Toxicology

Question 1

what resources can be used for toxicology information?

Answer 1

TOXBASE and national poisons information services (NPIS)

Question 2

what are the types of poisoning?

Answer 2

1. acute - rapid intake of poisoning agent
2. chronic - mainly due to prolonged exposure
   e.g. industrial/ manufactoring/ occupational related
3. accidental
   e.g. children accidentally ingesting
4. intentional overdosing

Question 3

what is the main cause of overdosing?

Answer 3

paracetamol overdosing
ibuprofen overdosing
sertraline overdosing
even caffeine

Question 4

what are the clinical features of poisoned patients also known as?

Answer 4

toxidomes

Question 5

what are the clinical features of poisoned patients?

Answer 5

1. opioid
2. serotonergic
3. anticholinergic
4. cholinergic
5. sympathomimetic

Question 6

what are the clinical features of opioid poisoning?

Answer 6

pinpoint pupils
reduced GCS (Glasgow coma scale)
reduced respiratory rate

Question 7

what are the clinical features of serotonergic poisoning?

Answer 7

agitation
delirium
tremor
tachycardia
labile BP
sweating
hypertonia
brisk reflexes
clonus
fever
serotonin symptoms

Question 8

what are the clinical features of anticholinergic poisoning?

Answer 8

Dilated pupils
Warm, dry skin
Confusion, restlessness, hallucinations – Brisk reflexes, myoclonic jerks
Tachycardia
Urine retention

Question 9

what are the clinical features of cholinergic poisoning?

Answer 9

pin point pupils
Bradycardia
Sweating
Excessive secretions
-Hypersalivation
-Lacrimation
-Rhinorrhoea
-Bronchorrhoea
-Diarrhoea

Question 10

what are the clinical features of sympathomimetic poisoning?

Answer 10

Hypertension, tachycardia
dilated pupils
Sweating
Agitation, paranoia, psychosis
Hyperreflexia
Stereotypy
Hyperpyrexia

Question 11

what is Glasgow coma scale (GCS)?

Answer 11

consciousness scale
15 max score = conscious pt
3 = deep coma/brain dead

Question 12

what drug examples of serotonergic poisoning?

Answer 12

Ecstasy
antipressants
SSRI’s
e.g. sertraline

Question 13

what drug examples of anticholinergic poisoning?

Answer 13

poisons berries

Question 14

what drug examples of cholinergic poisoning?

Answer 14

organophosphates - industrial exposure

Question 15

what drug examples of sympathomimetic poisoning?

Answer 15

amphetamines
ecstasy (impure)

Question 16

how to assess poisoning clinically?

Answer 16

Routine blood tests
* ABG
–COHb
–MetHb
* Anion gap + osmolal gap
* Analytical toxicology
–Emergency measurement
* Salicylate, iron, theophylline, methanol, ethylene glycol,
lithium, phenytoin, carbamazepine

–Screening for overdose of…
* Paracetamol
* Drugs of abuse

Question 17

what causes an increased anion gap?

Answer 17

– Ketoacidosis
– Lactic acidosis
– Salicylate overdose
– Alcohols: ethanol, methanol, ethylene glycol
– Renal failure
– Rhabdomyolysis

Question 18

what is an anion gap

Answer 18

Question 19

what is an osmolal gap

Answer 19

Question 20

what is the general management for poisoning?

Answer 20

Supportive care of symptoms
Prevention of absorption
Enhancement of elimination
Specific antidotes - less common

Question 20

what causes an increased osmolal gap?

Answer 20

– Ethanol
– Methanol
– Ethylene glycol
– Acetone
– Isopropanol

Question 21

how to prevent absorption

Answer 21

1. emetics - not recommended
2. gastic lavage - rarely used
3. activated charcoal to mop the drug up
4. whole bowel irrigation if they carry body packers

Question 22

how to enhance elimination

Answer 22

Multiple dose activated charcoal x3/4 a day
– Carbamazepine, colchicine, quinine, theophylline, phenobarbital * Urine alkalinisation
– Aspirin
* Extracorporeal
– Haemofiltration
– Haemodialysis

Question 23

what antidotes must be given within an hour

Answer 23

Question 24

what are the type of mechanism for antidotes?

Answer 24

1. form an inert complex with poison 2. accelerate detoxification of poison 3. reduce rate of conversion to a more toxic compound 4. compete with toxic substances for essential receptor sites 5. block essential receptor through which they exert their toxic effects to 6. bypass the effect of the poison

Question 25

when is intralipids given?

Answer 25

reversal of local anaesthetics overdose during surgery

Question 26

how does intralipids reverse anaesthetic overdose?

Answer 26

acts as a lipid sink drugs distribute to the lipid phase

Question 27

what is ethylene glycol?

Answer 27

antifreeze metabolised in the liver by alcohol dehydrogenase = toxic metabolites formed cause death to kidneys and liver due to metabolic acidosis and inhibition of OXPHOS and protein synthesis

Question 28

what is the treatment of ethylene glycol poisoning?

Answer 28

* Ethanol –ADH has greater affinity for ethanol –Decreases formation of toxic metabolites – Serum concentration >100mg/dl should be achieved * Fomepizole (4-methylpyrazole) –Potent inhibitor of ADH –Easier to administer, predictable pharmacokinetics –Expensive and not readily available * Haemodialysis –Definitive treatment to remove parent compound and its metabolites

Question 29

why is ethanol toxic?

Answer 29

Causes retinal and optic nerve toxicity and blindness

Question 30

what drug can prevent ethanol/ADH causing retinal toxicity/blindness?

Answer 30

fomepizole

Question 31

what are sources of cyanide poisoning?

Answer 31

Cyanide in fire smoke – Natural substances * Wool * Silk * Cotton – Synthetic * Plastics * Nylon * Polyurethranefoam

Question 32

what are cyanide antidotes?

Answer 32

Oxygen Methaemoglobin inducers (sodium nitrite) Dicobalt edetate Hydroxocobalamin (Cyanokit)

Question 33

what are sources of lead poisoning?

Answer 33

Occupational * Inhalation of lead dust or fumes in lead-using industries (lead- acid battery manufacturing and recycling; mining, smelting and refining of lead and other ores) * During demolition/renovation of old properties. Non-occupational * House renovation, lead paint, imported toys or cookware, pica, old lead pipes, contaminated traditional remedies or cosmetics.

Question 34

what are symptoms of lead poisoning?

Answer 34

abdominal pains, headache, raised BP, lethargy, poor concentration, memory difficulties, constipation (may be severe), anaemia. * Peripheral neuropathy uncommon. * Encephalopathy only occurs with very severe poisoning and is more common in children than adults. * Renal effects include reversible proximal tubular dysfunction and, in more severe cases, irreversible interstitial fibrosis and progressive renal insufficiency.

Question 35

what are lead antidotes?

Answer 35

Oral DMSA (succimer) IV sodium calcium edetate