Which of the following is a common sign of drug toxicity?

Altered mental status is a significant indicator of drug toxicity. When a patient experiences toxicity from a medication, it can lead to various neurological symptoms due to the drug's effects on the brain and central nervous system. This can manifest as confusion, drowsiness, agitation, hallucinations, or even coma.

Toxicity typically results from elevated levels of a drug in the bloodstream beyond therapeutic ranges, which can disrupt neurotransmitter function, impair cognitive processes, and alter mood and behavior. Therefore, monitoring a patient's mental status is crucial when assessing potential drug toxicity, as changes can indicate the severity of the situation and guide appropriate interventions.

In contrast, while headaches can occur due to numerous reasons, including side effects of medications or withdrawal, they are not specific enough to indicate drug toxicity. Increased energy and improved appetite typically do not correlate with toxicity; rather, they may suggest absence of side effects or effective treatment. Thus, altered mental status stands out as a clear and concerning sign of potential drug toxicity.