Effectiveness and long-term safety of thiazolidinediones and metformin in renal transplant recipients.

OBJECTIVE: To 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).
METHODS: Retrospective 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 A1c; 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.
RESULTS: Thirty-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 A1c from baseline was not significant in either study group. Development of congestive heart failure or liver function abnormalities was not observed.
CONCLUSIONS: Metformin 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.