In my institution, Donostia University Hospital, the most common epidural mixture is Bupivacaine 0,125% plus fentanyl 2 micrg/ml, but in some cases 20-40 micrg/ml of morphine is added to the same Local anesthetic concentration, both prepared under steryl conditions by the pharmacy service. Methadone, as epidural bolus of 3 mg/8 h is often used after gynaecological surgery, or as a single bolus (3-5 mg) after removing epidural catheter after caesaean surgery.

We used it routinely (I was in the Navy and am currently retired). The choice of drug depends upon where the surgery is and where the catheter tip is. I used to prefer putting the catheter tip near the surgery incision central dermatome level as this minimized the drug requirements and complications (urinary retention). We also avoided local anesthetic due to the risk of causing muscle weakness, postural hypotension, and folls. So, for a thoracic surgery a catheter at T4-6 would work great with fentanyl as the drug as it doesn't migrate far. If the catheter is lumbar a drug like morphine is necessary so it migrates to the level required. No experience with epidural methadone but they all work the same. Only difference is how much they migrate due to their lipid binding.