Poisoning

Question 1

Describe ADRs. (5)

Answer 1

An unwanted side effect of a drug at therapeutic doses. Can sometimes be used to our advantage eg chlorpromazine is a sedating antipsychotic now used in motion sickness.

Question 2

Define drug toxicity. (2)

Answer 2

Unwanted side effects at subtheraputic doses.

Question 3

Give 4 examples of drugs that have ADRs that are predictable extensions to the desired effect. (8)

Answer 3

Warfarin - bleeding / haemorrhage
Insulin - hypoglycaemia
Loop diuretic - hyperkalaemia
AChE inhibitors - SLUDGE syndrome

Question 4

Give 4 examples of drugs that have ADRs that are unrelated to the desired effect. (8)

Answer 4

Statins - rhabdomyalysis.
Beta agonist - palpitations, tachycardia
Thalidomide - teratogenic
Beta blocker - bradycardia

Question 5

Name two drugs that are co-prescribed to reduce their side effects. (4)

Answer 5

Methotrexate with folate suppliments

Chemotherapies with antiemetics.

Question 6

Describe two drugs with life threatening ADRs in large overdoses. (4)

Answer 6

Beta blockers - myocardial depression

Opioid - respiratory depression

Question 7

Give two examples of where you have to give additional agents to combat the specific biological toxicity of an agent. (4)

Answer 7

Acetylcysteine to treat NAPQI build up in paracetamol overdose
Mesna when prescribing cyclophosphamide to prevent haemorrhagic cystitis.

Question 8

Describe the immediate actions you would take if presented with a patient who had just overdosed. (4)

Answer 8

Remove person from contact with poisons (less relevant in A+E)
Vital sign measurements or injury
History - from patient if possible, chaperone, evidence (eg notes, packaging)

Question 9

Describe the recommmedned mechanism for preventing absorption of poisons. (5)

Answer 9

Activated charcoal.
Needs a 10:1g ratio with drug, which is a lot, and can be tricky to work out if you present after the fact.
Also aspiration risk.

Question 10

Why is gastric lavage never recommended? (1)

Answer 10

Very high risk of aspiration.

Question 11

Describe how you can encourage the elimination of poisons. (3)

Answer 11

Continue activated charcoal - esp in benzodiazepines / barbiturates
Sodium bicarbonate - esp in aspirin
Haemodialysis - only in seriously ill patients and with small Vd.

Question 12

Explain why forced diuresis is not recommended. (1)

Answer 12

Causes electrolyte inbalance.

Question 13

Give two examples of competitive antagonists that act as antidotes in overdose. (4)

Answer 13

Naloxone - opioids

Atropine - pesticide poisoning

Question 14

Describe the MoA of chelating agents acting as antidotes, and give an example. (4)

Answer 14

Complex with the poison to reduce free drug.

Sodium nitrate in cyanide / lead / mercury poisoning.

Question 15

Give two examples of drugs that manipulate metabolism of poisons. (4)

Answer 15

Acetylcysteine in paracetamol overdose

Ethanol in antifreeze / methanol poisoning