Understanding the Increased Risk in Older Adults
Age-related physiological changes significantly alter how the body processes and responds to medication. With advancing age, many older adults experience a decline in kidney and liver function, which slows the metabolism and clearance of drugs from the body. This can lead to the accumulation of medication, increasing the risk of toxicity and adverse effects. Additionally, older adults often have multiple chronic health conditions, leading to polypharmacy—the use of multiple drugs simultaneously. This complex medication regimen increases the likelihood of drug-drug interactions and adverse events.
Polypharmacy itself is a major risk factor, as each new medication adds to the potential for interactions. One study found that patients taking five to nine medications have a 50% chance of an adverse drug interaction. It is also common for symptoms caused by an adverse drug event to be mistakenly identified as a new medical condition, leading to another prescription in a cycle known as a 'prescribing cascade'.
Primary Culprits: High-Risk Drug Classes
Psychoactive Medications
Psychoactive drugs, which affect the central nervous system, are heavily implicated in ADEs among older adults. Key examples include:
- Anticholinergics: Found in some antidepressants, antihistamines, and bladder control medications, these drugs block the neurotransmitter acetylcholine, which is critical for cognitive function. Adverse effects include confusion, delirium, falls, and urinary retention. A cumulative measure of anticholinergic exposure, known as the 'anticholinergic burden,' is directly linked to an increased risk of cognitive decline and dementia.
- Benzodiazepines: These are used to treat anxiety and insomnia but are linked to increased risks of cognitive impairment, falls, fractures, and dependence in older adults. Because of their sedative effects and altered metabolism in the elderly, they are generally considered potentially inappropriate medications by the American Geriatrics Society.
- Antipsychotics and Antidepressants: These can also increase the risk of falls and cognitive problems. Certain antipsychotics carry a boxed warning for increased mortality risk in dementia patients.
Anticoagulants and Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)
Medications that affect blood clotting are also high-risk. Anticoagulants like warfarin are frequently involved in serious ADEs, primarily major bleeding episodes, which can be life-threatening. NSAIDs, especially long-acting ones, increase the risk of gastrointestinal bleeding and kidney problems, particularly when combined with anticoagulants or other medications.
Other Significant Drug Classes
- Cardiovascular Drugs: This broad category includes diuretics, beta-blockers, and antiarrhythmics. While essential for treating conditions like heart failure and hypertension, they require careful monitoring. Diuretics can cause dehydration and electrolyte imbalances, while other cardiovascular drugs can cause orthostatic hypotension (sudden drop in blood pressure), leading to falls.
- Hypoglycemics: Medications for diabetes, such as insulin and sulfonylureas, can cause hypoglycemia (low blood sugar), which can be dangerous for older adults. Their narrow therapeutic window necessitates careful dosage adjustments.
The Cumulative Effect: Anticholinergic Burden
The concept of anticholinergic burden is particularly relevant to older adults. It refers to the cumulative effect of taking multiple medications with anticholinergic properties. For example, a person might take an antidepressant (like amitriptyline), an over-the-counter sleep aid (like Benadryl), and a bladder control medication (like oxybutynin). Each drug on its own might have a mild effect, but together, their combined anticholinergic properties significantly increase the risk of confusion, falls, and other serious adverse events. Healthcare providers often use screening tools like the Anticholinergic Risk Scale to assess this burden and identify ways to reduce it.
Preventing Adverse Drug Events
Preventing ADEs in the elderly requires a proactive, systematic approach. This includes:
- Regular Medication Review: A comprehensive review of all medications, including over-the-counter drugs, supplements, and herbals, should be conducted regularly. The 'brown-bag' method, where patients bring all their medications to appointments, is an effective way to facilitate this.
- Start Low and Go Slow: When prescribing a new medication for an older adult, it is a standard practice to start with the lowest possible dose and increase it slowly while carefully monitoring for adverse effects.
- Deprescribing: This is the practice of systematically reducing or stopping medications that may be causing harm or are no longer necessary. The goal is to improve outcomes by reducing the risk of ADEs, which can also decrease the burden of managing multiple pills. For more information on this process, a useful resource is the National Institute on Aging.
Comparative Risks: A Quick Guide to High-Risk Drug Classes
| Drug Class | Examples | Common Adverse Events in Elderly | Increased Risk Due To |
|---|---|---|---|
| Benzodiazepines | Lorazepam, Diazepam, Alprazolam | Cognitive impairment, confusion, falls, fractures, dependence | Increased brain sensitivity, slower metabolism of long-acting agents |
| Anticholinergics | Diphenhydramine, Oxybutynin | Delirium, memory loss, urinary retention, blurred vision | Cumulative effect of multiple drugs, age-related decline in acetylcholine |
| Anticoagulants | Warfarin, Apixaban | Major bleeding episodes (e.g., gastrointestinal, intracranial) | Increased risk with age, potential for drug-drug interactions, fluctuating INR levels |
| NSAIDs | Ibuprofen, Naproxen | Gastrointestinal bleeding, kidney impairment, high blood pressure | Reduced kidney function, concurrent use of other medications like anticoagulants |
| Opioid Analgesics | Morphine, Oxycodone | Sedation, confusion, constipation, respiratory depression | Heightened central nervous system sensitivity |
Conclusion
Understanding which drug classes are commonly associated with adverse drug events in elderly patients—especially psychoactive drugs, anticoagulants, and NSAIDs—is essential for safe and effective healthcare. The heightened risk in older adults is a complex issue driven by physiological changes, polypharmacy, and specific drug properties like anticholinergic effects. By prioritizing regular medication reviews, practicing proactive deprescribing, and following cautious prescribing principles like "start low and go slow," healthcare providers and caregivers can work together to significantly reduce the risk of adverse drug events and improve the overall well-being of older adults.
