2026 Eastern States Conference

Title: Pharmacokinetic evaluation of sublingual to enteral tacrolimus conversion in lung transplant recipients 
  
Authors: Sydney Nguyen, PharmD; Felicia Wang, PharmD, BCCCP; Amy Janowski, PharmD; Bridget Betts, PharmD, BCCCP; Gaspar Hacobian, PharmD, BCPS 
Brigham and Women’s Hospital, Boston, MA 
 
Learning Objective: Identify an appropriate conversion ratio when transitioning tacrolimus from sublingual to enteral route of administration 
  
Self-Assessment Question: True or false: Sublingual administration of tacrolimus results in absorption and serum concentrations comparable to those achieved with enteral administration. 
  
Background: The purpose of this study was to evaluate the clinical appropriateness of a 1:1 sublingual-to-enteral tacrolimus conversion ratio, with the goal of minimizing subtherapeutic serum levels to support adequate immunosuppression post-lung transplant. 
 
Methods: This was a single-center, prospective-retrospective enrollment cohort study conducted at a tertiary medical center. Adult inpatients were included if they underwent lung transplantation and were initiated on sublingual tacrolimus during the same admission from January 2025 to March 2026. Patients were excluded if they received intravenous tacrolimus or fewer than five doses of sublingual tacrolimus prior to enteral transition. Subjects were followed for 30 days or until hospital discharge, whichever occurred first. The primary outcome was the change in steady-state tacrolimus serum concentration after sublingual to enteral transition. Secondary outcomes included the calculated dose conversion ratio, incidence of subtherapeutic levels after transition, percentage of levels within therapeutic range (8-12 ng/mL), incidence of acute organ rejection, and mortality. Adverse effects, including nephrotoxicity and cardiometabolic complications, were evaluated. Descriptive and inferential statistics were used to analyze baseline characteristics and outcomes. 
  
Results: This study included 30 patients. The mean difference in steady-state tacrolimus serum concentrations following enteral transition was -0.56 ± 3.90 (p=0.44). The mean calculated conversion ratio was 2.22 ± 1.15. Following enteral transition, 10% of patients remained subtherapeutic for the duration of the follow-up period. The percentage of levels within therapeutic range was significantly greater during enteral administration compared with sublingual administration (43.8% vs. 20.7%, p<0.001). Cardiometabolic complications and nephrotoxicity were observed during the study period; however, no episodes of acute organ rejection or death were reported.  
 
Conclusion: The current 1:1 tacrolimus dose conversion ratio recommended by our institution guidelines is inconsistently used in practice. This study supports the use of a 1:2 sublingual-to-enteral ratio to achieve equivalent serum concentrations in lung-transplant recipients.