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MRCP Pharmacology > Management of Overdose/Toxicity > Flashcards

Management of Overdose/Toxicity Flashcards

1
Q

Management of paracetamol overdose

A

if <1hr ago - activated charcoal
N-acetylcysteine
Liver transplantation

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2
Q

Naloxone is the antidote for an overdose of which substance?

A

Opioids/opiates

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3
Q

A severe overdose of benzodiazepines is treated with which antidote?

A

Flumanezil
- only used with severe or iatrogenic overdoses
- due to seizure risk

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4
Q

Management of tricyclics overdose

A

IV bicarbonate
- correct acidosis
=> may reduce risk of seizures and arrhythmias in severe toxicity

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5
Q

Dialysis is ineffective in removing tricyclics from the circulation. TRUE/FALSE?

A

TRUE

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6
Q

What antiarrhythmics should NOT be used in Tricyclic overdose?

A

Class 1a (e.g. Quinidine)
Class Ic antiarrhythmics (e.g. Flecainide)

Class III (Amiodarone)

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7
Q

Methods of managing lithium toxicity/overdose

A
  • mild-moderate = IVF with normal saline
  • haemodialysis if severe toxicity
  • sodium bicarbonate increases the alkalinity of the urine => promotes lithium excretion
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8
Q

Reversal agent for warfarin

A

Vitamin K
Prothrombin Complex

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9
Q

Heparin reversal agent

A

Protamine sulphate

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10
Q

Management of beta-blocker toxicity/overdose

A

Atropine if bradycardic
in resistant cases, glucagon may be used

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11
Q

Management of organophosphate insecticides toxicity/overdose

A

Atropine

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12
Q

Treatment of digoxin toxicity?

A

Digoxin-specific antibody fragments

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13
Q

Iron overload

A

Desferrioxamine, a chelating agent

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14
Q

Mechanism of action of cocaine

A

blocks uptake of:
dopamine, noradrenaline and serotonin

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15
Q

Cardiac adverse effects of cocaine

A
  • coronary artery spasm
  • MI
  • tachycardia/bradycardia
  • hypertension
  • QT prolongation
  • aortic dissection
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16
Q

Neurological adverse effects of cocaine

A

seizures
mydriasis (dilated pupils)
hypertonia
hyperreflexia

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17
Q

Management of cocaine toxicity

A

Chest pain:
benzodiazepines + GTN

HTN:
benzodiazepines + sodium nitroprusside

18
Q

Features of ecstasy overdose

A

Neuro:
- agitation
- anxiety
- confusion
- ataxia

cardio:
- tachycardia
- hypertension

Other:
hyponatraemia
hyperthermia
rhabdomyolysis

19
Q

Management of ecstasy overdose

A

Supportive

Dantrolene may be used for hyperthermia

20
Q

Drugs which can be cleared with Haemodialysis

A

BLAST

Barbiturate
Lithium
Alcohol (inc methanol, ethylene glycol)
Salicylates
Theophyllines

21
Q

Drugs which can’t be cleared with haemodialysis

A

tricyclics
benzodiazepines
dextropropoxyphene
digoxin
beta-blockers

22
Q

What treatment can be given for paracetamol overdose if the patient presents within 1 hour of ingestion?

A

Activated charcoal

23
Q

When should NAC be used?

A
  • plasma conc above treatment line
  • staggered overdose
  • patients presenting 8-24 hours after ingestion of >150 mg/kg of paracetamol
  • patients who present > 24 hours if jaundiced or have hepatic tenderness, or their ALT is above the upper limit of normal
24
Q

What adverse reaction can NAC cause and how is this managed?

A
  • anaphylactoid reaction (non-IgE mediated mast cell release)
  • Stop infusion, then restart at a slower rate.
25
Q

Criteria for liver transplantation in paracetamol overdose

A

Arterial pH < 7.3, 24 hours after ingestion

OR all of the following:
- PT > 100 seconds
- Creatinine > 300 µmol/l
- Grade III or IV encephalopathy

26
Q

How does paracetamol cause liver damage?

A
  • liver normally conjugates paracetamol with glucuronic acid/sulphate
  • conjugation system becomes saturated => oxidation by P450 system to form toxic metabolite (N-acetyl-B-benzoquinone imine)
  • Glutathione conjugates with toxin to form mercapturic acid
  • glutathione stores run-out
  • toxin forms covalent bonds with cell proteins, denaturing them and leading to cell death.
27
Q

How does NAC help in the management of paracetamol overdose?

A

NAC = precursor of glutathione

=> increases hepatic glutathione production
=> can conjugate with toxin

28
Q

What patient groups are at increased risk of hepatotoxicity in paracetamol overdose?

A
  • Those taking liver enzyme-inducing drugs
    (rifampicin, phenytoin, carbamazepine, chronic alcohol excess, St John’s Wort)
  • Malnourished patients (e.g. anorexia nervosa)
29
Q

Features of Quinine Toxicity

A

Classical hallmarks:
- tinnitus
- visual blurring
- flushed and dry skin
- abdominal pain

  • Prolonged QT (blocks Na and K channels)
    => risk of ventricular tachyarrhythmias
  • Hypoglycaemia (stimulates pancreatic insulin secretion)
  • Pulmonary oedema
30
Q

Management of quinine toxicity

A

Supportive:
- IVF
- inotropes
- Bicarb
- Positive pressure ventilation if pulmonary oedema

31
Q

Describe the appearance on a blood gas when a patient has taken a salicylate overdose

A

Mixed respiratory alkalosis and metabolic acidosis.

  • Early stimulation of respiratory centre = respiratory alkalosis
  • later the direct acid effects of salicylates + acute renal failure) lead to an acidosis
  • In children metabolic acidosis tends to predominate.
32
Q

Features of salicylate overdose

A
  • Hyperventilation
  • tinnitus
  • lethargy
  • sweating, pyrexia
  • nausea/vomiting
  • hyper/hypoglycaemia
  • seizures
33
Q

Management of salicylate overdose

A
  • ABCDE
  • IV bicarb
  • Haemodialysis
34
Q

Indications for haemodialysis in salicylate overdose

A
  • serum conc. > 700mg/L
  • metabolic acidosis resistant to treatment
  • acute renal failure
  • pulmonary oedema
  • seizures
35
Q

Features of tricyclic overdose

A

ANTICHOLINERGIC:
- dry mouth
- dilated pupils
- agitation
- sinus tachycardia
- blurred vision.

severe poisoning:
- arrhythmias
- seizures
- metabolic acidosis

36
Q

Common ECG changes in Tricyclic overdose

A
  • sinus tachycardia
  • widening of QRS
  • prolongation of QT interval

QRS > 100ms= risk of seizures QRS > 160ms = ventricular arrhythmias

37
Q

Management of tricyclic overdose

A
  • IV bicarbonate
    first-line therapy for hypotension or arrhythmias
    indications
  • IV lipid emulsion is increasingly used to bind free drug and reduce toxicity
38
Q

What can precipitate lithium toxicity?

A
  • dehydration
  • renal failure
  • diuretics (especially thiazides)
  • ACEi/ARB
  • NSAIDs
  • Metronidazole
39
Q

Features of lithium toxicity

A
  • coarse tremor
  • hyperreflexia
  • acute confusion
  • polyuria
  • seizure
40
Q

Management of lithium toxicity

A

Mild-mod toxicity - normal saline

Severe - Haemodialysis

MRCP Pharmacology (22 decks)

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