Drug overdose (PSY) Flashcards
What is the maximum recommended dose of paracetamol?
2 x 500mg tablets, 4x in 24 hours (2g in one day)
What are the two types of paracetamol overdose?
Acute OD or staggered OD
What organ does paracetamol overdose affect the most?
Liver - causes hepatotoxicity
NAPQI production (paracetamol metabolite) is hepatotoxic and metabolised using glutathione (impaired in alcohol use, HIV, p450 inducers and malnourished patients = more at risk)
Which patients are at increased risk of paracetamol overdose? (4)
- chronic alcohol use
- HIV
- p450 inducers (SCARS)
- malnourished patients e.g. anorexia
What is the most important prognostic indicator in paracetamol overdose?
Arterial pH <7.30 = poor prognosis
How may patients with paracetamol overdose initially present?
Asymptomatic or mild GI Sx, N&V over 24h
What are the clinical features of paracetamol overdose? (5)
- nausea & vomiting
- RUQ pain - right subcostal pain (hepatic necrosis –> encephalopathy, hypoglycaemia, AKI, haemorrhage, cerebral oedema, death)
- jaundice (may signify acute liver failure)
- hepatomegaly
- altered conscious level (if taken with opioids/alcohol)
What investigations do we do in paracetamol overdose? (4)
- serum paracetamol concentration (whether treated or not based on nomogram)
- LFTs (ALT may be high)
- PT may be prolonged
- ABG - pH<7.3 is bad
When are peak paracetamol levels in paracetamol overdose?
4 hours after ingestion –> wait 4h before treating with N-acetylcysteine
How do we manage paracetamol overdose?
- if ingestion <1h ago and not staggered - activated charcoal
- if ingestion <4h ago - wait until 4 hours to measure level then treat with N-acetylcysteine accordingly
- if ingestion 4-15h ago - take immediate level and treat with N-acetylcysteine accordingly
- if staggered overdose (over >1h time period) or ingestion >15h ago - give IV N-acetylcysteine
When would we give a liver transplant for paracetamol overdose?
If pH<7.3 more than 24 hours after ingestion
What is aspirin overdose also known as?
Salicylate toxicity
What does aspirin overdose lead to on ABG?
Mixed respiratory alkalosis (due to hyperventilation) and raised anion gap metabolic acidosis (due to toxicity and acute renal failure)
What organ does aspirin overdose affect?
Kidney - nephrotoxic
What are the clinical features of aspirin overdose? (10)
- tinnitus
- nausea and vomiting
- lethargy
- tachypnoea (hyperventilation)
- diaphoresis (sweating)
- hyperthermia
- agitation
- seizures
- respiratory depression
- coma (if severe)
What investigations do we do in aspirin overdose? (3)
- ABG - mixed respiratory alkalosis (with compensatory response –> dehydration and hypokalaemia) by stimulation of respiratory centre which triggers metabolic acidosis (HCO3 loss, uncoupling of oxidative phosphorylation, lactic acid build up)
- ECG - hypokalaemic changes
- salicylate levels - repeat every 2h until peak
How is aspirin overdose classified?
According to peak salicylate levels:
- mild <300mg/L
- moderate 300-700mg/L
- severe >700mg/L
How do we manage aspirin overdose? (3)
- sodium bicarbonate - alkalises urine to increase aspirin elimination
- activated charcoal - can be used within 1h of overdose
- haemodialysis - if pulmonary oedema and severe metabolic acidosis
What drugs are involved in opiate overdose? (4)
- codeine
- dimorphine
- fentanyl
- loperamide
What drugs is opiate overdose most commonly due to? (2)
- heroin
- morphine
What are some risk factors for opiate overdose? (3)
- renal impairment - cannot excrete drug
- mental health conditions
- alcoholics
What are the clinical features of opiate overdose? (9)
- pinpoint pupils (bilateral miosis)
- respiratory depression (bradypnoea)
- altered mental status
- constipation
- needle track marks
- rhinorrhoea
- N&V + anorexia
- drowsiness
- coma
What investigation do we do in opiate overdose?
Therapeutic trial of naloxone - may show reversal of overdose signs
How do we manage opiate overdose? (2)
- airway management and oxygen
- IV naloxone
What are the clinical features of TCA overdose?
- dry mouth and dry hot skin
- dilated pupils
- agitation
- blurred vision
- arrhythmias - prolonged QT interval and QRS widening
- convulsions
- altered mental status
What investigation do we do in TCA overdose?
ECG - wide QRS >100ms associated with seizures and >160ms with ventricular arrhythmias
How do we manage TCA overdose?
IV sodium bicarbonate
What are the clinical features of SSRI overdose? (10)
- N&V
- agitation
- tremor
- nystagmus
- drowsiness
- sinus tachycardia
- rhabdomyolysis
- convulsions
- renal failure
- coagulation deficiencies
What syndrome might be seen in SSRI overdose?
Serotonin syndrome - marked neuropsychiatric effects, autonomic instability and neuromuscular hyperactivity
What investigations do we do in SSRI overdose?
- 12 lead ECG, blood glucose and paracetamol concentration in deliberate self-poisoning
- cardiac monitoring and serial ECG if large citalopram/escitalopram ingestion, duration will depend on quantity
How do we manage SSRI overdose?
- serotonin syndrome –> titrated IV benzodiazepines
- seizures –> benzodiazepines
- cardiac monitoring if large citalopram or escitalopram ingestion
- observation for 12h is recommended based on the pharmacokinetics of the individual SSRIs
How do we manage sedative/hypnotics overdose? (3)
- ABCDE assessment
- supportive care
- flumazenil - only by trained clinician, or active charcoal (if significant harm)
What are the clinical features of beta-blocker overdose?
- light-headedness or syncope due to bradycardia or hypotension
- HF can be exacerbated/precipitated
- sotalol –> VT
- propranolol –> coma and convulsions
How do we manage beta-blocker overdose? (2)
- if bradycardia –> atropine
- if resistant to atropine –> glucagon
What kind of symptoms do different types of CCB overdoses cause?
- dihydropyridine CCBs –> profound peripheral vasodilation and severe hypotension
- verapamil and diltiazem –> arrhythmias (including complete heart block and asystole)
How do we manage CCB overdose?
IV calcium, high doses of catecholamines, insulin and glucagon (and levosimendan if severe)
How can we generally screen for overdose?
Toxicology screen
