Which of the following drugs increases the risk of hepatotoxicity when taken with acetaminophen?

The correct answer is alcohol because its consumption can significantly enhance the hepatotoxic risk associated with acetaminophen. Acetaminophen is metabolized in the liver, and excessive intake can lead to liver damage, especially when combined with substances that are also processed in the liver. Alcohol, particularly when consumed in amounts that lead to chronic use or acute intoxication, can induce certain liver enzymes. This induction can cause an increase in the toxic metabolite of acetaminophen, leading to a higher chance of liver injury.

In contrast, the other substances listed do not exhibit the same level of hepatotoxic interaction with acetaminophen. For instance, ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) that primarily poses its own risks, such as gastrointestinal issues or kidney damage, rather than increasing acetaminophen's toxicity. Warfarin, an anticoagulant, and ciprofloxacin, an antibiotic, do not have pharmacological interactions with acetaminophen that elevate the risk of liver toxicity. Therefore, alcohol stands out as the substance that notably heightens the potential for liver damage when taken alongside acetaminophen.