Fifty-six patients with lumbar disc herniation were randomized to receive percutaneous endoscopic interlaminar discectomy (PEID) plus epidural dexamethasone (15 mg) + vitamin B12 (1 mg) (combined treatment; n=28) or PEID plus epidural saline (single surgery; n=28). The primary outcome was pain (VAS for low back and leg) at prespecified time points. Secondary outcomes included JOA, ODI, serum TNF-α/IL-6/PGE2, adverse events, postoperative length of stay, and modified MacNab criteria. Outcomes were assessed at postoperative days (POD) 1, 3, and 7, and at 1, 3, and 6 months. Overall, the results showed significantly lower early pain scores (POD 1–7) and better function (JOA/ODI) at POD 7 with the combined regimen, alongside lower inflammatory markers on POD 3 and a shorter hospital stay; longer-term outcomes at 6 months were similar between groups. These findings suggest that adding epidural dexamethasone plus B12 improves early recovery after PEID without changing 6-month global outcomes.