Determining the conversion ratios for oral versus sublingual administration of tacrolimus in solid organ transplant recipients.

Tacrolimus is utilized as maintenance immunosuppression in solid organ transplant (SOT). Current literature has reported conflicting conversion ratios when transitioning between oral and sublingual tacrolimus, and the exact conversion ratio has not been fully established in SOT. The purpose of this study was to determine the conversion ratios between oral and sublingual tacrolimus needed to achieve equivalent whole blood concentrations in heart, kidney, liver, and lung transplant recipients. A retrospective, single-center analysis was conducted at Mayo Clinic in Florida. One hundred and eighteen hospitalized SOT recipients who received oral and sublingual tacrolimus during the same inpatient admission from June 1, 2012, through June 1, 2017, were reviewed. The median conversion ratio of sublingual to oral tacrolimus was 1.34 (IQR: 1.03-1.93) in all SOT, 1.25 (IQR: 1.08-1.64) in heart transplant, 1.23 (IQR: 1.1-2.06) in kidney transplant, 1.64 (IQR: 1.27-2.29) in liver transplant, and 1.34 (IQR: 0.94-1.93) in lung transplant. A slightly higher dose of oral tacrolimus is needed in the majority of solid organ recipients in our population when converting between sublingual to oral tacrolimus administration.