The Buprenorphine Paradox: How Buprenorphine Triggers and Resolves Opioid Withdrawal.

Buprenorphine (BUP) offers a therapeutic approach for opioid use disorder (OUD) due to its unique pharmacodynamic properties, primarily as a partial agonist with high affinity for the mu-opioid receptor (MOR). BUP's partial agonism and ceiling effect on respiratory depression enhance its safety profile. However, BUP can induce precipitated withdrawal when administered after a full agonist, leading to severe withdrawal symptoms. This Perspective builds on prior work that has linked BUP's high-affinity partial agonism to precipitated withdrawal and low-dose induction strategies. We focus on how BUP's capacity to promote MOR externalization, together with its activity at the nociceptin opioid peptide (NOP) receptor, can help explain why it precipitates withdrawal when administered in the presence of full agonists yet relieves withdrawal once spontaneous withdrawal has begun. Understanding these mechanisms is critical for optimizing BUP protocols in OUD treatment and informs the potential development of new biased MOR agonists (i.e., ligands that preferentially activate specific signalling pathways) for addiction therapy.