Adherence to Opioid Use Disorder treatment with an extended-release weekly and monthly injectable buprenorphine

Aim: Buprenorphine treatment for Opioid Use Disorder (OUD) success depends on maintaining therapeutic plasma levels. In OUD, physical changes occur to brain areas critical to judgment, decision-making, memory and behavior control, so choosing or remembering to take daily buprenorphine may be an obstacle. Clinical consequences of non-adherence may involve return to non-prescribed opioid use. Prior studies found sublingual buprenorphine adherence to range between 21% and 43%. In the treatment of conditions other than OUD, poor adherence has been associated with increased dosing frequency. Long-acting injectables have been used successfully in difficult-to-treat psychiatric diseases to address adherence challenges. CAM2038, an extended-release buprenorphine, has been available in the US in multiple dosage strengths in weekly and monthly formulations since September 2023. We aimed to evaluate adherence among patients initiating OUD treatment with CAM2038 weekly or monthly.  
Methods: Patients who had received at least two shipments of CAM2038 weekly or monthly between September 5, 2023 and February 23, 2024 and where longitudinal shipment history was available were included in the analysis. Adherence to CAM2038 was determined using the Medication Possession Ratio (MPR), calculated based on total days supplied divided by total days lapsed between product ship dates. MPR for patients initiating treatment with CAM2038 weekly, CAM2038 monthly, and pooled was evaluated.
Results: A total of 4,928 patients met inclusion criteria for the analysis. 1,704 patients were initiated with CAM2038 weekly and 3,224 patients with CAM2038 monthly. The MPR for CAM2038 weekly and monthly was 75% and 94%, respectively. The MPR for the pooled population was 88%.
Conclusion: Both weekly and monthly CAM2038 demonstrated high adherence. Consistent with longer dosing intervals supporting adherence, patients initiating with CAM2038 monthly exhibited higher adherence than patients initiating treatment with CAM2038 weekly.