Table 1 Defining criteria for groups 1 and 2 at the time of recruitment

Fully adherent to daily OAT in the 3-month period prior to study initiation, defined as:

• No episodes of treatment drop-out (≥ 3 missed consecutive doses), and

• No recorded concerns regarding missed doses by the pharmacy or clinic dosing team

AND

Responding to daily OAT in the 3-month period prior to study initiation, defined as:

• No on-top drug use detected by UDS or self-reporting

Not currently receiving treatment with daily OAT or poor adherence to treatment in the 3-month period prior to study initiation. Poor adherence defined as:

• One or more recorded episodes of treatment drop-out (≥ 3 missed consecutive doses), or

• Concerns had been recorded by the pharmacy or clinic dosing team regarding missed doses

AND/OR

Lack of response to daily OAT in the 3-month period prior to study initiation, defined as:

• On-top drug use detected by either UDS or self-reporting