451: Intrathecal Opioid Rotation: Asymmetric Cross-Tolerance and Conversion Ratios

Topic: Clinical Science
Subtopic: Pain category (ICD-11), Chronic cancer related pain, Pharmacological treatments, Pain in Special Populations , Treatment/management

Background and Aims: To investigate the conversion ratios, indications, and clinical outcomes of intrathecal opioid rotation in patients with chronic refractory pain.

Methods: We retrospectively reviewed patients with chronic refractory pain who received a SynchroMed II intrathecal drug delivery system (Medtronic, Minneapolis, MN, USA) at the Department of Pain Medicine, China–Japan Friendship Hospital, between January 2020 and September 2025. Patients who subsequently underwent intrathecal opioid rotation were included. Variables including pain characteristics, indications for rotation, timing, conversion ratios, and post-rotation outcomes were assessed.

Results: A total of 23 patients were included, comprising 18 patients with cancer-related pain and 5 with non-cancer pain. The mean initial conversion ratio from hydromorphone to morphine was 3.25, whereas the corresponding ratio from morphine to hydromorphone was 7.50. At the effective analgesic dose, the corresponding conversion ratios were 3.70 and 5.75, respectively. In patients rotated from morphine to morphine combined with sufentanil, the initial morphine-to-sufentanil conversion ratios were 3600, 1330, and 2000, with corresponding effective analgesic ratios of 3180, 350, and 1310, demonstrating marked interindividual variability. Among the 22 patients who underwent opioid rotation for inadequate analgesia, pain did not improve significantly in 2 patients (both with central pain); satisfactory analgesia was achieved in the remaining 20. One patient underwent rotation due to opioid-related edema; the edema resolved following rotation to hydromorphone.

Conclusions: Intrathecal opioid rotation is an effective strategy to improve analgesic efficacy and to manage opioid-related adverse effects (e.g., edema) in patients with chronic refractory pain. Asymmetric cross-tolerance exists between morphine and hydromorphone. When rotating from morphine to a morphine–sufentanil combination, substantial interindividual variability should be anticipated, and a conservative initial conversion ratio is recommended.

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Presenting Author: Anxiang Liu
Submitting Author: Anxiang Liu

Senior Author: Peng Mao

IASP 2026 Global Year theme of Neuropathic Pain: No

• Bifa Fan: Master of Medicine - Department of Pain Medicine, China–Japan Friendship Hospital
• Ke MA - Beijing University of Chinese Medicine
• Qintian He - China-Japan Friendship Institute of Clinical Medical Sciences
• Yi Zhang - Department of Pain Medicine, China–Japan Friendship Hospital
• Yifan Li - Department of Pain Medicine, China–Japan Friendship Hospital
• Wei Wang - Department of Pain Medicine, China–Japan Friendship Hospital
• Peng Mao: PhD in Medicine - Department of Pain Medicine, China–Japan Friendship Hospital