^^^ Yep. I'm surprised no one knows this, I mean all opioids are slightly alkaline, so they all prefer a basic environment. But methadone is highly PH dependent. A low stomach PH crushes bioavailability, and low urine PH decreases half-life, as my good friend, Crzydiamond mentioned.
In addition, a very slight decrease in plasma PH increases the amount of free methadone in blood(but please don't mess with the PH of blood!)
So yes, methadone is a spoiled rotten opioid, which whines "I'm synthetic and I don't like acid! WHAAA!!!!"