Poisoning & STOPP/START Flashcards
What is pharmacological toxicity?
Pharmacological toxicity is either:
A predictable extension to desired effect (e.g insulin causing hypoglycaemia or warfarin causing haemorrhage)
A secondary effect not related to the primary aim of treatment (e.g teratogenicity of thalidomide or B-agonists causing tachycardia in asthmatics)
An effect normally only seen in large overdose (e.g. opioids causing respiratory depression or B-blockers causing myocardial depression)
What is biochemical toxicity?
When a drug or active metabolite causes cellular damage - macromolecules inc. structural proteins and enzymes.
Most drugs that reach market have been tested extensively for toxicity but, at supratherapeutic levels build up of toxic metabolites is possible.
The balance of elimination of a drug or metabolites will dictate the potential harm that may be caused.
How do you overcome biological toxicity?
Understanding the mechanism of toxicity has, in some cases, allowed us to develop suitable pharmacological treatments.
For example:
Thiol group found on endogenous glutathione can prevent cell damage caused by highly reactive chemical metabolites - e.g. acetylcysteine in paracetamol overdose.
MESNA when prescribing cyclophosphamide to reduce the risk of bleeding from the bladder (haemorrhage cystitis).
What are the management principles of overdose?
Immediate actions Supportive actions Enhance elimination Antidotes Prevention of absorption
What do you do immediately if a person presents with overdose?
Remove person from contact with poison - typically you will be presented with somebody significantly after the event(s)
Vital signs and injury
History - from the patient if you can, chaperone, evidence - packaging
What could causes these complication?
Cardiac arrest Arrhythmia Hypotension Renal failure Respiratory depression Hepatic failure Seizures
Cardiac arrest - Hypoxia, electrolyte and metabolic disturbance, cardiac toxicity
Arrhythmia - hypoxia, electrolyte and metabolic disturbance, cardiac toxicity
Hypotension - myocardial depression, peripheral vasodilation
Renal failure - hypotension, rhabdomyolysis, direct nephrotoxicity
Respiratory depression - Direct neurotoxicity
Hepatic failure - direct hepatotoxicity
Seizures - Hypoxia, direct neurotoxicity
How do you prevent absorption?
Gastric levage almost never recommended due to risk of aspiration
Activated charcoal - large absorbent area given as suspension in water.
Large quantities needed - 10:1
Timing of overdose makes the efficacy of the charcoal unpredictable
Not suitable for drowsy or comatose patients - aspiration
How do you help elimination?
Continue activated charcoal - up to 36hrs, benzodiazepines, phenobarbital
Sodium bicarbonate - alkaline diuresis - increase pH <7.5 - salicylate poisoning
Force diuresis not recommended because of risk of serious electrolyte imbalance
Haemodialysis - small Vd - seriously ill patients.
What antidotes can be given for poisoning?
Competitive antagonists - Naloxone, Atropine
Chelating agents - complex with poison, reduce free drug - sodium nitrate or sodium thiosulphate for cyanide poisoning
Manipulating drug metabolism - Fomepizole, Acetylcysteine
Antibodies / antivenom - Digoxin specific antibody - binds to digoxin, preventing action and renal excretion
What are clinical reviews and why are they needed?
Either involves chancing repeats and what is on script to a full clinical medication review - discuss medicines and condition with the patient.
Important as it ensures the patient receives the right medication at the right time so it improves clinical outcomes and the economy.
Especially important if a patient is polypharmacy.
What patients should be particularly targeted for review?
People taking lots of meds Complex medication regimens Recently discharged Frequent admissions to hospital Cormorbidities Medications prescribed from multiple sources High risk meds - narrow therapeutic window, known and serious side effect profile Longterm use of psychotropic drugs
What things should be checked during a medicines review?
Is medication right for the patient?
Time limited medications
Age-life expectancy and risk benefit
Is the medication effective?
Cost - suitable generics
Appropriate tests to support decisions.
Drug interactions
Contraindications
Side effects
Concordance
Over the counter ad complimentary medicines
Lifestyle modifications
What is STOPP./ start?
Screening Tool of Older Peoples Prescriptions and Screening Tool to Alert to Right Treatment.
Screening tool introduced and validated in 2008.
Used for patients 65+ in conjunction with clinical judgement.
How do you implement the changes?
Record discussion and changes in patients notes - often templates are available to prompt appropriate detail and free text comments.
Communication if change is vital -
Review of changes - impact - functions and holistic longer term review schedule agreed.
