If an applicant is legally taking an opioid, a drug test should not come across as positive.
However, if you do become aware that an applicant is legally taking an opioid, do not assume that the applicant cannot do the job because of this. Everyone reacts differently to medication, and the employee’s use of opioids may not be a problem.
The applicant is responsible for talking to the prescribing physician or pharmacist about whether or not medication could interfere with job duties. You can talk to the applicant about the job duties and ask if the applicant can perform them with or without reasonable accommodation.