Pharmacology and Polypharmacy
What to know
Polypharmacy (≥5 medications) and potentially inappropriate medications (PIMs) are central. Use Beers Criteria and STOPP/START to identify PIMs: anticholinergics, benzodiazepines, long-acting sulfonylureas, NSAIDs, and sedative-hypnotics. Pharmacokinetic changes: reduced renal clearance, decreased hepatic metabolism, lower body water (higher concentration of water-soluble drugs), increased fat (prolonged half-life of lipophilic drugs). Pharmacodynamic changes increase sensitivity to sedatives and anticoagulants. Deprescribing is a structured process: identify, prioritize, taper, monitor. Anticholinergic burden contributes to confusion, constipation, and urinary retention.
Traps
Questions test recognizing drug-induced syndromes: falls (sedatives, antihypertensives), delirium (anticholinergics, opioids), and hypoglycemia (sulfonylureas). Don't add a drug to treat a side effect of another (prescribing cascade). Remember renal dosing. Avoid abrupt discontinuation of some drugs (e.g., benzodiazepines, beta-blockers, corticosteroids) without tapering.
Rule of thumb
"Start low, go slow, and stop when possible": titrate carefully and reassess the need for every medication.
Worked example
An elder with confusion, dry mouth, constipation, and urinary retention on multiple drugs: calculate anticholinergic burden; deprescribe the highest-burden agent(s) and monitor.
Worked example 2
A patient with falls on a benzodiazepine: taper gradually rather than stopping abruptly.