Under which condition would a drug product be considered adulterated?

A drug product is considered adulterated when it contains a different active ingredient than what is specified on its label. This condition poses significant health risks as it can lead to unexpected side effects, ineffective treatment, or harmful reactions for patients who rely on accurate labeling for their medications. The integrity of the drug’s formulation is critical for ensuring its safety and efficacy; any deviation in the active ingredient undermines the trust patients and healthcare professionals place in the product.

The other scenarios, while concerning, pertain to different aspects of drug quality or safety. Improper storage conditions and expired products raise issues about the product's effectiveness or safety but do not directly involve misrepresentation of its contents. Additionally, a sterile solution containing microorganisms is certainly a serious concern, especially regarding sterility and potential contamination, but it’s the mislabeling of active ingredients that directly classifies a product as adulterated under regulatory definitions.