L18. Poisons and Poisoning

Question 1

What are the types of drugs that cause constricted pupils - enhance parasympathetic / decrease symp stimulation

Answer 1

• Opiates (morphine),
• Clonidine - Alpha2 agonist in the brain
• Anticholinesterases (neostigmine)

Question 2

What are the types of drugs that cause dilated pupils - enhance symp / decrease parasymp stimulation

And what other symptoms are associated with those drugs

Answer 2

Atropine- blocks Ach activity. Also causes decreased sweating

Amphetamine/MDMA/BZP- releases NA. Also causes increased sweating

Tricyclic antidepressants (Amitriptyline)

Question 3

What drugs cause Bullae and what is that

Answer 3

Bullae= large blister containing serous fluid.

Caused by carbon monoxide and barbiturates due to tissue hypoxia

Question 4

What drugs smell like garlic and almonds

Answer 4

Garlic: arsenic, organophosphates (anticholinesterase)
Almonds: Cyanide

Question 5

What drugs can be measured from the urine, blood or both

Answer 5

Both: salicylate (aspirin), Tricyclics
Urine only: opioids

Blood only: paracetamol, ethanol (also by breath), CO by change in Hb binding, digoxin, theophylline

Question 6

What type of drug causes a Long PR , Wide QRS complex , Long QT complex on an ECG- 3 different drugs

Answer 6

Long PR: Ca2+ channel blocker delays conduction at the AV node - eg. Verapamil

Wide QRS: Na+ channel blocker, delays AP spread in purkinje fibres - eg Amitriptyline (3cycl)

Long QT: K+ channel blocker- affects repolarisation- eg. Amiodarone

Question 7

What is the 4 major things done in treatment of poisoning in time order

Answer 7

1. General support for Airway, breathing and circulation
2. Decrease absorption of drug
3. Increase elimination
4. Use a specific antidote

Question 8

What are some treatments to decrease absorption of drug

Answer 8

Activated charcoal in absorbs liquid toxins before it can be absorbed by the gut.
Fuller’s earth is used for paraquat herbicides

Question 9

How is Methanol and ethylene glycol poisoning treated to increase elimination and what is the antidote used

Answer 9

Haemodialysis helps to remove small molecules.
Antidote= ethanol for methanol poisoning- competing for AD stop making formaldehyde.
Fomepizole- for both, inhibits AD.

Question 10

How does AC and Haemoperfusion help to increase elimination

Answer 10

1. Activated charcoal-mops up the drug and takes it to the faeces- however it passively diffuses across the gut wall- conc dependent
2. Haemoperfusion is short term, passing blood over a column of charcoal or ion exchange - trapping salicylate in the resin

Question 11

What is the antidote for morphine and antidote for benzodiazepines (eg. diazempan) overdose

Answer 11

1. Mo- Naloxone: opioid antagonist reverses mo effects

2. BZ-Flumazenil: antagonist

Question 12

What is the specific antidotes for metal poisoning, anticholinesterase, warfarin, Protein binding drugs (eg. digoxin)

Answer 12

1. Metal: chelation
2. anticholinesterases: Atropine blocks muscarinic receptor/pralidoxime reactivating cholinesterase
3. Warfarin: Vitamin K1
4. Antibody (eg. digoxin F(ab)

Question 13

What causes paracetamol hepatotoxicity and what is the specific antidote

Answer 13

• Paracetamol metabolites is NAPQ1 formed by CYP2E1 (up regulated by continued drinking which is a protective factor until stopped). It cases liver damage but
  It is inactivated by glutathione -which gets depleted in overdoses.
  Antidote N-Acetylcysteine supples SH to make more glutathione.

Treatment with this antidote dependent on concentration in the blood after 4 hours above or below a line of hepatotoxicity - 2 hr for children bc elixir is faster absorbed.

Question 14

What are the chelation agents for iron, lead, mercury+ copper and cyanide poisoning

Answer 14

Iron: desferrioxamine
lead: edetate
mer+cop: penicillamine
cyanide: hydroxocobalamin

Question 15

What are the protein binding agent for digoxin, dabigatran, apixaban + rivaroxaban

Answer 15

digoxin Fab
dabigatan: idarucizumab Fab
apixa + rivaro: andexanet