Rethinking a Common Household Remedy: Doctors Call for Scrutiny of Diphenhydramine
A familiar sight in medicine cabinets across Singapore and beyond, diphenhydramine, the active ingredient in popular brands like Benadryl, is facing increasing scrutiny from medical professionals. Widely used by both adults and children for managing allergy symptoms such as runny noses, sneezing, itchiness, and watery eyes, it’s also a go-to for its potent drowsy effect, often employed to aid sleep. However, a growing chorus of physicians argues that the risks associated with this over-the-counter (OTC) stalwart may be significantly outweighing its benefits.
Internal medicine specialists are advocating for a re-evaluation of diphenhydramine’s accessibility, suggesting that its presence on pharmacy shelves warrants reconsideration due to concerns about potentially severe adverse effects. Among these are worries about significant neurological impacts.
Understanding Diphenhydramine’s Mechanism and Risks
Diphenhydramine belongs to a class of medications known as first-generation antihistamines. A key characteristic of these drugs is their ability to readily cross the blood-brain barrier. Once in the brain, diphenhydramine exerts its well-known sedative effects, leading to pronounced drowsiness, reduced alertness, and impaired coordination. This sedation can have tangible consequences, impacting work productivity, academic performance in students, and critically, increasing the risk of motor vehicle accidents. In some studies, the driving impairment caused by diphenhydramine has been found to be more severe than that experienced at or above the legal alcohol limit.
Beyond the pervasive sleepiness, diphenhydramine can trigger a spectrum of other uncomfortable and, in some instances, hazardous side effects. These include dry mouth, constipation, blurred vision, confusion, and difficulties with urination. These particular effects pose a heightened risk for older adults, whose bodies may be less resilient to such side effects. Alarmingly, even younger individuals have been found to overdose on this medication, which is often perceived as relatively benign.
Long-Term Concerns and Safer Alternatives
The implications of frequent or long-term use of diphenhydramine are also a significant concern. Research has indicated potential links to serious heart rhythm abnormalities and an elevated risk of developing dementia. The sedative properties are considered so pronounced that regulatory bodies in Europe advise against driving after taking the medication, and aviation authorities prohibit its use by pilots during flight.
In contrast, newer generations of antihistamines, such as fexofenadine (found in Allegra) and loratadine (found in Claritin), have emerged. Developed in the latter half of the 20th century, these second-generation antihistamines offer comparable relief for allergy symptoms but are formulated to minimise side effects, particularly drowsiness, and provide longer-lasting action. Despite their advantages, comparable pricing, and OTC availability, diphenhydramine continues to be a popular choice, partly due to its inclusion in a vast array of products targeting allergies, common colds, and sleep disturbances.
Expert Opinions and Regulatory Questions
Physicians from prestigious institutions like the Johns Hopkins University School of Medicine and the University of California, San Diego, have articulated their concerns in the medical journal JAMA Internal Medicine. They argue that diphenhydramine should be phased out in favour of second-generation antihistamines, including those like fexofenadine and desloratadine (the active ingredient in Clarinex).
The proponents of this shift highlight that “widespread advertisements, entrenched prescribing habits, and self-treatment behaviours developed over decades contribute to the persistent use of diphenhydramine.” However, they strongly contend that “OTC availability is the major contributor to the widespread use of diphenhydramine, the under-recognition of adverse effects, and the false perception of safety.”
For a drug to be available over-the-counter, it is generally understood to be safe and effective for its intended use. When new safety concerns surface, regulatory bodies like the Health Sciences Authority (HSA) in Singapore, or the FDA in the US, have the authority to convene expert panels to review the evidence and potentially recommend the removal of a product from the market.
The ‘Benadryl Challenge’ and its Tragic Consequences
The potential dangers of diphenhydramine were starkly illuminated by the emergence of the “Benadryl Challenge” on social media platforms. This dangerous trend saw young people encouraging each other to consume dangerously high doses of diphenhydramine in an attempt to induce hallucinations.
Kenvue, the manufacturer of Benadryl, has stated that “the health and safety of people who use our products is our top priority.” They emphasize their commitment to educating consumers on the proper and safe use of their products, including those containing diphenhydramine, and advise users to “carefully read and follow the instructions on the label and contact their health care professional should they have questions.”
The tragic reality of this trend was underscored by the death of Jacob Howard Stevens from Ohio, who passed away after ingesting a significantly higher dose than recommended, leading to immediate seizures and ultimately brain death. Similarly, Cook Children’s Hospital in Fort Worth, Texas, issued a public warning after treating three teenagers for Benadryl overdoses, all of whom reported being influenced by TikTok videos promoting the idea of achieving a high or experiencing hallucinations by taking excessive amounts of the allergy medication.
Link to Cognitive Decline and Rising Healthcare Costs
Beyond acute overdose risks, research from a decade ago has suggested a potential link between the long-term use of anticholinergic medications, including diphenhydramine, and an increased risk of dementia. A significant study published in JAMA Internal Medicine in 2015 followed over 3,400 older adults for seven years. The findings indicated that individuals who frequently used diphenhydramine and other similar antihistamines had a substantially higher risk of developing dementia and Alzheimer’s disease compared to those who did not use these medications.
The physicians advocating for diphenhydramine’s removal from the OTC market also point to the substantial burden it places on healthcare systems. They estimate that the drug contributes to thousands of hospitalizations annually, thereby increasing healthcare-related costs. These costs encompass emergency room visits, hospital admissions, physician consultations, and indirect expenses such as reduced productivity in the workplace and academic settings.
Alarming Increase in Intentional Overdoses
Further data from a 10-year review of poison centre data, published in the journal Pediatrics, revealed a concerning 87 percent surge in intentional diphenhydramine overdoses among children and adolescents. Notably, suicidal intent emerged as the leading cause within this category, more than doubling during the review period. The study highlighted that a vast majority of these cases, around 90 percent, necessitated hospital or clinic treatment, with one in five patients requiring admission to critical care units.
The Future of Allergy Relief
In contrast, newer antihistamines are designed to target allergy symptoms more selectively, with formulations that minimise their ability to cross the blood-brain barrier. This targeted approach significantly reduces the sedative effects commonly associated with older drugs like Benadryl, rendering them “non-impairing” and making them a preferred choice for individuals who need to remain alert and functional during work, school, or while driving.
The researchers advocating for a change in diphenhydramine’s market status believe that patients would benefit and the healthcare system would see cost savings if oral diphenhydramine were no longer available over-the-counter. While acknowledging that making it a prescription-only medication might limit immediate access for some, they argue that “this impact is outweighed by the substantial public health benefits.” They conclude that “The consequence of maintaining the status quo is no longer acceptable.”
