Effectiveness and Long-Term Safety of Thiazolidinediones and Metformin in Renal Transplant Recipients

ObjectiveTo investigate the long-term safety and effectiveness of thiazolidinediones and metformin in renal transplant recipients with posttransplant diabetes mellitus (PTDM) or preexisting diabetes mellitus (DM).MethodsRetrospective chart review was performed for renal transplant recipients with PTDM or preexisting DM followed up during the years 2000-2006. Data collected included baseline characteristics; glomerular filtration rate (GFR); creatinine; hemoglobin A_1c; and development of congestive heart failure, edema, and liver function abnormalities. GFR was calculated using the Modification of Diet in Renal Disease study equation calculator.ResultsThirty-two patients comprised the metformin group (PTDM = 21, preexisting DM = 11), and 46 patients were included in the TZD group (PTDM = 33, preexisting DM = 13). Only 24 patients taking metformin and 31 patients taking TZDs were included for effectiveness analysis since the others required additional medications to control their DM. Mean follow-up was 16.4 months (range, 1-55 months) for patients treated with metformin and 37.1 months (range, 6-72 months) for patients treated with TZDs. GFR was decreased from baseline in all patients, but the only significant change was in patients with preexisting DM. While there was a significant change in creatinine levels in the metformin group, only 5 patients had to discontinue the drug because of this elevation (3 in preexisting DM group, 2 in PTDM group). Change in hemoglobin A_1c from baseline was not significant in either study group. Development of congestive heart failure or liver function abnormalities was not observed.ConclusionsMetformin appears to be safe in the renal transplant population for a mean duration of 16 months, although caution should be exercised using close monitoring in patients with preexisting DM. TZDs appear to be safe for a mean duration of 37 months after renal transplant. (Endocr Pract. 2008;14:979-984)