Randomization
unequal block
Randomization was performed by a blinded member of the investigation team (L.C.) not directly involved with daily study procedures. A computer-generated random number sequence with unequal block randomization (60% intervention, 40% control) was created, stratified by sex, and placed into sequentially numbered opaque envelopes (n = 30/group/sex for a total of 120 random allocations). Group allocation occurred after day 1 assessment and just before the first dose of methadone with an assignment reveal.