Does cutting heroin with xanax makes it stronger?

Taking xanax with methdone is like doubling the dose of methadone.

Xanax, or alprazolam, is a benzodiazapine, and functions as an anti-anxietal medication. Methadone is a synthetic narcotic, used for pain control and as a substitute for opiates/opioids. These two functions are not the same nor are they synergistic in normal prescribed dosages.

So no -- alprazolam does not make methadone stronger.