Drugs, overdose and Poisoning Flashcards
Epidemiology of Poisoning
4.3million/yr in US – 90% at home
Common cause of female admission
Increased suicide risk in year after - large proportion of admissions are for children under 6
What is a poison?
All substances are poisons depending on dose
A substance can also become a poison by an inappropriate route of adminstration or by side effects or interactions with another drug
Common agents used in poisoning (7)
Paracetamol Carbon monoxide
Aspirin Beta blockers
Antidepressants Street drugs
Iron
Presentations of poisoning
Widely vary - some patient will be more vulnerable than others
Any patient with an altered level of consciousness, young person with a life threatening arrhythmia or a puzzling presentation should be suspected
Principles of treatment of poisoning (5)
Prevent further absorption Enhance elimination of the poison Manage side effects Support vital functions Use of antidotes if there are any
Preventing further absorption
Gastric decontamination - washout, Ipecac, gastric lavage or activated charcoal
Drug absorbing agents
Whole bowel irrigation
Enhancing elimination
Diuresis
Urine acidity manipulation - for salicylates & herbicides
Haemofiltration/Dialysis- for salicylate, alcohol, Lithium,
Antidotes
Must be Drug specific and dose related. Some drugs have specific antidotes: opiates, paracetamol, digoxin etc
Toxidromes
A body wide syndrome due to high levels of toxins
They generally fall into six types but there is variation
Anticholinergic, sympathomimetic, Opiate, sedative, Cholinergic, hallucinogenic
Anticholinergic toxidrome
‘blind as a bat (blurred vision/dilated pupils), mad as a hatter(coma, hallucination, psychosis), red as a beet (flushing), hot as hell (fever), dry as a bone (dry skin), bowel and bladder (ileus, decreased bowel sounds & urinary retention) lose their tone and the heart runs alone (tachycardia)’
Sympathomimetic toxidrome
Anxiety, delusions, hyperreflexia, paranoia, piloerection, sweating and seizures. Pupils dilates and sweating. BP, HR and RR increase. Increased bowel sounds
Opiate toxidrome
Coma, pinpoint pupils and respiratory depression
May also have shock, pulmonary oedema, bradycardia, hypothermia, hypotension, Caused by opiates
Cholinergic toxidrome
Killer ‘B’s –> bronchospasm & bronchorrhoea
SLUDGE - salivation, lacrimation, urination, diarrhoea, gastrointestinal distress and emesis
Pupils will be pinpoint and bradycardia, may have seizures
Causes of an Anticholinergic toxidrome
Antidepressants, antipsychotics, antiparkinsonian drugs, antihistamines
Also atropine, benztropine, datura, scopolamine
Causes of an Cholinergic toxidrome
Caramates, mushrooms and organophosphates
Also nerve gases
Causes of an Sympathomimetic toxidrome
Salbutamol, cocaine, ephedrine, amphetamines, meth
Sedative toxidrome (aaccdd)
Ataxia, coma, confusion, delirium and general deterioration of CNS functions. possible apnea,
Causes of an Sedative toxidrome
Anticonvulsants, barbiturates, benzodiapzepines, GABA, GHB, methaqualone and ethanol
Generally anticonvulsant but GHB and methaqualone can cuase paradoxical seizures
Hallucinogenic toxidrome
Disorientation, hallucination, panic, increased bowel sounds, seizures. May lead to raised HR, BP and RR
Causes of an Hallucinogenic toxidrome
Some amphetamines, cocaine and phencyclidine
Algorithm for identifying toxidromes
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Paracetamol
Toxic metabolite is glutathated in liver –> quickly runs out
Leads to hepatototicity and risk of death
One of the most common poisonings and commonest cause of acute liver failure
Often asymptomatic in first 12-24hrs with N&V only
Carbon monoxide
Binds to Hb with great affinity causing cellular hypoxia
100% or hyperbaric O2 displaces CO
Severity is indicated by level of COHb
Iron
Causes gastrointestinal damage –> mucosal sloughing and haemorrhage
Can cause Hypotension.
Treat with desferrioxamine (a chelating agent)
Antidepressants
Tend to cause arrhythmias, siezures and coma
Have a prolonged action so require longer term care
Drugs of abuse overdose
Give general support
Use sedation if anxious or delirious
Use beta blockers for tachyarrhythmias
Can cause drowiness, convulsions and hyperprexia
Psychiatric care
Full assessment of suicidal risk and additional evaluation for any secondary or ongoing risk factors
Illegal drug use
Rapid growth in consumption –> younger people are using drugs and many use them with little negative consequence
Drugs of abuse
Stimulants –> cocaine, crack, amphetamine, Khat
Opiates –> heroin, methadone, DF118’s, Over the counter
Benzodiazepines, cannabis, tobacco, alcohol
Clubber drugs–>MDMA, ketamine,
Stimulants
Increase energy, feelings of power and sex
Issues in south london with crack
Work from the late 90’s on increasing engagement with users
Increase in afro-caribbean clients in the services to reflect the population
Crack Cocaine
White stones/rocks –> £10-20 per rock
smoked or injected –> mix with heroin IV (speed-balling)
Risks of debt, crime, violence, sex work, psychosis, dependance, CVS diseases, homelessness
Heroin
Called ‘brown’ or ‘smack’ –> £40-60/g (0.4g referred to as 1/4 or 1/16th of an oz= 1.3/4g
Gives a powerful rush and dulls physical or emotional pain
Injected or smoked (chasing the dragon)
Risks of heroin/opiate use
Infection —> HIV, HCV, HCB, septicemia
Overdose, DVT, Dependance, Debt, crime and prostitution
Abuse of Benzodiapzepines
Limit to short course to prevent dependence
Have street value & increased risk if mixed with alcohol or opiates
Treat dependence with a switch to diazepam and then a slow reduction
Offer counselling and support
Cannabis
Hash, resin, ganga, dope, weed, Blow, skunk
THC is active ingredient
Smoked in joints, pipes or bongs –> £50-80/oz, 1/8th for £15
Can cause anxiety, paranoia, psychosis,
Clubber’s drugs
Ecstacy, ketamine, cocaine, amphetamines, cannabis
All carry risks of OD, misadventure and mixing with other drugs
Alcohol
Binge drinking is a growing problem - particularly in women
Increases the risk of OD if mixed with benzos/opiates
Can cause depression, anxiety or suicidality
Aspirin
An acidic drug which in overdose can cause tinnitus and long term middle ear problems
Treat with diuresis or usually haemodialysis
Careful as there is lots of salicylate in wintergreen oil
Beta-blocker overdose
Can cause bradycardia (treat with atropine) hypotension and complete heart block
Glucagon is an effective antidote
Activated Charcoal
Used to decontaminate the bowel and prevent further absorption. Poor at absorbing: Iron, ethanol, methanol, ethylene glycol, acids and alkalis, metals (Fe or Li)
Good for absorbing: Carbamazepine, Theophylline, Quinine, Phenobarbitone
Types of poison exposure
Accidental - most common for children
Mainly >12yr and female, suicide/parasuicide or illicit drug use/overdose. 80-100,000 AnE attendances/yr and 1500 deaths/yr
Guy’s specialist poisoning unit
2/3 of calls from AnE departments, mainly from nurses
In 70% of causes the agents ingested were pharmacuticals, next being industrial chemicals at 13%
Most common –> Paracetamol, ibuprofen and aspirin
How common is paracetamol poisoning?
Common 50% of self-admission with poisoning in UK is paracetamol - 48,000 OD cases per year - 150 deaths/yr
Treatment of paracetamol poisoning
N-acetylcysteine (NAC) is 99% effective if given in 8-10hrs
delayed presentations or multiple doses - less effective
What determines the toxicity of paracetamol overdose?
Time between ingestion and treatment
Dose - toxic above 150mg/kg or 75mg/kg in high risk pts
Risk factors –> decreased glutathione (malnutrition, HIV, anorexia) or induction of P450s (alcoholics, TB drugs, anti -epileptics)
Hepatic processing of Paracetamol
90% is conjugated by P450s
5% renally eliminated
5% metabolised into toxic NAPQI - if not detoxified by glutathione it binds to hepatic proteins causing cell death
Aspirin Poisioning
Less common now but still happens. Severity depends on dose: 150mg/kg - mild, 250mg/kg - moderate, 500mg/kg - severe/fatal
Children and the elderly at a greater risk
Symptoms of Aspirin Poisoning
Mild to moderate –> vomiting, tinnitus, sweating, hyperventilation and respiratory alkalosis
Severe –> Acute renal failure, pulmonary oedema, CNS features (agitation, confusion, coma, convulsions), metabolic acidosis is a bad prognostic sign as it allows increased salicylate into the CNS
Symptoms of NSAID overdose
Ibuprofen and mefenamic acid most commonly taken in OD
Vomiting, diarrhoea and abdominal pain
Seizures in 5% of cases with ibuprofen and 20% with mefenamic acid
Very large doses can cause metabolic acidosis, renal failure and CNS depression
Benzodiazepine overdose
Common, OD of just benzos is generally fine (drowsiness, ataxia, dysarthria, confusion)
More severe cases do happen, especially if drugs were mixed or in elderly patients –> coma, resp depression & hypotension
Treatment of Benzodiazepine overdose
Flumazenil is a benzodiazepine antagonist which can be used in severe cases but should not be used routinely as it can cause arrhyhmias and convulsions (particularly if patient has Hx or taken other drugs which increase the risk of them)
Usually supportive care is all that is needed
How common is antidepressant overdose?
Can be SSRIs or Tricyclics - overdose is responsible for 1/10 suicides
Common as 60-70% of suicides are depressed and 1/3 of depressed people are given antidepressants
Tricyclic antidepressant overdose
Pharmacologically dirty drugs - can cause severe toxicity
10-20mg/kg is life threatening
TCA’s include Dothiepin
Clinical features of Tricyclic antidepressant overdose
Rapid onset (1/2hr) - anticholinergic effects (dilated pupils, blurred vision, hot+dry skin, urinary retention, hyperreflexia, delirium, myoclonic jerks)
CVS - broad QRS, VT arrhythmia & cardiac arrest, hypotension
CNS - Drowsiness, coma, resp depression, convulsions, hypertonia
SSRI overdoses
Clean pharmacologically and better tolerated in overdose
Usually cause N&V and dizziness, if >1500mg taken CNS depression and seizures can occur
Symptoms of untreated paracetamol overdose
Will present late with jaudice, encephalopathy & coagulopathy
Can develop renal failure, metabolic acidosis, hypotension and cerebral oedema
Criteria for giving NAC
Give NAC if concentration is at or over line
At 4hrs –> 200mg/L or 100mg/L in high risk patient
At 8hrs –> 100mg/L or 50mg/L in high risk patients
Relative Antidepressant toxicities
TCA’s - 34 Lithium - 15 MAOI’s - 14 Atypical’s - 6 SSRI’s - 2 (Numbers are deaths/million prescriptions)
Lead poisoning
Can present with abdominal pain, peripheral motor neuropathy, fatigue, constipation. can also have blue lines on the gums (20% of adults but very rare in children). Blood lead >10mcg/dL and microcytic anaemia with basophilic stippling. Treat with EDTA, D-penicillamine, DMSA. can be caused by Pica (paint)
Digoxin poisoning
Used for rate control in AF but can also be used for symptomatic improvement in HF. toxicity risk increases from 1.5-3mcg/L. Can be brought on by hyperkalaemia, renal failure, MI, acidosis/metabolic disturbance, hypthermia or other drugs. Presents with lethargy,N&V, anorexia, confusion, yellow-green vision and arrhythmias (AV block or bradycardia)
Treatment of Digoxin toxicity
Digibind
Treat and correct arrhythmias
Monitor potassium
Opiate overdose
Causes respiratory depression and pinpoint pupils
Treat with naloxone but careful as this acutely induces withdrawal which is dangerous in addicts
Features which potentiate warfarin
Liver disease
P450 inhibitors - amiodarone, ciprofloxacin, isonizaid etc
Cranberry juice
Drugs which displace warfarin from albumin (NSAIDs)
Or drugs which inhibit platelet function (NSAIDs again).
Treatment of amitriptyline (and other tricyclic) overdose
IV bicarbonate to treat cardiac issues
Treatment of benzodiazepine overdose
Flumazenil
