Lecture 18: Poisons and poisoning

Question 1

What are some steps to diagnosing a suspected poisoning case:

Answer 1

• History
• Pupils
• Skin
• Odour
• Clinical chemistry (blood, urine)
• ECG

Question 2

Whats the value of history in an overdose?

Answer 2

History

• Patients rarely lie
• But may be unreliable
• > Sedation
• > Amnesic drug effects

Question 3

Constricted pupils indicate:

Answer 3

Constricted =

• Opiates (morphine)
• Clonidine
• Anti-cholinesterases

Question 4

Dilated pupils indicate:

Answer 4

Dilated

• Atropine
• Tricylic antidepressants
• Amphetamine / MDMA

Question 5

Sweating skin indicates:

Answer 5

Sweating:

• > Increased = Amphetamine
• > Decreased = Atropine

Question 6

What does bullae indicate?

Answer 6

Bullae (Blistering tissues b/c hypoxia)

• Carbon monoxide
• [Barbituates]

Question 7

What odours indicate?

Answer 7

Odours
-> Ethanol (smells drink)
-> Garlic
= Arsenic
= Organophosphates (insectiside)
-> Almonds
= Cyanide

Question 8

What blood chemistry can you find?

Answer 8

Blood

• Salicylate (aspirin)
• Paracetamol
• Ethanol
• CO
• Tricyclics
• Digoxin
• Theophylline

Question 9

What can you find in the urine?

Answer 9

• Salicylate
• Opioids
• Tricyclics

Question 10

What can be found on ECG?

Answer 10

ECG

• Long PR = Ca channel blocker (Verapamil)
• Wide QRS = Na channel (Amitriptyline)
• Long QT = Potassium channel (Amiodarone)

Question 11

Whats the immediate treatment for a poison suspect?

Answer 11

A = Airway
B = Breathing
C = Circulation

Question 12

What are the methods for treating drug overdose etc?

Answer 12

Decrease absorption
Increase elimination
Specific antidotes

Question 13

What are some methods for decreased absorption:

Answer 13

• [Emesis]
• [Gastric lavage]
• Activated charcoal (IMPORTANT)
• Fullers earth (or activated charcoal) for paraquat

Question 14

What are some methods of increased elimination:

Answer 14

• Activated charcoal (enteral dialysis)
• Haemoperfusion
• Haemodialysis

Question 15

Whats haemoperfusion used for?

Answer 15

Charcoal for theophylline

Ion exchange for salicylate

Question 16

Whats haemodialysis used for?

Answer 16

Methanol (wood alcohol)
Ethylene glycol (anti-freeze)

Question 17

What are five specific antidotes:

Answer 17

• N-acetylcystiene = Paracetamol
• Naloxone = Morphine
• Flumazenil = benzodiazepines
• Ethanol = methanol
• Fomepizole = Ethylene glycol, methanol

Question 18

What are four chelations used for antidotes?

Answer 18

Desferrioxamine -> Iron

Edetate -> Lead

Penicillamine -> Copper, mercury

Hydroxycobalamin -> Cyanide

Question 19

Whats an antidote for anti-cholinesterases OD?

Answer 19

Atropine / pralidoxime

Question 20

Whats an antidote for warfarin OD?

Answer 20

Vitamin K

Question 21

What are some protein binding agents?

Answer 21

Digoxin F (ab) -> Digoxin

Idarucizumab F (ab) -> Dibagatran

Andexanet -> Apixaban, Rivaroxaban

Question 22

Whats a specific antidote for paracetamol hepatotoxicity?

Answer 22

- Minor metabolite is NAPQI
= Formed by CYP2E1 (induced by ethanol)
- NAPQI inactivated by glutathione
- Liver damage caused by NAPQI
- Glutathione reserves used up by large doses

Question 23

What are the clinical applications of CP knowledge to OD?

Answer 23

Approach to poisonings

• ABC and general support
• Specific antidotes are uncommon
• Use physiology and pharmacology to assist in diagnosis
• Consider factors affecting drug clearance if enhanced elimination procedures if used.