Poisoning and Antidotes Flashcards
How many admissions yearly for self-poisoning in England and Wales
160k
How many adults conscious on arrival to hospital after self-poisoning
80%
Who is more likely to take an overdose
Females
Who is more likely to be successful in suicide
Males using measures that don’t involve medication
Define poisoning
Exposure to a drug, chemical, pollutant in enough quanitity to produce an adverse effect
Can be acute or chronic
How many cases of poisoning are accidental
almost 50%
Percentages of poisoning at home, workplace and related to oral adminsitration
90%
5%
90%
How many cases of poisoning are deliberate
25%
How many cases of poisoning are due to therapeutic error
20%
Examples of accidental poisoning
Children e.g. household chemicals and parents medications
Duplication of therapy
Confusion over doses
Prescribing or dispensing errors
Counterfeit drugs that may contain harmful ingredients of contaminants
Examples of deliberate poisoning
Deliberate poisoning is when you poison others to cause harm
Overtaking medicines for beenfits e.g. thyroxine for weight loss
Drug misuse, self-harm and suicide
What is the case in most scenarios when there is deliberate poisoning: adminsitration, how many drugs, most commonly implicated 2nd agent
Self administration of a prescribed or OTC medicine or illicit drug
Most patients have taken 1+ drug, alcohol is the most commonly implicated 2nd agent
What is occupational poisoning
Chemicals found in place of work e.g. Xrays, lead, mercury, asbestos, pesticides, solvents, corrosive agents, fertilisers, snake bites
What is environmental poisoning
e.g. air, water, soil pollution
CO poisoning from dodgy boilet in rented properties is common
Stats for CO poisoning
50 deaths/year
4k medical visits for CO exposure
Poisoning in pregnancy
Unborn child can be very vulnerable to the effects of drugs and chemials
Lots of teratogenic medicines e.g. isotretinoin, valproate, alcohol etc
Also environmental poisoning
Majory of poisons reported are due to…
Poisons
Top 3 common drugs taken in overdose and stats
Paracetamol (~170k/year reported on ToxBase)
Ibuprofen (~55k/year)
Codeine (~40k/year)
Nicotine poisoning
Highly toxic by ingestion, inhalation and skin contact
As little as 40mg nicotine can be fatal in adults
Small amounts can be life threatening
Vapes can be appealing to children - sweet smell, colours etc
Increased no. of people being admitted to hospital from vaping
Signs of nicotine toxicity
Nicotine is a stimulant
Sympathomimetic drug - released dopamine
Large amounts = increased HR, contractility, BP and massive release of dopamine
SE of nicotine
Dizziness, headache, sleep disturbances, irritability
Tachycardia, increased or decreased HR, increased BP, CAD
Nausea, dry mouth, dyspepsia, diarrhoea, heartburn
What is the EU tobacco product directive 2014
A lot more regulation around vapes to reduce incidence of hospital admissions
Must be >18 to buy
No advertising on TV, radio, newspapers/magazine
Only can advertise at point of sale or local advertising
Consumer product = max 20mg/ml nicotine allowed to be sold
>20mg/ml needs to have medicinal license
Max quantitiy 10ml (refill contianer) or 2ml (cigarette, cartridge)
Must be child resistant
What age does most poisoning occur in children
<5
Poisonous substances found in accessible cupboards, medicines can look similar to sweets
Top 3 substances ingested by childen </5
Paracetamol
Ibuprofen
Multivitamins
Most common household poisons
Fabric cleaning liquid tablets, diffusers, bleach, air fresheners, disinfectants
Batteries
Post major risk to children and toddlers
Can cause serious damage in just a short time
Pharmacist role in preventing self-poisoning - paracetamol
Reduction of paracetamol pack sizes, 1998
32 OTC, 16 GSL
Led to large reduction in number of poisoning and reduction in number of people needing liver transplant
Maximum 100 paracetamol can be sold at any one time in a pharmacy
Supermarkets can sell up to 32 capsules/tablets
Use professional judgement to decide appropriate quantity to supply and what limits to impose
Pharmacist role in preventing self poisoning - general
Child resistant drug containers and safe storage of medicines
Medication reviews
Patients understanding the dose of medicine the maximum daily dose
Disposal of expired and unused medicines
Monitoring of sale/sipply of medicines subject to abuse
Ensure quality of imported products
Pharmacist role in treatment of poisoning
Recognise poisoning has occured
Establish a patient’s drug history
ID any agents involved
Give advice on antidote use - posions unit/TOXBASE
Ensure availability of appropriate antidotes
Provide patient info
Things to ask e.g. if a child is taken into A&E by a parent who finds them playing with a handful of small white tablets
Ask what the tablets could be - what medication is in the house
If she has the tablets, look for at characteristics: marking, size, shape, score down the middle etc
Has the child actually taken any
Do you know how many they have taken
Child’s symptoms
Can the child communicate
Identify tablets
Treat the symptoms
Tictac is a database that can help medications - may give you one or a list of medicines it vcould be, then work out it could be from there by asking Qs
Management of posioning
Some may be managed in primary care
Hospital admission criteria - potentially life threatening or delayed action poisons, self-harm/deliberate poisoning
Most management is symptomatic, continuous assessment and monitoring
Psychiatric/social assessment - accidental or intentional poisoning/self harm
Patient often rescuscitated first before identification of agents ingested
Define toxidrome
Group of symptoms used to identify agents
Classic toxidrome for opioid overdose and anticholinergics
Opioid overdose: unconscious, hypertension, respitatory depression, pinpoint pupils
Anticholinergic: dilated pupils, dry mucous membrane, urinary retention, tachycardia
3 types of specific treatment for poisoning
Gut decontamination to stop medication being absorbed
Enhanced elimination
Antidotes
Gut decontamination - activated charcoal
Absorbs ingested substances preventing their absorption into systemic circulation
Must be fully conscious or have a protected airway
Will only work up to the point that medicines are absorbed
Most drugs absorbed 20 mins - 1 hour from ingestion so if OD was 3 hours ago, there is no point giving charcoal
Activated charcoal is ideal up to 1 hour, max 2 hours
Gut decontamination - whole bowel irrigaiton e.g. polyetheylene glycol
Cleanses the entire bowel through enteral administration of large amounts of an osmotically balanced solution like polyethelyene glycol
Used for high doses of iron, lithium
Enhanced elimination with urinary alkalisation
e.g. NAHCO3
Increases eliminaiton of weak acids like aspirin
Administration titrated against urinary pH
Try keep urinary pH between 7.5-8.6 to prevent aspirin being ionised and reabsorbed in renal tubules
Blood gases and K levels must be measured
Enhanced elimination with haemodialysis/hemoperfusion
Remove blood and put it back in
Only used for a limited subset of drugs/chemicals e.g. severe aspirin, lithium, ethylene glycol, methanol
Antidotes and their mechanisms
Substances that can counteract a form of poisoning by a variety of mechanisms:
- forming an inert complex with the poison
- accelerating detoxification of poision
- reducing rate of conversion of the poison to a more toxic compound
- competing with the poison for essential receptor sites
- blocking essential receptors through which the toxic effects are mediated
- bypassing the effect of the poison
What is used for digoxin toxicity
Digi-fab
What is digi-fab
Used for digoxin toxicity
Forms an inert complex with digoxin and it is no longer toxic and will be excreted to the body
Binds in a 1:1 ratio - need to work out how much a patient has taken, and from that work out how much Digi-fab to give
Digoxin is a potent inhibitor of Na/K-ATPase to toxicity will result in strong inhibition of it = increased intracellular sodium = increased intracellular calcium = increased conttacility and tachycardia
N-acetylcysteine (NAC) for paracetamol
Normal therapeutic dose: ~95% metabolised via glucuronide mechanism and forms a conjugate which is excreted in urine, only ~5% forms the toxic NAPQI metabolite
When too much paracetamol is taken, the other pathway become satruated meaning a lot more of the paracetamol is metabolised ot the toxic ANPQI, causing hepatoxicity
NAC replenishes gutathione to accelerate detoxiifcaiton of paracetamol
- does this by metabolising to glutathione
- the glutahtione will bind to NAPQI to form to non-toxic metbaolites as well to force more through the other pathway
Ethylene glycol (anti-freeze) poisoning and antidote
- Metabolites of ethylene glycol are toxic
e.g. oxalic acid clogs renal microcirculation and acute tubular necrosis
e.g. formic acid causes damage to retina leading to blindness
e.g. glycolic acid causes metabolic acidosis - antidote: ethanol or fomepizole - reduces rate of conversion of ethylene glycol ot toxic metabolites
- either will give 40% alcohol or give femepizole (competitive antaognist, more expensive)
Naloxone for opioids like morphine, heroin, oxycodone
Direct inhibitor of opioid receptors
Has high affinity for opioid receptors in brain
Displaced opioid from the receptors and it will be metabolised and excreted from bodt
Has short half life so may need repeated doses or infusion depending on how much morphine was given to patient
Phytomenadione (Vitamin K) for warfarin
By passes effect of warfarin inhibiting VKOR
Warfarin commonly implicated in poisoning
When you give warfarin, it blocoks VKOR, stopping conversion of vit K to reduced vit K which is involved in clotting factors
Too much warfarin = not enough clotting factors = increased risk of bleeding and bruises
Give vitamin K to help regenerate the required clotting factors
Does not inhibit warfarin
