Which change in a patient's condition would most likely indicate an adverse reaction to Haldol?

An increase in body temperature, particularly the development of a high fever, can indicate an adverse reaction to Haldol, especially in the context of potential neuroleptic malignant syndrome (NMS). NMS is a serious and rare side effect associated with antipsychotic medications like Haldol. It can present with symptoms such as hyperthermia, muscle rigidity, altered mental status, and autonomic instability. The occurrence of a high fever might be one of the first indicators that the patient is experiencing this severe reaction.

Other symptoms of NMS can include elevated creatine kinase levels and leukocytosis, and it typically occurs within the first two weeks of treatment or after dosage increases. Recognizing this change promptly is crucial for patient safety and treatment management.

In contrast, increased energy levels might simply indicate an improvement in mood or psychological status due to the medication's antipsychotic effects. Improved sleep patterns and a stable mood are generally seen as positive outcomes and do not indicate adverse reactions to the medication.