Impact of Very Low-Dose Trimethoprim-Sulfamethoxazole on Serum Creatinine after Renal Transplantation: A Retrospective Study.

Background: It is well known that high-dose trimethoprim, through its effect of inhibiting creatinine secretion, increases serum creatinine levels without changes in real glomerular filtration rate. However, there has been no report regarding the effect of very low-dose trimethoprim on serum creatinine levels after renal transplantation.
Methods: We retrospectively investigated 76 renal transplantation recipient outpatients who completed their course of initial prophylaxis at our institution. Twelve patients who experienced events that might affect their serum creatinine levels were excluded. Fifty-one patients who required readministration of trimethoprim-sulfamethoxazole to prevent a possible outbreak of pneumocystis jirovecii pneumonia and 13 patients who did not receive readministration (control) were analyzed. Dosage was 80 mg/400 mg (per tablet), administered as 3 tablets per week for 30.6 ± 13.5 days. This study strictly complied with the Helsinki Congress and the Istanbul. Declaration regarding donor source.
Results: All patients completed readministration without adverse events. Serum creatinine increased significantly in the readministration group (1.40 ± 0.64 mg/dL to 1.48 ± 0.70 mg/dL, P < .01) while not in the control group. The higher the initial serum creatinine level, the greater the increase of Δ serum creatinine (R = 0.59, P < .001). Sex, baseline urine protein level, angiotensin-converting enzyme inhibitor/angiotensin receptor blocker use, donor type, and time after renal transplantation did not affect Δ serum creatinine. Serum creatinine returned to baseline levels after cessation.
Conclusions: Very low-dose trimethoprim-sulfamethoxazole prophylaxis significantly raised serum creatinine reversibly by 6% after renal transplantation.
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