ObjectiveOral (PO) non-steroidal anti-inflammatory drugs (NSAIDs) are commonly used to treat phlebitis and thrombus extension post-endovenous ablation. Few studies have evaluated diclofenac topical gel for treating post-ablation phlebitis. This study assesses diclofenac 1 percent (%) topical gel as a first-line treatment for patients with moderate to severe phlebitis post-ablation. MethodsFrom December 2021 to March 2024, a retrospective cohort study was performed to identify patients who developed post-ablation phlebitis and were treated with either diclofenac topical gel (with or without PO NSAIDs) versus PO NSAIDs alone. All patients were evaluated with a numeric pain rating scale (NPRS, 0-10) at four-time intervals (1, 7, 14, and 30 days) after initiating treatment. ResultsOverall, 45 patients were included in the study, with 38 in the Diclofenac +/- PO NSAIDs group (9 males and 29 females) and 7 in the PO NSAIDs alone group (all females). NPRS scores showed similar pain reduction trends at all time intervals. Topical diclofenac gel was non-inferior to PO treatments and resulted in partial to complete relief in most patients at 30 days. At the 30 day follow up interview, 57% of patients preferred the diclofenac topical gel due to its ease of use and immediate local pain reduction. ConclusionsPatients with moderate to severe post-ablation phlebitis respond well to diclofenac topical gel with or without PO NSAIDs. Moreover, patients often had significant pain relief without additional need for PO NSAIDs. Longitudinal studies are needed to support the use of diclofenac topical gel for post-ablation phlebitis.