Countless American medicine cabinets contain a familiar bottle. It promises pain relief, sleep aids, and restful nights. Its name: Tylenol PM. But according to a health expert, these little blue pills should be examined more closely—especially when taken night after night.

Dr. Ethan Melillo, a pharmacist from Rhode Island, doesn’t mince words. He has openly stated that Tylenol PM is among the medications he strongly opposes—an unusually direct stance in medicine. His concern isn’t the drug’s ineffectiveness, but rather the fact that it is often misunderstood and mistakenly considered harmless simply because it is well-known and available without a prescription.

Tylenol PM: A risky two-component mixture

Tylenol PM is not a single medication. It is a combination of two active ingredients that work together:

Paracetamol, which relieves pain and fever

Diphenhydramine, an antihistamine that causes drowsiness

At first glance, it sounds tempting – pain relief and improved sleep with just one dose. But Dr. Melillo warns that this convenience can mask real risks, especially with frequent or long-term use.

Paracetamol: A silent burden on the liver

Acetaminophen—the same active ingredient as in conventional Tylenol—is one of the most widely used painkillers in the US. It is inexpensive, readily available, and gentler on the stomach than medications like ibuprofen. However, it puts a heavy strain on the liver.

When you take paracetamol, it is metabolized by your liver. This process produces a small amount of a toxic byproduct called NAPQI. Normally, your body neutralizes this toxin with the help of the antioxidant glutathione, thus preventing damage.

The problem arises when this system is overtaxed – particularly through repeated use, high doses, or combination with alcohol – which makes the liver vulnerable.

But if you:

If you take too much paracetamol in one day,
use it regularly over a longer period, or
have low glutathione levels (which can occur with frequent alcohol consumption, malnutrition, or certain illnesses),
the liver may no longer be able to function adequately. The toxic metabolite NAPQI accumulates. It binds to liver cells, damages them, and in severe cases can lead to liver failure.

According to Dr. Melillo, the maximum safe daily dose for most adults is 4,000 milligrams of acetaminophen. This is roughly equivalent to eight Tylenol PM tablets taken within 24 hours. It is surprisingly easy to exceed this limit—especially since acetaminophen is an ingredient in many other over-the-counter medications for colds, flu, or sinusitis.