14. Poisoning

Question 1

An OD P presents with hypertonia, hyperreflexia, extensor plantar reflexes and dilated pupils. What is the likely OD agent?

Answer 1

anti-cholinergics, e.g. TCAs

Question 2

An OD P presents with reduced consciousness, constricted pupils and hypoventiation. What is the likely OD agent?

Answer 2

opiates, e.g. heroin, codein

Question 3

A P has ECG abnormalities and hypokalaemia. What is the likely OD agent?

Answer 3

beta blockers

Question 4

Which antidote would you give in opiate OD?

Answer 4

naloxone IV infusion

Question 5

Which antidote would you give in benzodiazepine OD?

Answer 5

flumazenil

Question 6

Which antidote would you give in beta blocker OD?

Answer 6

atropine + glucagone

Question 7

Which antidote would you give in opiate OD?

Answer 7

N-acetylcysteine

Question 8

Which antidote would you give in digoxin OD?

Answer 8

digibind

Question 9

Explain the pathophysiology of paracetamol OD.

Answer 9

• Most paracetamol metabolised in liver to sulfate (30%) or glucuronide (60%).
• Small amount (10%) metabolised by P450 oxidation to toxic NAPQI (as other pathways are rate-limited)… conjugated with glutathione… inactive metabolites.
• In substantial OD, NAPQI conjugation is saturated due to glutathione depletion… liver toxicity.

Question 10

Name 3 ways in which pharmacokinetics are different in the elderly.

Answer 10

1. impaired 1st pass metabolism… increased drug bioavailability
2. reduced renal clearance… accumulation and ADRs
3. impaired hepatic clearance… accumulation and ADRs

Question 11

Name 2 ways in which pharmacodynamics are different in the elderly.

Answer 11

1. age-related reduction in R sites
2. reduced homeostatic reserve… increased sensitivity to drugs affecting postural control, cognitive function and visceral muscle function