Direct Correlation Between Tacrolimus Levels and Serum Creatinine Seen Only Early After Transplant.

Abstract

Calcineurin inhibitors are a known cause of acute and chronic renal toxicity. It's unclear, however, whether tacrolimus trough levels correlate directly with serum creatinine levels, and if so, how long do those correlations persist. METHODS: We reviewed data on 19 liver transplant recipients (mean age, 51.8 yr; median, 50 yr) whose tacrolimus-based immunosuppression began between 1/2009 and 12/2011. We recorded trough tacrolimus levels and serum creatinine levels whenever the two markers were analyzed simultaneously; we also recorded the posttransplant interval at which the simultaneous levels were drawn. The data were non-parametrically distributed, so Spearman's rho was used for statistical analysis. RESULTS: During follow-up for a mean of 857 days (median 995 days), there were 731 simultaneous measurements of trough tacrolimus and creatinine. There were an average of 40 observations per patient (range 16-92). Overall, tacrolimus trough levels and serum creatinine were strongly correlated (R = 0.081, p=0.029). Upon closer analysis, however, the correlation was significant only for measurements obtained within 12 months of transplant (p<0.001). Beyond 12 months, there was no correlation. CONCLUSION: The correlation between tacrolimus trough levels and creatinine is only present early after transplant. After 12 months, renal impairment may be chronic and multifactorial and not as easily corrected by lowering the tacrolimus dose. Minimizing the tacrolimus dose early after transplant may be important in preventing chronic renal effects.