LAUSR

BACKGROUND Although effective for curtailing alloimmune responses, calcineurin inhibitors (CNIs) have an adverse-effect profile that includes nephrotoxicity. In lung transplant (LTx) recipients, the optimal serum levels of the CNI tacrolimus necessary to control alloimmune responses and minimize nephrotoxicity are unknown. METHODS This retrospective, single-center study reviewed tacrolimus whole blood trough levels (BTLs), grades of acute cellular rejection (ACR), acute rejection scores, and creatinine clearance (CrCl) obtained in LTx recipients within the first year after their transplant procedure. Comparisons were made between the first 90 days post LTx (when tacrolimus BTLs were maintained >10 µg/L) and the remainder of the post-LTX year (when BTLs were <10 µg/L). RESULTS Despite tacrolimus mean BTLs being higher during the first 90 days post LTx compared with the remainder of the first post-LTx year (10.4 ± 0.3 µg/L vs 9.5 ± 0.3 µg/L, P < .0001) there was no association with lower grades of ACR (P = .24). The intensity of ACR (as determined by acute rejection scores) did not correlate with tacrolimus mean BTLs at any time during the first posttransplant year (P = .79). During the first 90 days post LTx there was a significant decline in CrCl and a correlation between increasing tacrolimus mean BTLs and declining CrCl (r = -0.26, P = .03); a correlation that was not observed during the remainder of the year (r = -0.09, P = .52). CONCLUSIONS In LTx recipients, maintaining BTLs of the CNI tacrolimus >10µg/L did not result in superior control of acute rejection responses but was associated with declining renal function.