The purpose of this study is to determine if local intra-operative application of ZYNRELEF (topical medication) during shoulder replacement surgery improves pain control (as defined by opioid consumption after surgery) compared to the use of an interscalene block with catheter. This is a randomized clinical trial without blinding. Subjects will complete patient reported outcomes before and after surgery. Subjects will track their narcotic use, pain scores and pain satisfaction after surgery.

Inclusion Criteria:

1. Adult patients 18 years or older
2. Indicated to undergo primary total shoulder arthroplasty (anatomic or reverse)

Exclusion Criteria:

1. Any persons unable to consent, will not be eligible
2. Patients undergoing revision arthroplasty or reverse shoulder arthroplasty
3. Proximal humerus fractures
4. Inability to have interscalene anesthetic catheter placement
5. Compromised baseline renal function (CrCl < 50)
6. BMI > 40
7. History of GI bleed, prior duodenal surgery, or gastric sleeve resection
8. Current narcotic use or prior consistent narcotic exposure in the last 6 months
9. Use of perioperative oral steroid medications
10. Active Workman's compensation claim
11. Prior shoulder arthroplasty on the contralateral side in which an interscalene catheter was used