Why Prescribing for Older Adults Is Different

Prescribing medicines for older adults is not simply prescribing for adults in miniature. From the mid-sixties onward — though the boundary is not exact — the body handles medicines differently, and the sheer number of conditions an individual may live with means that a single prescription rarely exists in isolation. Understanding why prescribing changes with age is essential for clinicians, pharmacists, patients, and families who want to make informed decisions about medicine use in later life.

How ageing changes medicine handling

The way a medicine is absorbed, distributed, broken down, and eliminated — collectively its pharmacokinetics — shifts as the body ages. Total body water and lean muscle mass tend to decrease, while the proportion of body fat often increases. Water-soluble medicines may therefore reach higher concentrations in the blood because there is less volume for them to dissolve into, while fat-soluble medicines may accumulate over time because they are stored in fat tissue and released more slowly.

Kidney function generally declines with age, even in the absence of diagnosed kidney disease. Since many medicines and their breakdown products are removed from the body through the kidneys, reduced renal function means that certain drugs linger longer and can build up to potentially harmful levels. Liver changes are subtler: overall liver size and blood flow decrease, though the enzyme systems that process many medicines remain relatively intact. The net effect is that older adults are often more sensitive to medicines than younger people taking the same dose, and they may take longer to clear a drug from their system.

Polypharmacy and prescribing cascades

Polypharmacy is commonly defined as the regular use of five or more medicines at the same time. It is not inherently inappropriate — an older adult with several well-managed chronic conditions may genuinely need multiple medicines — but it does increase the complexity of treatment and the potential for medicine interactions, adverse effects, and difficulties with adherence.

A particularly important concept is the prescribing cascade. This occurs when a side effect of one medicine is mistaken for a new medical condition, leading to a second prescription that would not have been needed otherwise. For example, a medicine causing dizziness might be followed by a prescription for something to address the resulting falls, without recognising the original cause. Each additional medicine adds its own potential side effects and interactions, and the cycle can deepen. Recognising and interrupting these cascades is a key part of reviewing an older person's medicine regimen.

Tools for safer prescribing

Several structured tools have been developed to help clinicians identify medicines that may carry disproportionate risks in older adults. The Beers Criteria, published and periodically updated by the American Geriatrics Society, is one of the most widely referenced. It lists medicines and medicine classes that are potentially inappropriate for most older adults, either because safer alternatives exist, because age-related changes make them riskier, or because they compound common problems such as falls, confusion, or low blood pressure.

Another widely used framework is the STOPP/START criteria (Screening Tool of Older Persons' Prescriptions / Screening Tool to Alert to Right Treatment), which flags both medicines that should generally be stopped in older adults and treatments that are commonly omitted but should be considered. These tools are reference guides rather than rigid rules. Each patient's circumstances — including life expectancy, goals of care, and individual tolerability — must guide decisions. A medicine flagged by the Beers Criteria may still be the right choice for a particular person if the benefits clearly outweigh the risks and no suitable alternative exists.

Deprescribing as a concept

Deprescribing is the planned and supervised process of reducing the dose or stopping a medicine that may no longer be needed, may be causing harm, or may no longer align with a person's current health goals. It is not about denying treatment; it is about ensuring that every medicine on a person's list still earns its place. Deprescribing often involves gradual dose reduction, careful monitoring for withdrawal effects or returning symptoms, and ongoing conversation between patient and clinician.

The concept has gained momentum as evidence accumulates that more medicines do not always mean better outcomes, particularly in frail older adults or those nearing the end of life. Some medicines prescribed years ago for a condition that has since resolved, or started when life expectancy was different, may simply have never been revisited. In South Africa, where a growing older population intersects with a health system managing both infectious and non-communicable diseases, routine medicine reviews — including deprescribing where appropriate — are increasingly relevant. Patients and caregivers can support this process by asking whether each medicine is still necessary and whether any could be safely reduced, and by using tools such as the HealthSA search to confirm the registration status and Single Exit Price of medicines being reviewed.