25 - Poisoning and STOPP START Flashcards
What is pharmacological toxicity usually due to?
A predictable extension of the desired effect of the drug at the known site
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Give some examples of how the following drugs can have pharmacological toxicity at slightly supratherapeutic doses:
- Warfarin
- Loop Diuretic
- AChE Inhibitors
Insulin
Exaggeration of their desired effect
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What are some of the pharmacologically toxic effects of the following (not related to the drugs usual desired effects):
- Statin
- B-agonist
- Thalidomide
- B-blocker
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What are some effects seen in large overdoses of the following drugs:
- Beta Blocker
- Opioids
- Theophylline
- Carbamazepine
- Phenobarbital
- Myocardial depression
- Respiratory depression, tachycardia, hypotensive
- Convulsions, arrhythmias
- Respiratory depression
- Respiratory depression
Identify five common UK poisons.
- Paracetamol
- Hypnotics (diazepam, zoplicone)
- Salicylates
- Ecstasy
- Opiates
What is biochemical toxicity?
- A drug or active metabolite which causes cellular damage to macromolecules such as structural proteins and enzymes
- Drugs on the market are tested for this but at supratherapeutic doses they often have build up of toxic metabolites
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What are the antidotes for an overdose of the following drugs:
- Digoxin
- Cocaine
- Paracetamol
- Benzodiazepene
- Opiate
- Beta Blocker
- Can also give chelating agents that complex with the poison to reduce the amount of free drug (e.g in lead, cyanide and iron salt poisoning)
- Digibound is antibody (so is antivenom)
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How does the antidote for paracetamol overdose work?
N-Acetyl Cysteine
- Donates thiol to glutathione to drive phase 2 and prevent build up of toxic metabolites to stop centrilobular necrosis
- In OD the glutathione is saturated so cannot conjugate anymore NAPQI so build up of NAPQI
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How can we overcome biological toxicity of drugs that are used at therapeutic levels e.g the DMARD cyclophosphamide?
- Use Mesna 2 hours before orally or in IV with cyclophosphamide
- Has a thiol group for cytoprotection and a polar group so it can get renally excreted and get to the right place to protect bladder epithelium
- Mesna helps stop haemorraghic cystitis
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In general what are the management principles for a drug overdose?
Immediately:
- Remove person from contact with poison
- Take vital signs and look for injuries
- Take history from patient, chaperone, written notes or packaging
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What are some scenarios you need to consider that might need supportive measures to correct when a person is having a drug overdose?
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How can we prevent absorption of a drug and increase it’s elimination in a drug overdose?
- Never gastric lavage due to risk of aspiration
- Give lots of activated charcoal in water if conscious to prevent absorption
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What is fomepizole used for?
Stops ethylene glycol and methanol poisoning by altering the metabolism to stop the production of toxic metabolites
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What is the antidote for organophosphate poisoning?
ATROPINE: Antimuscarinic
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What is polypharmacy?
When a patient is taking 4-6+ medicines concurrently