Lecture 15: Poisons and Poisonings Flashcards
Types of Poisoning
Acute overdose
Chronic Exposure
Overall Poisoning diagnosis
- Physical diagnosis
a. eyes
b. skin
c. odour - Clinical Diagnosis
a. blood
b. urine
Diagnosis history
patients rarely lie (trust them if they have taken an overdose)
But may be unreliable, due to sedation and amnesic drug effects
- therefore the information you do get will tend to be accurate, but may only be a little bit and that will be all you have to rely upon
Physical diagnosis involving the eyes
Constricted pupils
Dilated pupils
Substances causing constricted pupils
- opiates (morphine) (has a central action on medulla causing capillary constriction)
- clonidine (is an antihypertensive medication, lowering central BP causing constriction of pupils)
- anti-cholesterases (neostigmine) (blocks ACh breakdown, causing increased circulation of ACh which has a local effect on the eye)
Substances causing dilated pupils
- Atropine (from plant atropabelladonna, “beautiful woman”. blocks muscarinic receptors
- Tricyclic antidepressants (antidepressants) (anticholinergic overdose causing constriction)
- amphetamine/MDMA (ecstasy) and BZP (party pills) (SNS stimulation causing NE release causing large pupils. psychedelic properties)
Physical diagnosis involving skin
- Sweating:
- increase w. amphetamine (increased SNS)
- decreased w. atropine (cholinergic) - Bullae (large blister):
- CO carbon monoxide (hypoxia damages the skin causes the blister)
- barbiturates
Physical diagnosis involving smelling odour
Odour
1. Ethanol (specific to the drink, beer > vodka)
2. Garlic
- arsenic
- organophosphates (anticholesterases) e.g. insecticides from farms
3. almonds (cyanide)
- contained within their stones. cyanide also found in some related stone fruits
Note: James bond: not instant kill like movies. cyanide blocks the use of O2 in body, therefore need to wait until the O2 already present in the body before death.
Clinical chemistry diagnosis via blood sample
Blood: (toxic levels)
- salicylate (component of aspirin/acetyle salicylate)
- paracetamol
- ethanol
- CO carbon monoxide (measured directly via looking at Hb levels)
- tricyclic antidepressants
- digoxin
- theophylline
Clinical chemistry diagnosis via urine sample
Urine: (toxic levels)
- salicylate
- opiods
- tricyclic antidepressants
Differences b/w using blood and urine samples
things are concentrated in the urine therefore can sometimes be easier to measure
additionally more easily available lab equipment for urine testing
Components of general supportive reatment
A Airway
B Breathing
C Circulation
Methods to Decreases absorption of the poison
- Emesis (vomit to get rid of drugs): syrup of ipecac
- Gastric cleavage (stomach pump, to try get tablets/capsules out of the stomach that haven’t yet dissolved)
- must have reflexes (to ensure goes down into correct place)
- not for corrosives/hydrocarbons
Note: not that effective and can cause damage/split the trachea and lungs - Activated charcoal IMPORTANT (50g every 4 hours)
- Fullers Earth (white clay) (or activated charcoal): Paraquat (herbicide)
Activated charcoal
Manner of decreasing absorption of a poison
- easy to use
- not noxious
- works well for many poisons/drug overdoses
- activated charcoal is sticky therefore binds the drug in the gut, reducing the amount of drug available for absorption
Paraquat
Herbicide
-rarely effective
- can cause poisoning with a small amount
- damages lungs by stimulating pulmonary fibrosis
Treatment: activated charcoal or fullers earth (white clay): both bind to the drug to decreased absorption in stomach
Methods to Increase elimination of the poison
- activated charcoal: enteral dialysis
- molecule crosses a membrane and is bound by activated charcoal on other side
- causes high conc of drug in blood and low in gut –> molecule travels in other direction down concentration gradient furthering clearance - haemoperfusion (invasive canular insertion therefore only used in severe overdoses. into arterial supply and then placed back into vein):
- charcoal (theophylline)
- ion exchange (salicylate) - haemodiaslysis (good for water soluble drugs. venous and renal dialysis)
- methanol (wood alcohol) (assoc. with blindness)
- ethylene glycol (antifreeze) (poisons kidneys) - Diuresis (has complications surrounding excessive ion and water loss, therefore not always used)
Effectiveness of Haemoperfusion with activated charcoal
very effective
adverse effects: platelet stick to columns –> platelet deficiency –> increased risk of bleeding
Specific antidotes to drug poisoning
- N-acetyl-cyteine treament (for paracetamol overdose)
- Naloxone (for morphine overdose) - ventilator and wait to metabolise drug
- Flumazenil (for bencodiazepine overdose) - ventilator and wait to metabolise drug
- Ethanol (for methanol overdose)
- Chelation
- Atropine/pralidoxime ( for anticholesterolases) e.g. insecticides
- Antibody
Antidote: N-acetyl-cyteine treatment
for paracetamol overdose
relatively specific
binds to the toxic paracetamol metabolite which causes the actual liver damage
Antidote: Naloxone treatment
for morphine overdose
specific and competitive antagonist of opiods (e.g. morphine) and hence reverses their effects
Note: has a short half life (1min), therefore is often used as a diagnostic agent, rather than treatment agent
- if wakes up and responds for a couple of minutes, then know that the overdose was at least partially due to morphine
Antidote: Flumazenil treatment
for bencodiazepine overdose
competitive antagonist for benzoasapine reversing its effects
Note: has a short half life (1min), therefore is often used as a diagnostic agent, rather than treatment agent
- if wakes up and responds for a couple of minutes, then know that the overdose was at least partially due to benzoasapine
Antidote: Ethanol treatment
ethanol and methanol are both metabolised by alcohol dehydrogenase
therefore if have methanol overdose, if you give high enough concentration of ethanol, will compete for metabolisation with methanol, and will decreased metabolisation of methanol to form its toxic metabolite (formaldehyde)
Instead of being metabolised, Methanol is rather eliminated via other routes such as urine and breath, which dont form formaldehye –> leading to an overall decrease in methanol assoc. toxicity
