Geriatric Pharmacology

Geriatric Pharmacology

1. Definition, scope & why the elderly are a special population

• Geriatric pharmacology is the study of how the physiological changes of ageing alter drug handling (pharmacokinetics) and drug response (pharmacodynamics), and of the consequent need to individualise drug choice, dose and regimen in older adults. (KDT 8e Ch.5, pp.73–5)
• Age is a recognised patient factor that modifies drug action alongside body size, sex, species/race, genetics, route, disease and drug interactions; effects are usually quantitative (plasma level/effect ↑ or ↓, correctable by dose adjustment) rather than qualitative. (KDT 8e Ch.5, pp.73–4)
  • "The elderly" in pharmacology is conventionally taken from ~65 years, but functional decline is continuous from middle age — KDT anchors renal-function landmarks at 50 and 75 years. (KDT 8e Ch.5, p.74)
• Older adults are pharmacologically vulnerable because declining renal and hepatic clearance, altered body composition and lowered albumin combine with multimorbidity, polypharmacy and altered tissue sensitivity to widen the gap between effective and toxic exposure. (KDT 8e Ch.5, pp.74–5)
• Volume of distribution itself is age-dependent: a drug's V "can differ according to a patient's age, gender, body composition, and presence of disease" — so the same dose yields different exposure in an older versus a young adult. (G&G 14e Ch.2, p.34)
• The elderly (with children, pregnant/lactating women and renal/hepatic-impaired patients) are routinely excluded from pre-marketing clinical trials; dosing evidence in this group is therefore often generated only at the Phase 4 / post-marketing stage. (KDT 8e Ch.5, pp.81–2)
  • Clinical consequence: much geriatric dosing rests on extrapolation and post-marketing surveillance rather than dedicated RCT data — a structural reason for cautious, individualised prescribing.