This is an academic paper that evaluations an intervention to reduce unused prescription opioids by buying them back in a VA hospital. A small financial incentive ($5 per pill/$50 max) resulted in 30% of eligible patients returning unused prescription opioids.
Liu, J.Y., Anderson, J.C., Franklin, J.S., Gesek, F.A., Soybel, D.I. (2021). Nudging patients and surgeons to change ambulatory surgery pain management: Results from an opioid buyback program. Surgery, S0039-6060(21), 00034-9.