Medication Side Effects in Elderly Patients: Why Age Changes How Drugs Affect the Body

When you’re 70, a simple pill can do more than heal-it can make you dizzy, confused, or even cause a fall. That’s not rare. In fact, elderly medication side effects are one of the most common reasons older adults end up in the hospital. And it’s not because they’re taking too many pills by accident. It’s because their bodies handle drugs differently now than they did at 40.

Why Older Bodies React Differently to Medicines

Your liver and kidneys don’t work the same way after 65. Blood flow to the liver drops by 30-40% between ages 25 and 75. Kidneys filter blood more slowly, losing about 0.8 mL per minute every year after 40. That means drugs stick around longer. Take diazepam, for example. In a 30-year-old, it clears in about 24 to 48 hours. In someone over 70? It can linger for days. That’s why sedatives and sleep aids often leave older adults groggy, unsteady, or disoriented the next morning.

Body composition changes, too. Fat increases while muscle and water decrease. That shifts how drugs spread through the body. Fat-soluble drugs like some antidepressants or antipsychotics build up in fatty tissue and release slowly-leading to unexpected buildup over time. Water-soluble drugs, like lithium or some diuretics, become more concentrated because there’s less water to dilute them.

These aren’t minor tweaks. They’re fundamental changes that turn a safe dose for a 50-year-old into a dangerous one for a 75-year-old.

The Big Risk: Taking Too Many Pills

Most older adults aren’t on one or two meds. They’re on five, seven, even ten. That’s called polypharmacy-and it’s the #1 driver of bad reactions. Each extra pill adds a new chance for interactions. Take a common combo: an NSAID like ibuprofen for arthritis, plus a blood thinner like warfarin. Together, they can spike the risk of a bleeding stomach ulcer by 15 times compared to someone taking neither.

Corticosteroids mixed with NSAIDs? Same problem. SSRIs (common antidepressants) plus certain painkillers? That can trigger a dangerous drop in sodium levels. Even something as simple as St. John’s Wort, a popular herbal supplement, can interfere with heart meds, blood thinners, and antidepressants.

It’s not just drug-drug interactions. It’s drug-disease clashes. For instance, glyburide-a diabetes pill-can cause dangerously low blood sugar in seniors because their bodies can’t bounce back as easily. Sliding-scale insulin, often used in hospitals, can lead to wild swings in glucose levels and is now flagged as risky for older adults at home.

Side Effects You Might Not Recognize

In younger people, side effects are obvious: nausea, rash, diarrhea. In older adults? They’re sneaky. You might think your mom is just getting forgetful. But what if it’s the anticholinergic in her bladder medication? Or her blood pressure pill is making her dizzy when she stands up? That’s orthostatic hypotension-and it’s a top cause of falls.

Falls are terrifying. One in three seniors falls each year. And 20-30% of those falls are directly tied to medications. Sedatives, antipsychotics, even some heart meds can throw off balance. Confusion? That’s not just aging. It could be a reaction to pentazocine, an opioid that’s more likely to cause hallucinations in older brains. Weight loss? Could be an under-the-radar side effect of an antidepressant or a thyroid med.

These aren’t “normal” signs of getting older. They’re red flags.

The Beers Criteria: A Lifesaving Checklist

Since 1991, doctors have used the Beers Criteria-a list of medications that are risky for older adults. Updated in 2012 and again in 2019, it’s the most trusted tool in geriatric care. It doesn’t say “never use these.” It says: “Use with extreme caution-or avoid altogether-if you’re over 65.”

Here’s what’s on the list:

• Propoxyphene (no longer sold in the U.S., but still found in old prescriptions)-minimal pain relief, high risk of confusion.
• Indomethacin-an NSAID with the highest rate of brain-related side effects in seniors.
• Phenylbutazone-can wipe out blood cell production.
• Megestrol (Megace)-used for appetite, but increases risk of blood clots and death.
• Acetylcholinesterase inhibitors-like donepezil for Alzheimer’s-can slow the heart too much in people with existing slow heart rates.
• Glitazones (pioglitazone, rosiglitazone)-worsen heart failure.
• SSRIs in patients with a history of falls or fractures-can lower sodium and increase bleeding risk.

These aren’t random picks. Each one has been studied in real older patients. The data shows clear harm.

What to Do: A Practical Plan

You don’t have to stop all meds. But you need to question them. Here’s how:

1. Keep a full list-every prescription, over-the-counter pill, vitamin, herb, or supplement. Include doses and why you take them.
2. Bring it to every appointment-not just your doctor’s. Bring it to the pharmacist, the physical therapist, the specialist.
3. Ask: “Is this still necessary?” Every six months, review each med with your doctor. Can one be stopped? Can a lower dose work?
4. Watch for new symptoms-if you start feeling foggy, off-balance, or unusually tired after starting a new drug, don’t wait. Call your provider.
5. Use a pill organizer-but make sure it’s paired with someone who checks it. Cognitive decline or vision problems make self-management risky.

Pharmacists are your secret weapon. In the UK and U.S., medication therapy management (MTM) services are available for seniors on multiple drugs. These are free or low-cost consultations where a pharmacist reviews your entire list, spots interactions, and suggests safer alternatives.

When Less Is More

Deprescribing isn’t giving up. It’s choosing safety over routine. Studies show that when seniors stop unnecessary meds-like long-term benzodiazepines or proton pump inhibitors taken for years without clear need-they often feel better. Less dizziness. Better sleep. Fewer falls.

One 2021 study followed 1,200 older adults who were gradually taken off four or more unnecessary drugs. Within six months, 40% reported improved energy. 30% had fewer falls. Hospital visits dropped by nearly half.

It’s not about cutting meds just because they’re on the Beers list. It’s about matching the drug to the person. A 72-year-old with severe arthritis might still need an NSAID-just not at the highest dose. A 80-year-old with mild depression might do better with therapy and exercise than with an SSRI that makes them unsteady.

The Bigger Picture

By 2030, one in five Americans will be over 65. That’s 95 million people. Right now, 10-23% of hospital admissions in this group are due to bad drug reactions-and half of those are preventable. The cost? Around $3.5 billion a year in the U.S. alone.

Health systems are starting to respond. Medicare now tracks “potentially inappropriate prescribing” as part of its quality metrics. Hospitals are hiring geriatric pharmacists. Clinics are using electronic alerts when a doctor tries to prescribe a Beers-listed drug to someone over 70.

But real change happens at the kitchen table. It happens when a daughter asks, “Why are you still taking that sleeping pill?” Or when a grandpa tells his doctor, “I’ve been falling more since I started that new blood pressure med.”

Medications save lives. But they can also steal them-if we don’t pay attention to how aging changes the rules.