Overdose and Poisoning

Question 1

Management of paracetamol overdose

Answer 1

• <8 hrs after oral paracetamol ingestion (taken over <1 hr)
  
  • Consider activated charcoal if ingested <1 hour ago of >150mg/kg
  • For obese patients calculate if toxic dose
  • Measure paracetamol level 4 hrs from ingestion - await before deciding to treat
  • If biochemical results suggest acute liver injury double check timing of overdose and consider treatment with N-acetylcysteine (NAC) IV
  • Once plasma level is known revise treatment using nomogram
• 8-24 hrs after ingestion (taken over <1 hr)
  
  • Send urgent paracetamol level
  • Start NAC IV (do not wait on result)
  • If patient has ingested less than 150mg/kg await bloods before treatment
  • For obese patients calculate if toxic dose
  • If biochemical results suggest acute liver injury double check timing of overdose and consider treatment with N-acetylcysteine (NAC) IV
  • Discontinue NAC if plasma level below treatment line on nomogram
• >24 hrs from ingestion (taken over <1 hr)
  
  • Treat with NAC IV if:
    
    • Measured concentration is >5mg/L at >24 hours ingestion (indicative of a very large overdose)
    • ALT is above the upper limit of normal
    • INR is >1.3 (in the absence of any obvious cause)
    • Patient has jaundice or hepatic tenderness
  • Monitor bloods as well as VBG/ABGs
  • Discontinue NAC if plasma level below treatment line on nomogram
• Staggered overdose
  
  • Send for paracetamol level
  • Clinically significant toxicity is unlikely if, following at least 4 hours since the last paracetamol ingestion, the following criteria is met:
    
    • Paracetamol measured concentration is not detectable (<10mg/L)
    • INR ≤1.3
    • ALT is within normal limits
    • Patient asymptomatic (no symptoms to suggest liver damage)
  • If uncertain treat with NAC IV

Question 2

Management of salicylate poisoning

Answer 2

• Haemodialysis in severe cases

Question 3

Management of opoid overdose

Answer 3

• Naloxone

Question 4

Management of benzodiazepine overdose

Answer 4

• Majority managed with supportive care
• Flumazenil used in severe cases but can cause seizures

Question 5

Management of TCA overdose

Answer 5

• IV bicarbonate may reduce the risk of seiures and arrhythmias
• Class Ia and c antiarrhythmics should be avoided as they prolong depolarisation (i.e. Qunidine, Flecainide)
• Class III antiarrhythmics also contraindicated as they prolonge QT interval (i.e. Amiodarone)
• Dialysis is ineffective in removing tricyclics

Question 6

Management of lithium overdose

Answer 6

• Mild to moderate may respond to volume resuscitation with normal saline
• Haemodialysis may be needed in severe toxicity
• Sodium bicarbonate sometimes used

Question 7

Management of warfarin overdose

Answer 7

• Vitamin K
• Prothrombin complex

Question 8

Management of heparin overdose

Answer 8

• Protamine sulphate

Question 9

Management of beta-blocker overdose

Answer 9

• If bradycardic give atropine
• In resistant cases use glucagon

Question 10

Management of ethylene glyucol

Answer 10

• Fomepizole - inhibits alcohol dehydrogenase
• Ethanol can be used as it competes with ethylene glycol for the enzyme alcohol dehydrogenase - limits the formation of toxic metabolites responsible for haemodynamic/metabolic features
• Haemodialysis in refractory cases

Question 11

Management of methanol poisoning

Answer 11

• Fomepizole or ethanol
• Haemodialysis

Question 12

Management of organophosphate insecticides

Answer 12

• Atropine

Question 13

Management of digoxin overdose

Answer 13

• Digoxin-specific antibody fragments

Question 14

Management of iron overdose

Answer 14

• Desferrioxamine, a chelating agent

Question 15

Management of lead overdose

Answer 15

• Dimercaprol, calcium edetate

Question 16

Management of carbon monoxide poisoning

Answer 16

• 100% oxygen
• Hyperbaric oxygen

Question 17

Management of cyanide poisoning

Answer 17

• Hydroxocobalamin
• Also a combination of amyl nitrate, sodium nitrate, and sodium thiosulfate