Prolonged-release buprenorphine formulations: Perspectives for clinical practice.

Buprenorphine and methadone are the two main opioid agonist treatments approved for opioid use disorder. Buprenorphine is a partial agonist of the mu opioid receptors, which has been merely available through sublingual form until now. In practice, the use of buprenorphine is smoother than that of methadone, and it induces reduced risks of overdose. However, sublingual buprenorphine also exposes to risks (e.g., withdrawal, misuse) and constraints (e.g., daily intake). Three new galenic formulations of prolonged-release buprenorphine (PRB) are being commercialized and should allow some improvements in patients' comfort and safety. This narrative review aims to describe the main technical features and efficacy and safety data of these PRBs, as well as patients' and professionals' expectancies and concerns, using data of the scientific literature and the regulatory texts. PRBs consist of one subcutaneous implant and two subcutaneous injection depots. Sixmo®/Probuphine® is a six-month-long implant which needs to be surgically placed and removed and is approved for subjects previously treated with a maximum daily dose of 8mg of sublingual buprenorphine, and can be used only for two successive periods of six months before the subject needs to be switched back to sublingual form. Sublocade® is a one-month-long depot formulation that is indicated in switch from sublingual buprenorphine, and which proposes only two dose schemes, i.e., 100 and 300mg monthly. Buvidal®/Brixadi® is a one-week- or one-month-long depot formulation with multiple dosages, which can be used in initiation or in switched from sublingual formulations. While opioid users report some concerns with a risk of coercive use of long-acting forms of buprenorphine, both users and professionals deem that these new specialties could be particularly appreciated in stabilized patients bothered with the daily intake of the treatments, or specific situations at risk of treatment dropout (e.g., following hospital discharge or prison release).