Impact of concurrent gabapentin or pregabalin with high-dose melphalan in patients with multiple myeloma undergoing autologous hematopoietic stem cell transplant

Background Melphalan is an alkylating agent used in both autologous (ASCT) and allogeneic stem cell transplantation. It is a substrate of L-type amino acid transporter-1 (LAT-1) and LAT-2, which are involved in its tissue penetration and elimination. Gabapentin and pregabalin, common concomitant medications in patients with multiple myeloma undergoing ASCT, are also substrates of LAT transporters, raising concern for potential competitive inhibition of melphalan transport. We evaluated whether concurrent use of gabapentin or pregabalin in patients receiving high-dose melphalan (>= 140 mg/m(2)) prior to ASCT impacted frequency and severity of melphalan-related adverse events. Objective We aimed to determine if concurrent administration of gabapentin or pregabalin and melphalan increased melphalan toxicity. Methods This was a single-center, retrospective evaluation including patients >= 18 years of age who received high-dose melphalan as part of a conditioning regimen at the Winship Cancer Institute of Emory University between August 1, 2010 and April 1, 2020 and were followed through their transplant admission. After identification and inclusion of patients who received melphalan in combination with gabapentin or pregabalin, patient matching based on age (+/- 5 years), sex, and melphalan dose (140 mg/m(2) or 200 mg/m(2)) was utilized to generate a comparable cohort of patients who received melphalan alone. The primary outcome was hospital length of stay (LOS); secondary outcomes included supportive care requirements between days +4 and day +14 and time to neutrophil and platelet-20 engraftment. Results Among 176 patients evaluated in each group, median hospital LOS was 16 days, median time to neutrophil engraftment was 14 days, and median time to platelet-20 engraftment was 16 days in both groups. In addition, there were no significant differences in supportive care requirements between groups. Conclusion In this study, use of gabapentin or pregabalin in combination with melphalan did not impact safety of the conditioning regimen in patients undergoing ASCT.