The pain felt after orthopedic surgery in the absence of adequate locoregional anesthesia is often insufficiently controlled, especially during the first 24 hours postoperatively.

Methadone, due to its long half-life, may provide better pain control after orthopedic surgery when associated locoregional anesthesia cannot be performed.

It may be impossible to perform loco-regional anesthesia in various contexts: patient refusal, pre-existing neurological impairment, infection at the injection site, coagulopathies, inability to cooperate, total language barrier, allergy to anesthetics, unavailability of equipment (ultrasound, etc.) or equipped room, lack of experience of nursing staff in performing the block and in the postoperative management of the patient.

Intraoperative administration of methadone in these settings may be superior to sufentanil for pain control during the 24 hours post orthopedic surgery, and the pain control provided by methadone does not appear to imply a higher likelihood of adverse events related to opioids.

Inclusion Criteria:

• Age between 18 and 80 years old
• ASA 1-3 status
• Elective partial or total hip and knee arthroplasty

Exclusion Criteria:

• Patient refusal
• Preoperative renal failure (serum creatinine > 2 mg/dL or 1.5-fold
• Increase in basal plasma creatinine or GFR < 90 ml/min/1.73m2)
• Significant hepatic dysfunction (PT <50% or increase in 3 times basal transaminases)
• Known heart failure
• Preoperative hemodynamic instability (preoperative use of inotropes or vasopressors)
• Known methadone or sufentanil allergy
• Preoperative opioid use or history of opioid abuse
• Pregnancy and breastfeeding.