Seniors experience more side effects from medications because the aging body processes drugs fundamentally differently than a younger one does. The kidneys and liver — the two organs responsible for breaking down and eliminating most medications — slow significantly with age, meaning drugs linger longer in the system and accumulate to levels that can become toxic. At the same time, shifts in body composition, reduced blood flow, and heightened sensitivity in the brain and cardiovascular system mean that even a standard dose can hit harder than intended. A 75-year-old woman prescribed a common sleep aid, for instance, may experience confusion, falls, or prolonged sedation that her physician did not anticipate because the dose was calibrated for a younger physiology.
The problem is compounded dramatically by the sheer number of medications most older adults take. Roughly 90 percent of seniors take at least one prescription drug regularly, and more than a third take five or more — a threshold clinicians define as polypharmacy. Each additional drug multiplies the opportunity for interactions, side effects, and dosing errors. This article covers the physiological reasons seniors are more vulnerable, why polypharmacy sits at the center of the crisis, how inappropriate prescribing makes things worse, and what can realistically be done about it.
Table of Contents
- How Does the Aging Body Change the Way Medications Work?
- What Is Polypharmacy and Why Is It the Core Driver of Medication Side Effects in Seniors?
- Which Medications Are Most Likely to Cause Problems in Older Adults?
- What Can Caregivers and Families Do to Reduce Medication Risks in Seniors?
- How Does Inappropriate Prescribing Make the Problem Worse?
- Why Are Women More Vulnerable to Adverse Drug Reactions in Old Age?
- Where Is Research and Policy Headed on Medication Safety for Older Adults?
- Conclusion
- Frequently Asked Questions
How Does the Aging Body Change the Way Medications Work?
The pharmacological term for how the body handles a drug — absorbing it, distributing it, metabolizing it, and excreting it — is pharmacokinetics. In older adults, every stage of this process is altered. Kidney function declines steadily with age; by the time a person reaches their seventies, glomerular filtration rate may be half of what it was at thirty. The liver, similarly, becomes less efficient at processing drug compounds. The result is that medications clear the body more slowly, raising the risk of accumulation and toxicity even at doses considered safe for the general population. Body composition changes compound the issue. Older adults typically carry more fat relative to lean muscle mass and have lower total body water.
Fat-soluble drugs — including many sedatives and antidepressants — distribute more widely and stay in the system longer. Water-soluble drugs reach higher concentrations in the blood because there is less fluid to dilute them. Reduced cardiac output also slows drug delivery to and from organs, further disrupting expected timing. These are not minor deviations; they can shift the effective dose of a medication by a clinically meaningful margin. Beyond how drugs move through the body, pharmacodynamics — how the body responds to drugs at the target site — also shifts with age. The aging brain becomes more sensitive to sedatives, opioids, and anticholinergic drugs. The cardiovascular system responds more unpredictably to blood pressure medications. Age-related decline in acetylcholine activity is a particular concern: acetylcholine is critical for memory and cognition, and when anticholinergic drugs (used to treat bladder problems, allergies, and depression, among other conditions) are added, the resulting suppression of this already-diminished system can produce delirium, cognitive decline, and acute confusion — especially in someone who already has dementia or is at risk for it.
What Is Polypharmacy and Why Is It the Core Driver of Medication Side Effects in Seniors?
Polypharmacy is defined as the regular use of five or more medications daily. It is not a fringe scenario — it is the norm for a substantial share of older adults. According to Johns Hopkins Medicine, more than 36 percent of adults over 60 take five or more prescription medications. At that threshold and beyond, the likelihood of adverse drug reactions rises steeply, not in a linear fashion but exponentially, because each new drug interacts with the existing regimen in ways that are often impossible to fully predict. The most common adverse outcomes associated with polypharmacy are neuropsychological effects such as delirium, acute kidney failure, and hypotension — low blood pressure that causes dizziness and falls. Falls among older adults are already a leading cause of serious injury and hospitalization, and polypharmacy-related hypotension and sedation are significant contributors.
The risk is not evenly distributed: women and those taking ten or more medications daily — a category called hyperpolypharmacy — face substantially higher rates of adverse drug reactions and hospitalization than their counterparts. It is worth noting that polypharmacy is not always inappropriate. Many older adults have multiple legitimate chronic conditions — diabetes, hypertension, heart disease, arthritis — each requiring its own treatment. The problem arises when the management of drug interactions and cumulative side effects falls behind the pace of prescribing. A person may be prescribed a blood pressure medication that causes dizziness, then a second drug to counteract the dizziness, then a third for a side effect of the second. This prescribing cascade is a well-documented phenomenon, and it results in patients taking drugs whose original purpose has become untraceable within their current regimen.
Which Medications Are Most Likely to Cause Problems in Older Adults?
Not all drug classes carry equal risk in older adults. The American Geriatrics Society’s Beers Criteria — a widely used clinical reference updated regularly — identifies specific medications that are considered potentially inappropriate for older patients because their risks outweigh their benefits in this population. These include certain antihistamines (like diphenhydramine, found in common over-the-counter sleep aids), benzodiazepines, muscle relaxants, and some antidepressants. Despite these warnings, research consistently finds that between one in seven and one in four older patients receive at least one of these flagged medications. A 2025 systematic review published in JAMA Network Open confirmed that potentially inappropriate medication use is highly prevalent worldwide among older adults — not a problem isolated to any one healthcare system or country. This is a structural failure, not an individual one.
Patients may not know their medications are flagged as problematic, and the prescribing physician may not have the full picture of what other clinicians have already prescribed. Specialists routinely prescribe within their domain without visibility into the patient’s broader medication burden. Anticholinergic drugs deserve particular attention on a dementia care platform. These medications — prescribed for conditions as common as overactive bladder, hay fever, and mild depression — suppress the cholinergic system that is already compromised in Alzheimer’s disease and other dementias. Research has associated heavy anticholinergic burden with accelerated cognitive decline and increased dementia risk. For someone already navigating cognitive impairment, exposure to these drugs can dramatically worsen confusion, memory, and daily function in ways that are sometimes mistaken for disease progression rather than a drug effect.
What Can Caregivers and Families Do to Reduce Medication Risks in Seniors?
The most practical protective step is maintaining a complete, current medication list — including over-the-counter drugs, vitamins, and supplements — and bringing it to every medical appointment. Drug interactions do not distinguish between prescription and non-prescription products. St. John’s Wort, for example, interacts with anticoagulants and antidepressants. Aspirin combined with blood thinners raises bleeding risk. Caregivers who assume that only prescription drugs matter may miss half the picture.
A medication review with a pharmacist or geriatrician is one of the highest-value interventions available. These professionals are trained to identify drug-drug interactions, flag Beers Criteria medications, and recommend deprescribing — the deliberate, supervised reduction or elimination of medications that are no longer necessary or are causing more harm than good. The National Institute on Aging and geriatric medicine specialists have increasingly advocated for deprescribing as a standard part of elder care, not an exceptional measure. The tradeoff is real, however: stopping a medication abruptly without supervision can cause rebound effects or withdrawal, so deprescribing must be done carefully and with physician oversight. Families should also be cautious about the assumption that more treatment is always better. The instinct to address every symptom and every risk factor with a corresponding drug is understandable, but in older adults with multiple conditions, aggressive polypharmacy can itself become the primary threat to quality of life. Asking a prescribing physician the direct question — “Is this medication still necessary given everything else my parent takes?” — is a reasonable and appropriate part of advocating for an older adult’s care.
How Does Inappropriate Prescribing Make the Problem Worse?
Inappropriate prescribing in older adults is not a matter of carelessness by individual physicians. It reflects structural pressures: short appointment windows, fragmented records across multiple specialists, limited geriatric training in general medicine, and the genuine complexity of treating someone with five or six concurrent conditions. That said, the scale of the problem is significant. Research reviewed by the National Institutes of Health and reflected in Healthy People 2030 federal objectives has identified inappropriate medication use in older adults as a public health priority, not merely a clinical footnote. Healthy People 2030 — the federal government’s health objectives framework — has set a specific, measurable goal to reduce the proportion of older adults who use inappropriate medications.
That a national health policy initiative has been built around this issue signals how embedded the problem is. The baseline data suggest that current rates of inappropriate prescribing are not marginal; they are common enough to require systemic intervention. A warning worth emphasizing: medication appropriateness can change over time. A drug that was reasonable to prescribe at age 65 may become inappropriate by age 80 as kidney function, cognitive status, and overall frailty evolve. Medication regimens that are never revisited tend to accumulate drugs that no longer serve their original purpose or that now carry risks that did not exist when they were first added. Routine medication reviews — ideally annually or after any major health change — are essential precisely because an older adult’s relationship to each drug in their regimen shifts as they age.
Why Are Women More Vulnerable to Adverse Drug Reactions in Old Age?
Research on adverse drug reactions in older adults has consistently identified female sex as an independent risk factor. Women experience higher rates of adverse drug reactions associated with polypharmacy and hospitalization compared to men, even after accounting for the number of medications taken. Part of this reflects differences in body composition — women generally have a higher fat-to-lean ratio, which alters how fat-soluble drugs are distributed — and differences in baseline kidney function and drug metabolism. Hormonal changes following menopause also shift how certain drug classes are processed.
There is also a prescribing dimension. Historically, women were underrepresented in clinical drug trials, meaning standard dosing recommendations were developed largely on male physiology. The downstream effect is that some standard doses may be disproportionately high for women, contributing to higher adverse event rates. This is an active area of pharmacological research, and awareness of it is relevant for caregivers and patients asking why a prescribed dose may not be working as expected or is producing unexpected side effects.
Where Is Research and Policy Headed on Medication Safety for Older Adults?
The trajectory of both research and healthcare policy points toward more individualized, age-conscious prescribing. Geriatric pharmacology — the specialty focused on how aging changes drug behavior — is receiving greater attention in medical education and clinical guidelines. The Beers Criteria is updated regularly to reflect new evidence. Deprescribing protocols are being studied and implemented in hospital systems.
Electronic health records, when properly integrated, offer the potential to flag dangerous interactions across prescribers in real time. The challenge is translating research consensus into routine clinical practice at scale. Fragmented care — where a cardiologist, a neurologist, a primary care physician, and a urologist may each prescribe without full knowledge of what the others have ordered — remains the default for many older adults with complex conditions. Until medication management is treated as a coordinated discipline rather than a byproduct of specialty care, the gap between what is known about drug safety in older adults and what actually happens in clinical settings will persist. For families and caregivers, awareness of that gap is itself protective.
Conclusion
Seniors experience more medication side effects because aging fundamentally changes how the body absorbs, processes, and responds to drugs — and because most older adults are managing those changes while taking multiple medications simultaneously. Slowed kidney and liver function, altered body composition, heightened brain sensitivity to sedatives and anticholinergic drugs, and the compounding risk of polypharmacy create a pharmacological environment that bears little resemblance to the one in which most drugs were tested and dosed. Between one in seven and one in four older patients are prescribed medications that clinical guidelines specifically flag as inappropriate for their age group, and the consequences — delirium, falls, kidney injury, hospitalization — are well documented and preventable.
The most actionable steps for anyone supporting an older adult are straightforward even if they require persistence: maintain a complete and current medication list, request periodic medication reviews from a pharmacist or geriatrician, and ask directly whether each drug in a regimen is still necessary. Deprescribing, done carefully under supervision, is a legitimate and increasingly encouraged medical intervention. For those caring for someone with dementia or cognitive decline, vigilance around anticholinergic medications in particular is critical — these are common, frequently overlooked, and capable of meaningfully worsening cognitive function in ways that can be reversed if caught in time.
Frequently Asked Questions
What does “polypharmacy” mean, and when does it become dangerous?
Polypharmacy refers to taking five or more medications daily. At this threshold, the risk of adverse drug reactions, falls, and hospitalization rises significantly. Taking ten or more medications — hyperpolypharmacy — carries even greater risk and is associated with acute kidney injury, delirium, and dangerously low blood pressure.
How can I tell if a medication is inappropriate for an older adult?
The American Geriatrics Society’s Beers Criteria is the primary clinical reference for identifying medications that are generally considered unsafe or inappropriate for older adults. A pharmacist or geriatrician can review a medication list against this and similar criteria and recommend alternatives or deprescribing where appropriate.
Is it safe to stop a medication if I think it’s causing side effects?
No — stopping a medication without medical supervision can cause withdrawal effects or rebound symptoms, depending on the drug. Always consult a physician before discontinuing any prescription medication. Supervised deprescribing, with a gradual taper where needed, is the recommended approach.
Why are anticholinergic drugs particularly risky for people with dementia?
Anticholinergic drugs suppress acetylcholine activity in the brain. Because acetylcholine is already reduced in dementia — especially Alzheimer’s disease — adding anticholinergic medications can dramatically worsen memory, cause confusion, and accelerate functional decline. These drugs are found in common over-the-counter products including sleep aids and allergy medications.
Why do women seem to experience more adverse drug reactions than men?
Women have different body composition, kidney function, and drug metabolism compared to men, and historically have been underrepresented in clinical drug trials — meaning standard doses were often calibrated on male physiology. Research consistently identifies female sex as an independent risk factor for adverse drug reactions in older adults.
What is deprescribing, and should I ask my parent’s doctor about it?
Deprescribing is the supervised reduction or elimination of medications that are no longer necessary, are causing harm, or whose risks outweigh their benefits. It is a recognized clinical practice increasingly recommended in geriatric care. Asking a primary care physician or geriatrician to review and potentially simplify a complex medication regimen is a reasonable and often beneficial step.
