Geriatric Toxicology

Geriatric toxicology addresses why older adults are more susceptible to drug toxicity and adverse exposures. Ageing reduces hepatic and renal clearance, changes body composition, and increases the sensitivity of some target tissues, while multiple chronic illnesses and the use of many medications together raise the chance of harmful drug accumulation and interaction.

Definition

Geriatric toxicology is the study of the increased vulnerability of older adults to toxic effects of drugs and other agents, driven by age-related declines in drug clearance, altered body composition and pharmacodynamic sensitivity, and the compounding effects of multimorbidity and polypharmacy.

Scope

The topic covers the age-related pharmacokinetic and pharmacodynamic changes that heighten susceptibility, the role of polypharmacy and potentially inappropriate medications, and the resulting pattern of adverse drug events in later life. It explains mechanisms and risk and is not a source of prescribing, deprescribing, or dosing guidance.

Core questions

• How do age-related declines in liver and kidney function change the clearance and accumulation of drugs?
• Why can older adults be more sensitive to a drug's effect even at the same plasma concentration?
• How does taking many medications at once raise the risk of toxicity and interaction?
• What makes some medications potentially inappropriate in older adults?

Key concepts

• Age-related decline in renal and hepatic clearance
• Altered body composition and volume of distribution
• Increased pharmacodynamic sensitivity
• Polypharmacy and drug-drug interaction
• Potentially inappropriate medications
• Anticholinergic burden
• Reduced homeostatic reserve

Mechanisms

With ageing, glomerular filtration and hepatic metabolic capacity decline, so many drugs are cleared more slowly and accumulate to higher concentrations for a given exposure. Body composition shifts toward a higher proportion of fat and lower body water, changing the distribution of lipophilic and water-soluble agents. Independently of these pharmacokinetic changes, target tissues can become more sensitive, so a given concentration produces a larger effect - older adults are, for example, more susceptible to the sedative, hypotensive, and anticholinergic effects of many drugs. Reduced homeostatic reserve means the body buffers perturbations less well. These factors are amplified by multimorbidity and polypharmacy, which multiply opportunities for drug-drug interaction and cumulative burden, particularly cumulative anticholinergic load.

Clinical relevance

Geriatric toxicology explains why adverse drug events are common in later life and underlies tools used to flag potentially inappropriate medications. The entry is educational, describing the mechanisms and epidemiology of heightened susceptibility in older adults; it is not a basis for individual prescribing, deprescribing, dosing, or treatment decisions.

Epidemiology

Older adults experience a disproportionate burden of adverse drug events and drug-related hospitalizations relative to younger adults, reflecting both physiological susceptibility and high rates of polypharmacy; cumulative anticholinergic exposure in particular has been associated with cognitive impairment, falls, and increased mortality in this group.

Evidence & guidelines

Explicit criteria for potentially inappropriate medication use in older adults - originating with the Beers criteria and maintained in updated form by professional bodies - translate the toxicological evidence into an appraisable list, while reviews of age-related pharmacokinetics and pharmacodynamics and systematic reviews of anticholinergic burden provide the underlying evidence.

History

Concern about drug toxicity in older adults grew with the ageing of populations and the recognition that standard adult dosing did not account for declining organ function. Mark Beers's explicit criteria, first published in 1991 for nursing-home residents and repeatedly updated since, provided a structured way to identify medications best avoided in older adults, and reviews of age-related pharmacology supplied the mechanistic basis for the field.

Debates

How should potentially inappropriate medication criteria be used?

Explicit lists improve recognition of risky prescribing but are debated as blunt instruments that may not fit every patient's context; commentators stress they support, rather than replace, individualized clinical judgement.

Key figures

• Arduino Mangoni
• Stephen Jackson
• Mark Beers

Seminal works

• beers-1991
• mangoni-2003
• ags-2019

Frequently asked questions

Why are older adults more vulnerable to drug toxicity?

Ageing slows the liver and kidney clearance of many drugs so they accumulate, shifts body composition, and can increase tissue sensitivity, while multimorbidity and polypharmacy add interaction and cumulative-burden risk.

What are potentially inappropriate medications?

Drugs whose risks tend to outweigh their benefits in older adults - for example because of excessive sedative, anticholinergic, or bleeding effects - which explicit criteria such as the Beers criteria flag for caution.