Methadone Dose Monitoring With a Remote Medication Monitor

The investigator will conduct a non-randomized, non-blinded, feasibility study at a single center in the United States. The study will include up to 20 subjects of an equal number of male and female adults (ages 18-70) who have a prescription for methadone. In Aim 1, the investigators will determine if an RMM can continuously assess the status of taking a prescribed dose of methadone over time, by inserting the dermal ISF sensing elements into the subjects' abdominal skin. Biosample collections (i.e., ISF, blood) and pharmacokinetic monitoring will occur over a 6-hour period. By completing this aim, the investigator will determine if a physician is able to recognize the pharmacokinetic profile of a taken dose of methadone. The physician will see a dosing curve display generated from dermal ISF dialysis fluid sampling using an external fiberoptic sensor system that is worn continuously on the abdomen similar to continuous glucose monitors.