Which of the following is an adverse effect of acetaminophen?

Acetaminophen, while widely used as a pain reliever and fever reducer, can lead to renal failure, particularly when taken in excessive doses or in patients with pre-existing kidney issues. This adverse effect is related to the way acetaminophen is metabolized in the liver; under conditions of overdose or certain health conditions, toxic metabolites can accumulate, leading to kidney damage. The kidneys are responsible for filtering and excreting drugs and their metabolites, and when they are adversely affected by substances like acetaminophen, renal function can decline, potentially resulting in acute renal failure.

The other options, while they may be associated with various medications or conditions, are not typically directly linked to acetaminophen use. For example, elevated blood pressure is more associated with NSAIDs rather than acetaminophen, mild gastrointestinal irritation is common with anti-inflammatory drugs, and pneumonia is not a known adverse effect related to acetaminophen. Understanding these nuances is crucial for safe medication practices and recognizing when further medical attention might be necessary.