Lecture 27 - Poisoning Flashcards
What is the difference between adverse drug reactions and drug toxicity?
ADR = typical reactions seen at the therapeutic doses of the. Drug
Drug toxicity = associated with effects that occur at supra therapeutic
What is the most common pharmacological toxicity?
Predictable extension of its desired effect (e.g diuretic leading to hypovolaemia)
What is a beneficial side effect of loperamide?
Mechanism of action
A type of opioid which works on (agonist) the Mu opioid receptors in the Myenteric plexus leading to decreased gut motility
Helps treat diarrhoea
What is a benefical side effect of chlorpromazine?
Used as anti-emetic in palliative (is an antipsychotic sedative)
What are some predictable side effects of:
-warfarin
-insulin
-loop diuretic
-ACh esterase inhibitor
Warfarin = bleeding
Insulin = hypoglycaemia
Loop diuretic = hypokalaemia
-SLUDGE
What is a secondary effect not related to the primary aim of the treatment of statins?
Rhabdomyolysis
What is a secondary effect not related to the primary aim of the treatment of thalidomide?
Teratogenic
What is a secondary effect not related to the primary aim of the treatment of B agonists?
Bronchospasm in asthmatics
What is a secondary effect not related to the primary aim of the treatment of B blocker?
Bradycardia
What is often prescribed alongside a chemotherapeutic agent?
Anti emetics
What is often prescribed alongside methotrexate?
Folic acid
What is a drug class that can cause resp depression if overdosed?
Opioids
What is a drug class that can cause myocardial depression if overdosed?
B blockers
What drug toxicity is seen in overdose of carbamazepine and phenobarbital (works on GABA receptors)?
Respiratory depression
What drug toxicity is seen in overdose of theophylline (methyl xanthine)?
Convulsions
Arrhythmias
What is biochemical toxicity?
Destruction of cells or cellular damage from a drug or active metabolite
What is the mechanism of biological toxicity in paracetamol overdose?
Glutathione gets overwhelmed so toxic metabolites of paracetamol accumulate
How does Glutathione prevent toxicity from paracetamol?
Donates thiol group
How do you treat paracetamol overdose?
Give Acetylcysteine which replenishes the thios which glutathione can donate
What is a very toxic side efefct of cyclophosphamide?
Haemorrhagic cystitis
What is cyclophosphamide typically used to treat?
Severe rheumatoid arthritis.
What is given alongside cyclophosphamide to prevent the development of haemorrhagic cystitis?
Mesna and or aggressive hydration
How does Mesna prevent Haemorrhagic cystitis with cyclophosphamide?
Has thiol group for cytoprotection and polar group
Hash a high renal excretion and protection at bladder epithelium
What are the general management principles for treating an overdose?
Prevent absorption
Enhance elimination
Antidotes
Supportive measures
What are the immediate. Actions taken when someone has been poisoned?
Remove person from contact with poison
Assess vital signs and injury
Good history
What are some methods of preventing absorption of a toxin/poison?
Gastric lovage (stomach pumping)
Activated charcoal
Why is gastric lavage rarely used?
Risk of stomach aspiration
What patients is activated charcoal not suitable for?
Drowsy or comatose patients
What are some methods that we can enhance elimination of a poison?
Activated charcoal
Sodium bicarbonate (alkkkaline diuresis) for salicylate poisoning
Haemodialysis
What are some examples of competitive antagonist antidotes?
Naloxone
Atropine
What is the mechanism of action of Naloxone as an antidote?
Antagonist to Mu opioid receptors for opioid overdose
What is atropine used as an antidote for?
Organophosphate poisoning
What is the effect of organophosphate poisoning?
Organophosphate inhibit Acetylcholine esterase leading to very high levels of ACh causing SLUDGE syndrome
How does atropine act as an antidote to organophosphate poison gin?
Blocks Muscarinic ACh receptors decreasing effect of elevated ACh
How do chelating agents work as antidotes?
Form complex with poison reducing free drug
What toxins do chelating agents work as an antidote for?
Cyanide
Lead
Iron salts
What is a drug that manipulates drug metabolism involving alcohol?
Fomepizole
How does fomepizole manipulate drug metabolism?
Inhibts alcohol dehydrogenase
What is an example of antibodies/antivenoms?
Digoxin specific antibody
What patients should be particularly targeted for drug review?
Elderly
Those with comorbidities
Pregnant
Those just admitted and just about to be discharged
What are some pharmacokinetic and pharmoacodynamic changes in the elderly?
Inc fat, less Body water
Renal mass and function reduced
Reduced hepatic function and blood flow
Lower GI absorption
Inc GI bleed risk
Reduced barocetpor sensitivity
Reduced first pass metabolism
Receptor expression changes
What needs to be thought about in a drug review?
Is med right for patient
Age, life expectancy
Risk Vs Benefit
Is it effective
Suitable cost
Appropriate tests to support decision
What is the STOPP-START programme?
Screening tool used to review drugs patients are taking
What age range is the STOPP-START patients used for?
> 65s
What does STOPP-START mean?
Screening Tool of Older Peoples Prescriptions and Screening Tool to Alert to Right Treatement
Aims to highlight and prevent inappropriate prescribing
