Overdose & illicit drug use Flashcards
How is an opiate overdose treated?
Ventilation
IV/IM/SC Naloxone every 2-3mins
How does Naloxone work?
Competitively binds to opioid receptors causing a blockade
What needs to be taken into account when giving Naloxone?
Half life is shorter than the half life of opioids
Can resuscitate a patient but will quickly relapse if not maintained
What are the signs &symptoms of an opioid overdose?
CNS and respiratory depression Miosis Apnoea Fresh needle/track marks RARE: Frothy pink sputum, seizures, pulmonary rales
How is an opioid overdose investigated?
ECG- may see prolonged QRS
Tox screen
CXR - ARDS
Why are tricyclics damaging in overdose?
Narrow therapeutic range
Become potent cardiovascular and central nervous system toxins in moderate doses.
What receptors do tricyclics act on?
- Anticholinergic effects at muscarinic receptors
- Alpha-1 adrenergic receptor antagonism (vasoD)
- Fast Na channel blockade in cardiac cells (impaired CO & hypoT)
- Inhibition of pre-synaptic reuptake at terminals of norE/norA, serotonin, and dopamine
- Competitive antagonism of H1 and H2 receptors.
- Absorbed by the GI tract & peak at 2-8hrs
- Metabolised by the liver
What are the signs & symptoms of a tricyclic overdose?
CNS: delirium, lethargy, seizure, and coma, HypoT, arrhythmia, metabolic acidosis
Anticholinergic: Dry mouth, VasoD pupils, blurred vision, Tachy, agitation
Features of serotonin syndrome
Cerebellar signs: Ataxia, myoclonic movements, Inc muscle tone, hyperreflexia, extensor plantar responses
How is tricyclic overdose treated?
GI decontamination QRS >100/arrhythmia= sodium bicarb, ICU IV Lipid emulsion hypoT= vasopressors (NorA)/glucagon hyperV for cardiotoxicity Seizures: Benzos
How can risk of overdose be assessed?
- Suicide & depression risk
- Alcohol use
- Intent
- Did they want to die?
- Did they leave a note?
- Done in a place where they wouldn’t be found
- Was it planned? (giving away possessions)
- Stockpiling tablets
- Regret decision or want to try again?
How is a tricyclic overdose investigated?
ECG: Sinus Tachy, Prolonged QRS, R wave, prolonged QT
Blood tests
How is paracetamol metabolised? What is different in overdose?
Metabolised in the liver via 2 pathways
1) Glucuronidation: 60% of metabolism
2) Sulfation: 30% of metabolism
Breakdown
Partical breakdown by cytochrome P450 to a potentially toxic intermediate metabolite NAPQI
Normal conditions NAPQI combines w/intracellular glutathione = non-toxic mercapturate derivative
Metabolites excreted in the urine
In overdose minor cytochrome P450 pathway becomes dominant = inc NAPQI too much to detoxify
Excess binds to cellular components causing mitochondrial injury & hepatocyte death= acute liver failure
What are the signs & symptoms of a paracetamol overdose?
Asymptomatic until 24-72hours when acute liver failure occurs
N&V
Hepatic necrosis: Jaundice, RUQ pain, encephalopathy, hypoG
Renal failure
Metabolic acidosis
Oligouria
How is a paracetamol overdose investigated?
Paracetamol & salicylate levels: Only accurate >4hours after ingestion
LFTs
Glucose
U&Es
Prothrombin & INR: Indicator of acute liver failure
ABG: Acidosis
Commence Paracetamol treatment graph
How is a paracetamol overdose managed?
<8hours: Activated Charcoal if 150mg/kg ingested within the hour, IV Acetylcysteine & anti-emetic (Ondansetron)
>8hours: IV Acetylcysteine w/5% Dextrose
>24hours: Evaluate for liver transplant
Acetylcysteine given in 3 divided IV doses over 21hours
