Which of the following side effects is associated with Tylenol?

Tylenol, also known as acetaminophen, is primarily metabolized by the liver, and one of the significant concerns with this medication is the potential for liver damage, especially in cases of overdose or prolonged use beyond recommended doses. Dark urine can be an indication of liver dysfunction, as it may suggest elevated levels of bilirubin in the urine due to liver impairment. This side effect becomes particularly relevant when discussing the risks associated with acetaminophen, as liver damage can lead to the excretion of darker urine.

The other options listed are less commonly associated directly with Tylenol. Hallucinations are not a recognized side effect of Tylenol, and while some medications might cause such reactions, acetaminophen is not among them. Constipation is often associated with opioid medications or certain other types of drugs, but not typically with Tylenol. Nausea and vomiting can occur with a variety of medications and conditions but are not specific or distinctive side effects of acetaminophen. Thus, the link between dark urine and potential liver issues makes this choice the most relevant in the context of Tylenol's side effects.