Objectives: To describe 2 case reports in which high-dose administration of sublingual buprenorphine/naloxone quickly stabilized fentanyl users who presented to the hospital. To discuss how early administration of extended-release buprenorphine, before the patient is discharged, may improve retention rates for outpatient buprenorphine treatment. Methods: Two case reports of fentanyl users presented to the emergency department at the general hospital in Timmins, Canada are described. They were rapidly stabilized on high-dose sublingual buprenorphine/ naloxone and then transitioned within 24 to 36 hours to buprenorphine extended-release subcutaneous injection. Results: In both cases, their withdrawal symptoms quickly resolved, without sedation or precipitated withdrawal. Both patients followed up with the outpatient clinic for another injection of extended-release buprenorphine. Conclusions: High-dose sublingual buprenorphine/naloxone followed by early administration of extended-release buprenorphine quickly and safely relieved withdrawal symptoms in 2 fentanyl users who presented to the hospital emergency department. This novel approach shows promise in improving treatment retention rates for patients using fentanyl. Further research is required to evaluate the safety and effectiveness of this approach.