Abstract
BACKGROUND: Morphine is widely used to treat moderate-to-severe cancer pain. However, it causes various adverse effects, with morphine-induced fever being an extremely rare and poorly understood symptom. CASE PRESENTATION: We report the case of a 58-year-old Chinese woman with advanced lung cancer. Due to the ineffectiveness of tramadol for pain relief, her treatment regimen was switched to morphine. Following the change, she developed nausea, vomiting, dizziness, and elevated body temperature. A similar episode occurred subsequently. After a drug review, the pharmacist speculated that morphine was the most likely causative agent. Upon discontinuation of morphine, her body temperature returned to baseline levels. CONCLUSIONS: This case highlights the need for healthcare providers to consider morphine as a potential cause of unexplained fever in patients. The fever may be caused by a hypersensitive response, as there was a significant increase in eosinophils during the fever episodes.