Lecture 5 Clinical Toxicology - GI Decontamination, Supportive Care, and Antidotes

Question 1

What are the ABC’s to supportive care?

Answer 1

Airway - remove obstruction to airway, lay person on their side
Breathing - check for adequate oxygen and ventilation
Circulation - aid circulation by IV fluids and monitor by ECG

Question 2

What is always the gold-standard initial treatment for poisoning?

Answer 2

Supportive care

Question 3

What is a toxidrome?

Answer 3

Toxic syndrome

Question 4

Why is it difficult to identify what patient has overdosed in?

Hint: why can physical examination of the effects of overdose be deceiving?

Answer 4

Overdoses do not necessarily display textbook symptoms (uncommon!)
Multiple drugs responsible for overdose, some symptoms are expressed others are not
Drugs often have unique pharmacological effects in different people
Extent of overdose may display different symptoms.

Question 5

What possible investigations would be worthwhile?

Answer 5

ECG: monitor heart effects, many drugs cause adverse cardiac effects which are most likely to lead to death
Oximetry and arterial blood gases
Test drug levels: known drug ingested
Urine drug screen: known/suspected drug abuser but unknown drug ingested

Question 6

Name two antidotes.

Answer 6

Naloxone: antidote of opioid
Flumazenil: antidote of benzodiazepine

Question 7

Outline the mechanism of action of antidotes.

Answer 7

Act as competitive antagonists to the poison/drug.
e.g. pushes opioid off the receptor, a higher dose of opioid is required to cause the same effect because naloxone is binding to its receptors.

Question 8

What are the disadvantages of antidotes? (4)

Answer 8

Withdrawal effects (underlying symptoms that drug was treating resurfaces)
Costly
Has to be at right time (early), only of short duration.
May not be safe to use

Question 9

What is ipecac? And what is the current consensus on its use to treat poisoning?

Answer 9

Ipecac is forced emesis (induced vomiting).

Not beneficial, may force drug further down GIT. Less effective than other interventions, never used

Question 10

What is gastric lavage? And when is its usage most agreed upon?

Answer 10

A tube through the mouth or nose into the stomach. Toxicants are removed by flushing saline solutions into the stomach, followed by suction of gastric contents. Only beneficial for severe poisoning. Useful for patients who are already intubated, or supportive care is not adequate.

Question 11

What sort of drugs can be treated with activated charcoal?

Answer 11

Carbon-based drugs, that have suitable size so are big enough to bind to charcoal significantly

Question 12

How does activated charcoal work?

Answer 12

Activated charcoal is a strong absorbent, toxins bind to it and reduces toxin absorption and hence increase elimination.
Can even prevent enterohepatic recycling (excretion as bile, reenters GIT to be deconjugated and reabsorbed)

Question 13

What is whole bowel lavage?

Answer 13

Infusion of polyethylene glycol electrolyte lavage solution into the stomach to induce gastrointestinal dialysis

Question 14

What is whole bowel lavage used for?

Answer 14

Drugs that don’t bind to activated charcoal.

Sustained release preparations

Question 15

At what time period is suitable for gastric lavage?

Answer 15

<1hr

Question 16

At what time period is suitable for activated charcoal?

Answer 16

1-2hr

Question 17

Is methanol or its metabolites more toxic?

Answer 17

Methanol metabolites.

Formic acid inhibits mitochondrial oxidative metabolism causing increased lactic acid.