College Answer

2-year-old child                                                                                                     

• Ingested agent likely to be non-pharmaceutical
• Vast majority of ingestions are benign
• Other children may be affected (siblings, playmates)
• Doses ingested likely to be small (2-3 tablets or small handful) and toxic effects mg/kg the same as adults but some agents can be potentially lethal for a toddler if even 1-2 tablets taken (e.g. amphetamines, Ca channel blockers, sulphonylureas) or a mouthful (e.g. organophosphate insecticides, eucalyptus oil, one mothball)
• Unlikely to obtain accurate dosing history – risk assessment and management based on “worst-case scenario”
• Need admission to health care facility with resources for paediatric resuscitation
• Regular check of blood sugar levels
• Usual toxicology screening tests for adult patient not necessary
• GI decontamination with activated charcoal is not routine because of increased risks with aspiration – reserved for severe or life-threatening poisoning where supportive care or antidote treatment alone is inadequate
• If severe intoxication suggesting large, repeated or unusual exposure, consider NAI

30/40 pregnant female                                                                                       

• Risks to mother and foetus
• Pregnancy-induced physiological changes impact on drug pharmacokinetics
• Delayed gastric absorption and GI transit time slows drug absorption and increases period of potential benefit for decontamination
• Increased blood volume increases V_D and decreases drug plasma levels
• Dilution of plasma proteins increases free drug levels 
• Hepatic enzyme systems altered by circulating hormones
• Increased cardiac output increase renal blood flow and GFR
• Hypovolaemia and respiratory compromise may go unrecognised until at a late stage
• A few agents pose increased risk to foetus and treatment threshold is lowered (e.g.
• salicylates, CO, lead, MetHb-inducing agents)
• Excellence in supportive care for the mother ensures best outcome for foetus
• Obstetric and neonatal as well as toxicology input needed including decision for emergency delivery of baby.

75-year-old with CKD                                                                                           

• Limited physiological reserve, deteriorating cognition, multiple co-morbidities and polypharmacy lead to exaggerated and unpredictable response in poisoning
• More severe clinical course for same dose of same agent taken by healthy young adult
• Pharmacokinetic changes with ageing and CKD o Delayed GI absorption o Decreased protein binding and increased free drug levels o Reduced liver function with decreased drug metabolism o Reduced renal function and reduced elimination o Baseline CKD likely to be made worse o “Therapeutic” drug doses may be toxic
• Pharmacodynamic differences from drug effects on impaired organs e.g. poor ability to respond to CVS, respiratory and CNS depressant agents
• Greater incidence of complications e.g. delirium, pneumonia, thrombo-embolism
• Longer ICU and hospital stay

Discussion

This is another one of the questions in this paper which had a 0% pass rate. Locally available resources include the following chapters:

• Pharmacology and toxicology of childhood
• Pharmacology and toxicology of pregnancy
• Pharmacology and toxicology of old age

The answer would probably work better as a table: