Conversion from parenteral to oral methadone.

The described ratio for methadone conversion from oral route (PO) to parenteral route (PAR) is 2:1 and from PAR to PO is 1:2. Frequently, good control of pain with methadone is PR to PO. We use methadone as a function of opioid rotation and not in the context of mortality outcome and we have noted that the traditional ratio produces toxicity problems. We present our experience with patients who we converted from PAR to PO methadone and we recommend a conversion ratio of 0.7 (PO:PAR = 1:0.7), which approximates the bioavailability of the drug administered orally.