Washington ? Think popping extra pain pills can’t hurt? Think again: Accidental poisonings from the nation’s most popular pain reliever seem to be rising, making acetaminophen the leading cause of acute liver failure.

Use it correctly and acetaminophen, best known by the Tylenol brand, lives up to its reputation as one of the safest painkillers. It’s taken by some 100 million people a year, and liver damage occurs in only a small fraction of users.

But it’s damage that can kill or require a liver transplant, damage that frustrated liver specialists insist should be avoidable.

The problem comes when people don’t follow instructions – or unwittingly take too much, not realizing acetaminophen is in hundreds of products, from the over-the-counter remedies Theraflu and Excedrin to the prescription narcotics Vicodin and Percocet.

“The argument that it’s the safest sort of has overruled the idea that people cannot take any amount they feel like,” says Dr. William Lee, of the University of Texas Southwestern Medical Center, who laments that acetaminophen is popped like M&Ms.

Acetaminophen bottles recommend that adults take no more than 4,000 milligrams a day, or eight extra-strength pills.

Just a doubling of the maximum daily dose can be enough to kill, warns Dr. Anne Larson, of the University of Washington Medical Center.

The Food and Drug Administration has long wrestled with the liver risk, warning two years ago that more than 56,000 emergency room visits a year are from acetaminophen overdoses and that 100 people die annually from unintentionally taking too much.

Meanwhile, the advice is simple: Read drug labels and add up all your acetaminophen, avoiding more than 4,000 mg a day. Lee advises no more than 2,000 to 3,000 mg for more vulnerable people, who regularly use alcohol or have hepatitis.