Efficacy of Chronic Morphine in a Rat Model of Cancer-Induced Bone Pain: Behavior and in Dorsal Horn Pathophysiology

Abstract Morphine is one of the main analgesics in cancer-induced bone pain (CIBP). To investigate the efficacy of morphine in CIBP and alteration in dorsal horn pathophysiology, systemic morphine was administered (3 mg/kg) bi-daily between days 11 and 15 after MRMT-1 carcinoma cell injections (compared with a single injection (3 mg/kg) of morphine on day 15, and acute spinal morphine (0.1, 1, 10 μg/50 μL). The chronic systemic morphine schedule significantly attenuated pain behavior (von Frey 15 g; P P Perspective This study confirms the resemblance of the rat model to human CIBP with respect to the efficacy of morphine and further suggests that adjuvant therapy is required to reverse the dorsal horn pathophysiology.