Tacrolimus-Induced Hyponatremia in Lung Transplant Recipients: A Case Series

BACKGROUND: Lung transplant recipients are treated with a 3-drug immunosuppressive regimen that consists of a calcineurin inhibitor, an antiproliferative agent, and a corticosteroid. Calcineurin inhibitors are the backbone of this regimen, and tacrolimus is used more often than cyclosporine, because tacrolimus is the more potent of the two agents. Tacrolimus-induced hyponatremia has been described among kidney transplant recipients, but not among lung transplant recipients. METHODS: We conducted a retrospective chart review of patients who underwent lung transplant at our institution and went on to develop severe hyponatremia. RESULTS: We identified 5 lung transplant recipients who developed severe hyponatremia after lung transplantation (median nadir, 117 mEq/L; interquartile range, 116-119 mEq/L). Time to development of hyponatremia ranged from 3 to 85 days posttransplant. Hyponatremia persisted in these patients despite fluid restriction, salt tablets, diuretics, and fludrocortisone therapy. Hyponatremia resolved in 3 patients and significantly improved in 2 patients after they were switched from a tacrolimus-based immunosuppressive regimen to a cyclosporine-based regimen. CONCLUSION: Transitioning from a tacrolimus- to a cyclosporine-based immunosuppressive regimen may resolve or improve severe hyponatremia in lung transplant recipients.