Is offering this incentive to Derek ethically permissible?

Derek is a 49-year-old man diagnosed with schizoaffective disorder. He has lost his job as a teacher and now lives on the streets after declining to stay in supported housing. He was recently hospitalized for an acute infection and received antipsychotic medication while he stayed at the hospital. His symptoms of delusions and paranoia reduced and his affect improved significantly. Upon discharge from the hospital, Derek did not agree to live in supported housing, but agreed to continue receiving antipsychotic medication through depot injections. Derek was assigned a peer support worker to help him remember when it is time to receive his injections, but he has been showing up irregularly. The mental health team notices that Derek’s delusions are worsening and that he has become increasingly paranoid and agitated. A social worker on the team is concerned about Derek’s ongoing care and suggests that the team offer him a $20 Safeway gift card every time he receives his depot injection.

Is offering this incentive to Derek ethically permissible?