemia, exacerbation of underlying heart failure or AF
What is the antidote to Dabigatran (Pradaxa)
Praxabind (Idarucizumab)
5gm as single IV bolus
What is the antidote to Benzodiazepines
Flumazenil
500mcg/5mls (100mcg/ml) ampoules
100-200mcg Q5mins to max 2000mcg
Paeds 5mcg/kg to max 1000mcg
Infusion 2-10mcg/kg/hour
What is the antidote to toxic alcohols
Fomepizole
- 15mg/kg loading dose
- 10mg/kg maintenance doses every 12hrs for 48hrs
- 1.5gm/1.5ml vial
Ethanol
1.8mls/kg (ie 4x 30ml shots vodka 70kg man) as loading dose
0.4ml/kg (30ml shot)/hr
Aiming BAC 0.1-0.15% or 0.1-0.15g/dl
What is the antidote to Sulphonylurea toxicity
Octreotide
Subcut: 50mcg Q8hr or 1-2mcg/kg in paeds
IV: 50mcg/kg bolus then 25mcg/hr infusion
Paeds 1mcg/kg bolus then 1mcg/kg/hr
What is the antidote to Organophosphate toxicity
Atropine
1.2mg bolus (0.05mg/kg) Q5mins until adequate atropinisation (Hr >80, SBP >80, chest clear)
IV infusion 10-20% of initial dose/hr
Pralidoxime
- 2gm loading dose
- 500mg/hr thereafter
- Paeds 25-50mg/kg load then 10-20mg/kg/hr
What is Calcium Gluconate used to treat?
1gm in 10ml vial (100mg/ml)
10% solution, 2.2mmol per vial
Hyperkalaemia
Hypermagnaesamia
Ca+ blocker toxicity
Hydroflouric acid exposure
Hypocalcaemia (ie ethylene glycol toxicity)
What is the antidote to Hydroflouric acid exposure
Calcium gluconate/Chloride
Systemic Flourosis: 6.6mmols IV over 5-10mins
Arrest: 2.2mmols every 5mins until ROSC
Dermal: Calcium gel, subcut calcium gluconate, intra-arterial infusion for limbs, and regional IV infusion
Biers block can be used to isolate an affected limb to prevent systemic flourosis and allow concentrated arterial/venous calcium infusions
What is the antidote to Valproate toxicity
L-Carnitine
- Carnitine involved in valproate metabolism
- depletion leads to conversion of Valproate to hepatotoxic form > hyperammonaemia and encephalopathy
Dose 100mg/kg bolus IV then 15mg/kg IV Q4hr-
What is the antidote in acute iron toxicity
Desferrioxamine (DFO)
5mg/kg/hr initial infusion, then increase by 2.5mg/kg/hr every 15mins to max 15mg/kg/hr
Max 80mg/kg in 24hrs
Indications
- Significant systemic toxicity
or
- Peak iron contentration >90umol/L (500ug/dl) at 4-6hr mark
- Peak concentration occurs 4-6hrs post IR OD and 7-9hrs post SR OD
What are the indications for DMPS in poisoning
Dimercaptopropane Sulfonate
Chelating agent for lead, arsenic and mercury
5mg/kg IV 4-6hrly
Indicated if symptoms consistent and serum levels of heavy metals high
What are the indications for Succimer in poisoning
AKA DMSA, AKA 2,3-dimercaptosuccinic acid
Chelating agent lead, arsenic and mercury
10mg/kg TDS for 5 days, then BD for 14 days
Should Antivenom have pre-treatment
Maybe
CSL recommends pretreating with adrenaline (0.25mls of 1:1000 S/C), but this is not backed up by Austin Tox
Which Australin non-snake envenomations have antivenom
Redback
Funnel web
Box Jellyfish
Stone fish
What are the indications for Digibind (Digoxin immune FAB)?
Acute (give 5 ampules)
- Cardiac arrest
- Unstable dysrhythmias
- Runs of VE’s
- Digoxin concentration >15 (12)
- K+ >6 in context of toxicity
Chronic (give 2 ampoules)
- Unstable dysrhytmias (fast or slow)
- Cardiac arrest
- Digoxin concentration >2 (1.6) + end organ damage, hyperK or VE’s
Other
- Other cardiac glycoside overdoses
What is the dosing of NAC and what are its indications?
Indications
- Paracetamol overdose
- Paraquat, Amanita phylloides
Adults
- 200mg/kg over 4hrs, then 100mg/kg over 16hrs
Children
- 200mg/kg (in 7mls/kg) over 4 hrs then 100mg/kg (in 14mls/kg) 16hrs
If in an acute ingestion paracetamol level is more than double the nomogram, > 30gm or >500mg/kg then double the 2nd bag to 200mg/kg
How does NAC work?
Antagonises the NAPQI toxic metabolite of paracetamol in 4 ways
- Increases glutathione production
- Direct binding of NAPQI
- Provision of inorganic sulfates (ie thiol) that bind NAPQI
- Can reduce NAPQI back to paracetamol
What are the complications and contraindications to NAC? When is it ok to cease NAC?
Relative contraindication is previous severe anaphylactoid reaction
- Anaphylactioid reactions occur 10-40% of cases, if it occurs then cease infusion, treat the reaction then slowly restart the infusion
- Pregnancy is not a contraindication
NAC can be ceased at 20hrs if
- Conc <10mg/L or 66umol/L
- ALT <50
- INR <2.0
- Patient clinically stable
What are the indications for Naloxone? How does it work?
Used prinicipally for opiates, can also be used for clonidine and Imidazoline overdoses with variable effect
Only indicated if the patient is unstable from an A/B/C point of view (ie would be intubated otherwise)
Competitive opioid receptor antagonist (mu, kappa, delta)
What is the onset and duration of Naloxone? What are the adverse effects?
IV 1-2mins
IM 5-6mins
IN 3-4 mins
Lasts 20-90mins
Nil adverse effects normally
In opioid dependence can precipitate acute withdrawal with GI upset (vomiting/aspiration) and catecholamine surge (APO, AMI, stroke, agitation, arrhythmias)
Paeds dose 10mg/kg
What is the therapeutic endpoint with naloxone? When and how should infusions be used?
End point- Awake and maintaining sats but not withdrawing
Patient may re-sedate with long acting opioids, if this occurs give 2nd bolus and start infusion 2/3rds the bolus dose per hour
If needing re-bolus then observe for 2hrs post
If needing infusion then observe for 4-6hrs post ceasing
