Breast cancer is the most frequent type of cancer and the second leading cause of cancer-related mortality in women. Mastectomies remain a key component of the treatment of non-metastatic breast cancer, and strategies to treat acute postoperative pain, a complication affecting nearly all patients undergoing surgery, continues to be an important clinical challenge. This study aimed to determine the impact of intraoperative methadone administration compared to conventional short-acting opioids on pain-related perioperative outcomes in women undergoing a mastectomy.

This single-center retrospective study included adult women undergoing total mastectomy. The primary outcome of this study was postoperative pain intensity on day 1 after surgery. Secondary outcomes included perioperative opioid consumption, perioperative non-opioid analgesics use, duration of surgery and anesthesia, time to extubation, pain intensity in the postanesthesia care unit (PACU), anti-emetic use in PACU, and length of stay in hospital. We used the propensity score-based nearest matching with a 1:3 ratio to balance the patient baseline characteristics.

133 patients received methadone, and 2192 patients were treated with short-acting opioids. The analysis demonstrated that methadone was associated with significantly lower intraoperative and postoperative opioid consumption as measured by oral morphine equivalents and lower average pain intensity scores in the postanesthesia care unit. Moreover, methadone was also shown to reduce the use of non-opioid analgesia during surgery.

Our study suggests that the unique pharmacological properties of methadone, including a short onset of action when given intravenously, long-acting pharmacokinetics, and multimodal effects, are associated with better acute pain management after a total mastectomy.