Makindo Medical Notes

Older adults are more vulnerable to adverse drug reactions (ADRs) due to age-related physiological changes, multimorbidity, and polypharmacy. Drug-related problems are a leading cause of hospital admissions in the elderly.

⚙️ Age-related Pharmacokinetic Changes

• 🩸 Absorption: Usually unchanged, but slower gastric emptying may delay onset.
• 💉 Distribution:
  • ↓ Total body water ➝ higher plasma concentration of hydrophilic drugs (e.g. digoxin, lithium).
  • ↑ Body fat ➝ prolonged half-life of lipophilic drugs (e.g. benzodiazepines, opioids).
  • ↓ Serum albumin ➝ more free (active) drug if protein-bound (e.g. warfarin, phenytoin).
• ⚙️ Metabolism:
  • ↓ Phase I metabolism (oxidation, reduction, hydrolysis) ➝ slower clearance of drugs like diazepam, theophylline.
  • Phase II metabolism (conjugation) usually preserved ➝ lorazepam, oxazepam safer choices.
• 🗑️ Excretion:
  • ↓ Renal clearance with age, even if creatinine appears “normal” (low muscle mass masks CKD).
  • High risk of toxicity from renally-excreted drugs: aminoglycosides, lithium, digoxin, DOACs.

⚠️ Common Adverse Drug Reactions in the Elderly

• 💔 Falls & fractures: Sedatives, antihypertensives, opioids, anticholinergics.
• 🧠 Delirium: Anticholinergics, benzodiazepines, opioids, steroids.
• 🫁 Constipation & retention: Opioids, anticholinergics, TCAs, antihistamines.
• 🩸 Bleeding: Warfarin, DOACs, antiplatelets, NSAIDs.
• 🫀 Electrolyte imbalance: Diuretics (hypoNa/K/Mg), ACEi/ARBs (hyperK), PPIs (hypoMg).
• 🦴 Osteoporosis/fractures: Long-term steroids, PPIs, anticonvulsants.

📋 Principles of Prescribing in the Elderly

• 📉 Start low, go slow: Begin at half-dose, titrate cautiously.
• 🔍 Regular reviews: Check ongoing indication, adherence, side effects.
• ⚖️ Deprescribing: Stop drugs with more risk than benefit, esp. in frailty/end of life.
• 📚 Evidence-based tools: STOPP/START criteria, Beers criteria.
• 💊 Simplify regimens: Minimise dosing frequency; use blister packs/Dosette boxes.
• 🧑‍🤝‍🧑 Involve pharmacists: Medication reconciliation, polypharmacy clinics.

🔎 High-Risk Drug Classes

• 💊 Anticholinergics: Cause delirium, constipation, urinary retention.
• 🩸 Anticoagulants/antiplatelets: Bleeding risk; always balance stroke vs bleed risk.
• 😴 Benzodiazepines/Z-drugs: Falls, delirium, dependence — avoid long-term.
• 💔 NSAIDs: GI bleed, renal injury, fluid retention — avoid chronic use.
• 🧪 Diuretics: Electrolyte imbalance, postural hypotension ➝ falls.

🧠 Special Topics

• 🧩 Polypharmacy: ≥5 regular drugs (common in 50% of >65s) ➝ higher ADR risk.
• 🧠 Dementia: Avoid anticholinergics & sedatives; consider cholinesterase inhibitors.
• 🛌 Palliative care: Deprescribe preventatives (statins, bisphosphonates) if prognosis short.
• 🧮 Renal dosing: Always use eGFR, not serum creatinine alone, to guide dosing.

📝 OSCE / Exam Pearls

• Always say: “Elderly have reduced renal clearance even with normal creatinine.”
• Mention STOPP/START criteria when asked about polypharmacy.
• In prescribing stations: “Start low, go slow, but don’t stop too soon if benefit clear.”
• Link ADRs to presentations: falls, delirium, AKI, confusion, constipation.

🧑‍⚕️ Case Examples — Pharmacology in the Elderly

• Case 1 (Polypharmacy & falls): 🤕 An 84-year-old woman with hypertension, diabetes, and osteoarthritis is on 8 regular medications, including amlodipine, gliclazide, and codeine. She presents with recurrent falls and dizziness. Review reveals postural hypotension and opioid-related sedation. Deprescribing codeine and rationalising antihypertensives reduces her fall risk. Teaching point: polypharmacy is a major risk factor for adverse drug events in the elderly; regular medication reviews are essential.
• Case 2 (Renal impairment & drug accumulation): 🩸 A 90-year-old man with CKD stage 4 is prescribed digoxin for atrial fibrillation. He presents with nausea, confusion, and visual halos. Serum digoxin is elevated. Dose adjustment and monitoring of renal function are critical, as clearance is reduced with age. Teaching point: always adjust renally-excreted drugs in older adults with CKD.
• Case 3 (Anticholinergic burden): 🧠 A 76-year-old woman with COPD and urinary incontinence is prescribed tiotropium and oxybutynin. She develops worsening confusion, constipation, and urinary retention. The combined anticholinergic load is the culprit. Oxybutynin is stopped and switched to a safer alternative. Teaching point: high anticholinergic burden increases risk of delirium, constipation, and urinary retention in the elderly.
• Case 4 (Warfarin vs DOAC): 💊 An 82-year-old man with atrial fibrillation is on warfarin but has fluctuating INRs and frequent clinic visits. After discussion, he is switched to apixaban. This reduces monitoring burden and has a safer bleeding profile in the elderly. Teaching point: DOACs are often preferable to warfarin in frail older adults, but renal function and drug interactions must be checked.
• Case 5 (NSAID-related GI bleed): 🩸 A 79-year-old woman with osteoarthritis takes ibuprofen daily without gastroprotection. She presents with melaena and iron-deficiency anaemia. Endoscopy confirms a gastric ulcer. NSAID discontinued, PPI started, and paracetamol used for pain control. Teaching point: NSAIDs increase risk of GI bleeding and renal impairment in older adults; co-prescribe PPIs if essential.
• Case 6 (Benzodiazepine dependence): 😴 An 85-year-old man has been on nightly diazepam for insomnia for several years. He now has memory impairment, day-time drowsiness, and recurrent falls. Gradual tapering and referral to sleep hygiene programme initiated. Teaching point: avoid long-term benzodiazepines in the elderly due to cognitive decline, dependence, and fall risk.
• Case 7 (Hypoglycaemia from sulfonylureas): 🍬 A 77-year-old woman with type 2 diabetes on gliclazide collapses at home with sweating and confusion. Capillary glucose is 2.2 mmol/L. Treated with IV glucose; gliclazide stopped and switched to DPP-4 inhibitor. Teaching point: older adults are at high risk of severe hypoglycaemia with sulfonylureas — safer alternatives are available.
• Case 8 (Beers criteria — inappropriate drug): 📋 An 80-year-old man with BPH is prescribed amitriptyline for neuropathic pain. He develops urinary retention and worsening constipation. Switched to duloxetine after medication review. Teaching point: the Beers criteria highlight drugs that should generally be avoided in older adults — tricyclic antidepressants are a key example.