Drug Overdose (Paracetamol, Opiates, Benzos, TCAs & SSRIs) Flashcards
1
Q
What is the pathophysiology behind salicylate (aspirin) poisoning?
A
- Pathophysiology
- Usually aspirin.
- Uncouples oxidative phosphorylation causing metabolic acidosis.
- Also directly stimulates CNS respiratory centre causing ↑RR and respiratory alkalosis.
2
Q
What are the common signs and symptoms of salicylate poisoning?
A
- ASA-DOSE:
- Agitation or delirium.
- Sweating
- Auditory symptoms: tinnitus or deafness.
- Dizziness
- Overbreathing: ↑RR due to CNS effect or response to metabolic acidosis.
- Seizures and coma.
- Emesis
3
Q
Which investigations should be done in suspected salicylate poisoning?
A
- Investigations
- Plasma salicylate levels. Repeat every 2 hours until it peaks, which can take up to 6 hours.
- U+E: ↓K+, AKI if severe.
- ↓Glucose
- ABG and HCO3-: initially alkalosis, later acidosis.
4
Q
How is salicylate poisoning managed?
A
- ABCD:
- Activated charcoal ± MDAC.
- Sodium Bicarb for urine and serum alkalinisation: ionises salicylates so they can’t cross blood-brain barrier, and can’t escape renal tubules so are eliminated from circulation.
- Correct glucose and K+ deficits.
- Dialysis if: ↓pH, ↑↑salicylates, AKI.
5
Q
What is the background of TCA poisoning?
A
- TCA overdoses are rare – as the drug is not widely used now – but very dangerous.
- In contrast, SSRI overdoses are commoner, but much less likely to be fatal.
6
Q
What signs and symptoms might be seen in TCA overdose? What effects are these symptoms due to?
A
- Anticholinergic effects:
- Hot dry skin.
- Mydriasis: dilated pupils.
- ↑HR
- Urinary retention.
- Agitation and delirium.
- Neurological: seizures, coma, hypertonia, hyperreflexia.
- Anti Na+ channel effects:
- Arrhythmias, including VT and VF.
- Cardiac arrest.
- Heart block.
- Anti α-adrenergic effects:
- ↓BP
7
Q
Which investigations should be performed in TCA overdose?
A
- ECG: wide QRS, long QT, increased PR. Continue to monitor if large OD or initial abnormality found.
- U+E
- Glucose
- ABG: metabolic acidosis secondary to seizures and/or tissue hypoxia from ↓cardiac output.
8
Q
How can TCA overdose be managed?
A
- Activated charcoal (± MDAC) if <2h since ingestion.
- Sodium bicarbonate to reverse Na+ channel blockade if QRS >100 ms or there is ventricular arrhythmia.
- DC cardioversion, lidocaine, or MgSO4 if bicarb fails. Most other anti-arrhythmic drugs are contraindicated.
- Benzodiazepines if there are seizures.
- Lipid emulsion if peri-arrest.
9
Q
What are the signs and symptoms of benzodiazepine poisoning?
A
- Drowsy. In severe cases, coma.
- Neurological impairment, including motor impairment, diplopia, slurred speech, and ataxia.
- Anterograde amnesia.
- Rarely, paradoxical symptoms: anxiety, delirium.
- ↓RR, which would suggest a combined OD.
10
Q
How is benzodiazepine poisoning managed?
A
- Supportive treatment, especially airway.
- Activated charcoal only if BZD taken in combo with something else.
- Flumazenil is the antidote.
11
Q
What are the indications for giving flumazenil? How does it work and how is it given?
A
Mechanism:
* BZD receptor antagonist, which mainly acts to reverse CNS depression.
- Indications:
- Severe OD – with marked impairment of consciousness or respiratory distress – in a first time or infrequent user.
- In practice, it is most likely to be used for iatrogenic overdoses, when we can be sure that they are not long-term users and it is not a mixed overdose.
- Contraindications due to seizure risk:
- BZD-dependant patients.
- Mixed TCA OD.
- Epilepsy history.
- Dose and administration:
- Use the minimum effective dose.
- Apply ECG monitoring when giving flumazenil as it may unmask an arrhythmia, especially if patient on TCA or carbamazepine.
- Half life is less than BZD, so may wear off first.
12
Q
What are the signs and symptoms of iron poisoning?
A
- Signs and symptoms
- Early (0-6 hours): GI symptoms including nausea, vomiting, diarrhoea, and abdo pain.
- Delayed (2-72 hours): black stools, circulatory collapse, and CNS symptoms including drowsiness, seizures, and coma.
- Late (2-4 days): liver and kidney failure.
- Very late (2-5 weeks): gastric stricture.
13
Q
Which investigations should be done in suspected iron poisoning?
A
- Establish amount of elemental iron from history.
- Fe level, taken at least 4 hours after ingestion, then repeated 2-hourly.
- ↑WBC
- ↑Glucose
- U+E and LFT.
- Daily monitoring: clotting, HCO3-.
14
Q
How is iron poisoning managed?
A
- Gastric lavage.
- Desferrioxamine is the antidote.
- Desferrioxamine (aka deferoxamine)
- Chelates Fe, which is then excreted as red urine.
- Indicated in severe OD, characterized by ↓consciousness, seizures, shock, metabolic acidosis, GI bleed.
- Contraindicated in kidney failure.
- Can cause ↓BP and pulmonary oedema.
15
Q
What is the pathophysiology/background behind organophosphate poisoning?
A
- Relatively common suicide method in developing world, taken in the form of fertilizer. Also used as chemical weapon (sarin, VX).
- Percutaneous or oral entry → cholinesterase inhibition → ↑acetylcholine (ACh) levels → parasympathetic activation, NMJ depolarization, and CNS dysregulation.
