Despite this, Tylenol PM still delivers 500 milligrams of acetaminophen per pill.
Diphenhydramine: Sleep Now, Side Effects Later
The second active ingredient in Tylenol PM is diphenhydramine, better known as Benadryl. This antihistamine is what causes the sedating effect that helps people fall asleep. However, that drowsiness comes with trade-offs—especially when the drug is used regularly rather than occasionally.
While it may make sleep come easier in the short term, repeated use can carry cognitive and neurological consequences that many users never anticipate.
Diphenhydramine belongs to a class of drugs known as anticholinergics, meaning it interferes with the brain chemical acetylcholine. This chemical plays a critical role in memory, learning, and overall cognitive performance.
When acetylcholine is blocked too frequently or over long periods, problems can emerge. Research has found that individuals who used anticholinergic medications daily for three years or more faced a 54% greater risk of developing dementia compared with those who used them only occasionally.
Diphenhydramine can also cause a range of side effects, including:
Dry mouth
Lightheadedness or dizziness
Confusion, particularly in older adults
Urinary retention, which can lead to additional complications in the elderly
Dr. Melillo points out that while these effects may seem mild on their own, they can set off or worsen age-related issues—raising the risk of falls, dehydration, and episodes of delirium.
Tylenol PM and Riskier Choices?
Here’s an unexpected twist: acetaminophen may influence how you feel—and how you judge risk.
In a 2020 study from Ohio State University, participants were given either 1,000 milligrams of acetaminophen or a placebo. They were then asked to evaluate how risky various activities seemed, from skydiving and bungee jumping to major life decisions like changing careers.
De resultaten waren verrassend. Degenen die paracetamol gebruikten, beoordeelden deze activiteiten consequent als minder risicovol dan deelnemers die het medicijn niet hadden gebruikt. Onderzoekers suggereren dat het medicijn emotionele reacties kan dempen en gevoelens zoals angst en opwinding kan verzachten.
