Foodborne diseases

Disease class: Poisoning

Also known as

• Food poisoning

 

This is a notifiable disease. This means that all diagnosed cases must be reported to the national Public Health services.

[Medical toxicology] Introduction

Medical toxicologists specialise in diseases caused by poisons.
This is a pathology discipline.
There is significant overlap with emergency medicine and poisoning cases are often seen in paediatrics.

 

Etymology

• Latin toxicum, toxicī = poison
• Ancient Greek λογία (logia) = study

Terminology

• Poison: a substance, which can severely harm an exposed organism.
• Toxin: a poison, which is produced within a living organism.
• Venom: a toxin, which is inserted into another organism, either predator or prey, with the intention of harming the victim.

History taking

 

Physical examination

 

Blog page: Poison database

 

Common diseases:

• Paracetamol overdose 
• Opioid overdose 
• Benzodiazepine overdose 
• Ethanol poisoning
• Tricyclic antidepressant overdose
• Salicylate poisoning 
• Iron poisoning
• Carbon monoxide poisoning
• MDMA poisoning
• Digoxin poisoning
• Methanol poisoning
• Ethylene glycol poisoning 
• Acetylcholinesterase inhibitor overdose

Urine drugs of abuse

Biochemistry homepage  

  

Clinical indications:

Screen for recent use of drugs of abuse. Seven drugs of abuse are included in the screen, these are:

1. Amphetamines / MDMA
2. Benzodiazepines
3. Cannabis (THC)
4. Cocaine
5. Methadone metabolite (EDDP)
6. Opiates
7. Heroin metabolite (6-AM)

 

Specimen type: 

• Urine

 

Sample type: 

• Random Urine

 

Turnaround time: 

• Inpatient: 6 hours 
• Outpatient: 24 hours 
• GP: 24 hours

Osteonecrosis

Disease class: Bone diseases

Also known as 

• Avascular necrosis 
• AVN

 

Pathophysiology

• Disruption of the normal vascular supply to bones can cause ischaemia and necrosis.

 

Causes

• Trauma (particularly bone fracture)
• Cancer
• Lupus
• Sickle cell disease
• HIV infection
• Gaucher’s disease
• Decompression sickness
• Heavy metal poisoning (e.g. lead and cadmium)
• Adverse drug reactions (e.g. corticosteroids, bevacizumab)

Types

• Osteonecrosis of the Jaw (associated with bisphosphonate treatment)
• Avascular necrosis of the femoral head
• Avascular necrosis of the knee
• Avascular necrosis of the ankle
• Avascular necrosis of the humeral head
• Avascular necrosis of the shoulder
• Avascular necrosis of the scaphoid
• Preiser's Disease: Avascular necrosis of the scaphoid without fracture
• Avascular necrosis of the spine 

Management 

• Arthroplasty
• Arthrodesis
• Revascularisation procedures (emerging field)

Lead poisoning

Back to toxicology

This refers to disease caused directly by exposure to the element lead (Pb, atomic number 82).

Routes of exposure

• Ingestion
• Inhalation
• Skin exposure

 

Symptoms

Acute poisoning

• Metallic taste 
• Abdominal pain
• Spasmodic abdominal pain (lead colic) 
• Vomiting
• Diarrhoea
• Drowsiness
• Anorexia
• Fatigue
• Muscle weakness
• Headache

Chronic poisoning

• Gastrointestinal disturbances
• Constipation 
• Weakness
• Anorexia
• Insomnia
• Fatigue
• (In children) reduced intelligence
• (In children) learning disabilities
• (In children) behavioural disorders

 

Signs

• Blueish lead line on gums 
• Pallor

Complications

• Renal hypertension
• Convulsions
• Korsakoff's syndrome 
• Encephalopathy
• Nephropathy
• Osteonecrosis
• Shock
• Coma

 

Investigations

• Full blood count : anaemia 
• Urea and electrolytes : impaired renal function
• Abdominal radiographs : passage of ingested metallic lead 

 

Management

• Chelation therapy
• Dimercaptosuccinic acid (DMSA)

Acetylcholinesterase inhibitors

Key Examples

• Donepezil
• Rivastigmine

 

Common indications     

1. Mild to moderate Alzheimer’s disease
2. Mild to moderate dementia in Parkinson’s disease (Rivastigmine)

 

Mechanisms of action     

• Acetylcholine is an important central nervous system (CNS) neurotransmitter, which is essential to many brain functions including learning and memory. 
• Once an action potential reaches the terminal axon of a motor neuron, acetylcholine is released from the presynapse and binds to the post-synpatic membrane to transmit signals across the synapse.
• The breakdown of acetylcholine is therefore essential to end acetylcholine signalling.
• A decrease in activity of the brain’s cholinergic system is seen in Alzheimer’s disease and in the dementia associated with Parkinson’s disease. 
• Acetylcholinesterase is an enzyme which degrades acetylcholine (ACh). 
• It is thought that by increasing the availability of acetylcholine for neurotransmission, they improve cognitive function and reduce the rate of cognitive decline. However, recovery of function in patients with these conditions on starting treatment is modest and not universal.

 

Important adverse effects     

• Nausea, diarrhoea and vomiting are the most common adverse effects, arising from increased cholinergic activity in the peripheral nervous system. These adverse effects may resolve over time. 
• Patients with asthma or chronic obstructive pulmonary disease (COPD) may experience an exacerbation of symptoms. 
• Less common, but serious, peripheral effects include peptic ulcers and bleeding, bradycardia and heart block. 
• Central cholinergic effects may induce hallucinations and altered/aggressive behaviour. These resolve with reduction of dose or discontinuation of therapy. 
• There is a small risk of extrapyramidal symptoms and neuroleptic malignant syndrome. These are discussed more fully in first-generation antipsychotics.

 

Warnings     

• Acetylcholinesterase inhibitors should be used with caution in patients with asthma and COPD and those at risk of developing peptic ulcers. 
• They should be avoided in patients with heart block or sick sinus syndrome. 
• Rivastigmine may worsen tremor in those with Parkinson’s disease.

 

Important interactions     

• Concomitant therapy with non-steroidal antiinflammatory drugs (NSAIDs) and corticosteroids may increase the risk of peptic ulceration. 
• Use alongside antipsychotics may increase the risk of neuroleptic malignant syndrome. 
• Bradycardia and/or heart block may occur when prescribed alongside other rate-limiting medications (e.g. β-blockers).

 

Other uses

• For the treatment of myasthenia gravis (MG)
• For the reversal of neuromuscular blockade (NMB)
• For pest control (lethal effects on pests)
• As a chemical weapon (lethal effects on humans)

Examples

• Carbamates (reversible) 
• Edrophonium : diagnosis of MG
• Pyridostigmine : treatment of MG, reversal of NMB
• Neostigmine : treatment of MG
• Physostigmine (eye drops) : glaucoma treatment 
• Rivastigmine: palliative treatment of dementia in Alzheimer disease or Parkinson disease
• Donepezil (reversible): palliative treatment of dementia in Alzheimer disease
• Organophosphates (irreversible)
• Echothiophate (eye drops) : glaucoma treatment

 

See also

• Organophosphate poisoning

[Toxicology] MDMA poisoning

Back to toxicology

MDMA (3,4-Methyl​enedioxy​methamphetamine) is also known as ectasy or molly.

In overdose, this can cause fatal arrhythmias, AKI, hyperpyrexia, and neurological disturbances. 

Iron poisoning

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Pathophysiology

In excessive quantities, iron is severely corrosive to the gastrointestinal tract. There is often nausea, vomiting and haematemesis.
Mucosal necrosis, ulceration, and ischaemia can be seen. Perforation of the GI tract may develop, rapidly resulting in hypovolaemic shock.

As iron is absorbed into the body it can cause:

• Metabolic acidosis. 
• Distributive shock through vasodilation. This is somewhat similar to the mechanism of shock during anaphylaxis. 
• Acute kidney injury.
• Fulminant liver failure.
• Disseminated intravascular coagulation.

All of these are life-threatening sequelae.

 

Management

• Immediate management of the acute situation on presentation.
• Chelation therapy with deferoxamine. 
• Dialysis.

Salicylate poisoning

Back to toxicology

[Toxicology] Poison database

Introduction to toxicology

• Pharmaceutical poisoning

• Organic compound poisoning

• Inorganic compound poisoning

• Biological poisoning

[Toxicology] Pharmaceutical poisoning

 Poison database

• Medication overdose 
• Acetylcholinesterase inhibitor overdose 
• Barbiturate overdose 
• Benzodiazepine overdose 
• Digoxin poisoning
• Dipyridamole overdose 
• Opioid overdose 
• Paracetamol overdose 
• Salicylate poisoning
• Tricyclic antidepressant overdose

• Hypervitaminosis 
• Vitamin A
• Vitamin D
• Vitamin E

• Recreational drug overdose
• MDMA poisoning 

[Toxicology] Organic compound poisoning

 Poison database

• Alcohol poisoning
• Ethanol poisoning
• Methanol poisoning 
• Ethylene glycol poisoning

• Carbon monoxide poisoning
• Cyanide poisoning
• Nicotine poisoning
• Nitrogen dioxide poisoning
• Organophosphate poisoning
• Oxygen poisoning 
• Pesticide poisoning 
• Toluene poisoning

[Toxicology] Inorganic compound poisoning

 Poison database

• Arsenic poisoning
• Cadmium poisoning
• Chlorine poisoning
• Copper toxicity  
• Fluoride toxicity
• Iron poisoning 
• Lead poisoning
• Mercury poisoning
• Selenium poisoning 
• Sulfuric acid poisoning

[Toxicology] Biological poisoning

 Poison database

• Bacterial toxins
• Anthrax toxin 
• Botulinum toxin

• Vertebrate toxins
• Fish toxins
• Ciguatera fish poisoning 
• Haff disease
• Ichthyoallyeinotoxism
• Scombroid food poisoning
• Tetrodotoxin

• Amphibian toxins
• Coturnism
• Reptile / snake venom 
• Kraits: bungarotoxin poisoning
• South American rattlesnake: convulxin poisoning 
• Mambas: dendrotoxin poisoning

• Invertebrate toxins
• Arthropods
• Bee venom
• Scorpion venom 
• Spider venom
• Tick paralysis
• Mollusca 
• Brevetoxin poisoning
• Conotoxin poisoning
• Domoic acid poisoning
• Eledoisin poisoning
• Onchidal poisoning
• Okadaic acid poisoning
• Saxitoxin poisoning 

• Mycotoxins (fungi)
• Aflatoxin poisoning
• Ergotism 
• Mushroom poisoning

• Plant toxins
• Cinchonism (quinism)
• Lathyrism
• Locoweed poisoning
• Ricin poisoning
• Strychnine poisoning  

Ecstasy poisoning

Back to toxicology

 

Tricyclic antidepressant overdose

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Aflatoxin

Aflatoxins are a group of carcinogenic toxins. 
Poisoning is known as 'aflatoxicosis'.

 

Produced by

• Aspergillus flavus
• Aspergillus parasiticus

 

Diseases

• Massive hepatic necrosis
• Cirrhosis 
• Hepatocellular carcinoma

Botulinum toxin

Also known as BOTOX.

• This is a toxin produced by Clostridium botulinum under specific environmental conditions.
• There are 8 types, named A to H. 
• Type H botox is the most lethal substance known. The human median lethal dose (LD50) is 1.3–2.1 ng/kg administered by IV or IM.

 

Pathophysiology

Acetylcholine is stored in vesicles inside the pre-synaptic terminal. These vesicles must fuse with the neuronal membrane to release acetylcholine into the synpase. Botox disrupts this fusion process, preventing acetylcholine release. This prevents neuromuscular signalling.

The effects of botox on the target proteins are permanent, so the effects on the nerves are very long-lasting. The effects only fade once the nerves have replaced the dysfunctional proteins. This can take weeks to months.

Botox is the mediator of botulism. This disease most commonly occurs when food contaminated with C. botulinum is prepared in specific conditions. The bacteria produce the toxin, which accumulates in the food.

Some forms of botulism are caused by active infection of the body with C. botulinum, which produces new toxin while living inside the body. These patients could benefit from anti-bacterial therapy. However, this is very rare. It usually occurs in infants, patients with immunocompromise or patients with abnormal bowel anatomy.

Medical uses

• Cosmetic therapy : Botox is famously used to paralyse muscles of facial expression, so that skin wrinkles appear less prominent. The effects are not permanent.
• Medical therapy : Botox injections can reverse muscle spasm or hypertonia in disorders such as achalasia. The effects are not permanent.

Ethanol poisoning

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Benzodiazepine overdose

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Benzodiazepines depress the CNS.
In overdose, the GCS and respiratory rate fall.

 

Management

• Medical therapy
• The reversal agent is flumazenil, a GABA_A antagonist (blocker) which counteracts benzodiazepines by competitive inhibition.
• Airway management
• Tracheal intubation
• Mechanical ventilation