21- Case 21: Paracetamol Overdose (Not everything is covered, due to chatgpt filtering sensitive issues)

Page: 57-58

Correct answer: B. Administer activated charcoal

Explanation: Activated charcoal is indicated within 1 hour of ingestion to reduce gastrointestinal absorption. Paracetamol levels are unreliable before 4 hours, and NAC is started based on nomogram results or uncertainty.

A 24-year-old woman presents 45 minutes after ingesting 30 paracetamol tablets. What is the most appropriate immediate management?

A. Measure serum paracetamol level immediately
B. Administer activated charcoal
C. Start intravenous N-acetylcysteine
D. Observe only and repeat bloods in 24 hours
E. Administer Oral methionine

Correct answer: D. 4 hours post-ingestion or later

Explanation: Paracetamol levels should be measured at least 4 hours after ingestion, as earlier measurements do not accurately reflect peak absorption.

At what time after ingestion should a serum paracetamol level be measured to assess toxicity?

A. Immediately on arrival
B. 1 hour post-ingestion
C. 2 hours post-ingestion
D. 4 hours post-ingestion or later
E. 24 hours post-ingestion only

Correct answer: B. A patient on carbamazepine therapy

Explanation: Chronic use of enzyme-inducing drugs such as carbamazepine increases the risk of hepatotoxicity. Acute alcohol intake alone is not a risk factor.

Which of the following patients is at increased risk of hepatotoxicity at lower paracetamol levels?

A. A patient with acute alcohol intoxication
B. A patient on carbamazepine therapy
C. A patient with no medical history
D. A patient who presents early to hospital
E. A patient who took a single overdose

Correct answer: C. N-acetyl-p-benzoquinone imine (NAPQI)

Explanation: NAPQI is a toxic metabolite normally detoxified by glutathione. In overdose, glutathione is depleted, allowing NAPQI to cause hepatocyte damage.

The toxic metabolite responsible for liver injury in paracetamol overdose is:

A. Paracetamol sulfate
B. Glucuronide conjugate
C. N-acetyl-p-benzoquinone imine (NAPQI)
D. Methionine
E. Glutathione

Correct answer: D. Replenishes hepatic glutathione stores

Explanation: NAC replenishes glutathione, allowing detoxification of NAPQI and preventing liver injury.

What is the primary mechanism of action of intravenous N-acetylcysteine (NAC)?

A. Inhibits paracetamol absorption
B. Enhances renal excretion of paracetamol
C. Directly neutralizes paracetamol
D. Replenishes hepatic glutathione stores
E. Blocks cytochrome P450 enzymes

Correct answer: B. Liver function tests and INR

Explanation: LFTs and INR assess liver injury and synthetic function and are standard in overdose assessment.

Which investigation is routinely included in the assessment of paracetamol overdose in addition to serum paracetamol level?

A. Serum calcium
B. Liver function tests and INR
C. Creatine kinase
D. Troponin
E. Serum ammonia only

Correct answer: C. Impulsive self-harm with protective factors present

Explanation: The overdose was impulsive, followed by immediate regret, with good insight and future plans. Despite low–moderate risk, psychosocial assessment is still required.

Which statement best describes the psychiatric risk assessment in this patient?

A. High suicide risk requiring compulsory admission
B. Low risk; no psychiatric assessment needed
C. Impulsive self-harm with protective factors present
D. Chronic suicidal ideation
E. Psychotic depression

Correct answer: D. It is an alternative when IV NAC is unavailable

Explanation: Oral methionine may be used when IV NAC is unavailable, but NAC is the preferred and standard treatment.

Which statement regarding methionine use in paracetamol overdose is most accurate?

A. It is first-line treatment in all cases
B. It is superior to NAC
C. It is commonly used in modern UK practice
D. It is an alternative when IV NAC is unavailable
E. It has no role in treatment

Correct answer: B. Ingestion of multiple doses over several hours or days

Explanation: A staggered overdose refers to repeated supratherapeutic doses taken over time. These cases cannot be reliably assessed using the standard nomogram and are treated with NAC.

Which of the following best describes a staggered paracetamol overdose?

A. Ingestion of paracetamol with alcohol
B. Ingestion of multiple doses over several hours or days
C. Ingestion of paracetamol with another drug
D. Ingestion of paracetamol on an empty stomach
E. Ingestion occurring at night

Correct answer: C. Uncertain time of ingestion

Explanation: If the time of ingestion is uncertain, NAC should be started immediately as a precaution.

Which situation mandates immediate initiation of intravenous N-acetylcysteine without waiting for paracetamol levels?

A. Presentation within 1 hour of ingestion
B. Clear single overdose with known timing
C. Uncertain time of ingestion
D. Low paracetamol level at 4 hours
E. Normal liver function tests

Correct answer: D. INR

Explanation: INR reflects liver synthetic function and is a key prognostic marker in acute liver failure.

Which investigation is particularly important for assessing hepatic synthetic function in paracetamol overdose?

A. ALT
B. AST
C. Bilirubin
D. INR
E. Alkaline phosphatase

Correct answer: C. Immediate help-seeking after ingestion

Explanation: Immediate help-seeking and regret following the overdose are strong protective factors.

Which factor in this patient’s history is most protective against future suicide risk?

A. Female gender
B. Alcohol use prior to overdose
C. Immediate help-seeking after ingestion
D. Past history of self-harm
E. Argument with partner

Correct answer: C. To assess coping strategies and future risk

Explanation: Psychosocial assessment evaluates risk, coping skills, and the need for psychological or social interventions.

What is the primary purpose of a next-day psychosocial assessment following overdose?

A. To determine criminal responsibility
B. To decide on compulsory admission
C. To assess coping strategies and future risk
D. To prescribe antidepressants
E. To discharge the patient immediately

Correct answer: C. It guides the need for NAC in single acute overdoses

Explanation: The nomogram is used for single, acute overdoses with known timing and guides NAC treatment.

Which statement regarding the Rumack–Matthew nomogram is correct?

A. It can be used in staggered overdoses
B. It is valid before 4 hours post-ingestion
C. It guides the need for NAC in single acute overdoses
D. It replaces liver function testing
E. It is only used in children

Correct answer: B. Potentially hepatotoxic overdose

Explanation:
In adults, ingestion of ≥7.5 g (approximately 15 tablets) is potentially hepatotoxic. Thirty tablets clearly exceed this threshold and require urgent assessment and investigation. Food intake does not reduce toxicity.

Toxic Dose Recognition

A 24-year-old woman presents after ingesting 30 paracetamol tablets in a single episode. Which of the following best describes this ingestion?

A. Below the toxic threshold for adults
B. Potentially hepatotoxic overdose
C. Safe dose if taken with food
D. Only toxic if staggered
E. Unlikely to require investigation