geriatric pharmacology

Geriatric pharmacology is the study of how drugs behave in older adults and how to dose them safely. As the body ages it processes and reacts to medicines differently, and older people often take many drugs at once for several chronic conditions, so they are at once the heaviest users of medication and among the most vulnerable to its harms.

Ageing changes pharmacokinetics in fairly predictable directions. Kidney function declines gradually with age, slowing the removal of drugs cleared by the kidneys; liver mass and blood flow fall, slowing some metabolism; body fat rises while body water and muscle drop, which prolongs the action of fat-soluble drugs and concentrates water-soluble ones. The usual net effect is that drugs linger longer and can build up, so lower doses are often appropriate.

Pharmacodynamics shifts too, with older people frequently more sensitive to certain drug effects, especially on the brain and blood pressure, making them prone to confusion, sedation, falls, and fainting. The bigger danger, though, is often polypharmacy: the more drugs a person takes, the greater the chance of harmful drug interactions, of one drug being used to treat another's side effect, and of simple mix-ups.

A core principle is to start low and go slow, choosing the smallest effective dose and titrating cautiously, while regularly reviewing whether each medicine is still needed. Yet ageing is highly variable; a fit eighty-year-old may handle drugs better than a frail sixty-year-old, so chronological age alone is a rough guide and individual assessment matters more.