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The parents of a University of Oklahoma sophomore who died from acetaminophen overdose want others to know taking too much Tylenol isn't safe.

Madalyn Byrne, 19, died Monday from liver damage and cardiac arrest from taking too much acetaminophen, the active ingredient in Tylenol and many other commonly used medicines.

She had taken, her parents and physicians estimate, nine extra-strength Tylenol pills a day over three to four weeks. The recommended dose is eight or fewer a day. Her roommate found her on the sofa Sunday morning, disoriented and covered with vomit.

Liver experts at Integris Baptist Medical Center, where the dean’s list student died after her heart stopped, said acetaminophen should be taken cautiously.

Madalyn Byrne’s mother, Evelyn; father, Michael; and aunt, Vicky Sims, spoke Thursday at Baptist about her death.

Too much acetaminophen can cause liver failure. Although doctors can treat overdoses when they catch them early, damage can be fatal if left too long.

Dr. Harlan Wright, chief of hepatology at Nazih Zuhdi Transplant Institute at Baptist, said many people keep taking pills when the pain doesn’t go away. Acetaminophen builds up and begins a metabolic cascade that can poison the liver.

“The sicker your liver gets, the more Tylenol is not metabolized, and you get this whole process,” he said, estimating Madalyn Byrne’s liver likely was damaged several days before she was taken to the hospital.

However, he said, Tylenol has a safe dose of two grams -- that translates to fewer than four extra-strength Tylenol pills.

A mild overdose causes few symptoms. A serious overdose will likely be apparent to doctors when liver tests are run, Wright said.

Madalyn Byrne played the mellophone for the OU marching band. She was majoring in music education and Spanish, hoping to one day teach. She mentored younger students from her Burtonsville, Md., school and lived to play her French horn.

Evelyn Byrne called for acetaminophen bottles to provide a greater explanation of its danger. She described other product labels that are explicit about risks.

“A 19-year-old girl needs to read that bottle and be sure what will happen,” she said.