Background Tacrolimus is an immunosuppressive agent with a narrow therapeutic range (5–15 ng/ml for solid organ transplants). Achieving and maintaining appropriate tacrolimus exposure are critical for preventing rejection and minimising toxicity.

Although tacrolimus can be delivered either orally or intravenously, oral tacrolimus is associated with fewer adverse effects. It has been suggested that the sublingual route may be used as an alternative to oral in critical care patients when the enteric route is not available.

Purpose The aim of this study was to compare tacrolimus drug exposure after sublingual or enteric administration in solid organ transplanted critical care patients.

Material and methods A retrospective observational study was carried out of the adults in an intensive care unit of a tertiary hospital from June to December 2017.

All oral immediate release tacrolimus prescriptions were reviewed during this period. Patient records were reviewed and the following data was collected: patient number, administered drug, total daily dose, route, start day and last day of the administration.

Prescription data was linked to tacrolimus levels laboratory results for each patient and of treatment. Tacrolimus levels corresponding to each route were analysed, and mean and standard deviation was performed. Tacrolimus blood concentration levels considered toxic (>20 ng/ml) were identified.

Results Seventy-eight patients were treated with oral immediate release tacrolimus during the period of study: 1201 tacrolimus drug concentration level analysis were performed (mean of all drug blood concentrations: 11.12 ng/ml, standard deviation (SD):±5,59 ng/ml).

Oral (by mouth) administration drug concentrations levels (n=209) mean was 9.68 ng/ml (SD=±4.39 ng/ml). Two drug results (0.96%) were reported to be >20 ng/ml.

Nasogastric tube administration drug concentration levels (n=572) mean was 11.11 ng/ml. (SD) ±6.29 ng/ml. 45 (7.87%) drug results were reported to be >20 ng/ml.

Sublingual administration drug concentration levels (n=420) mean was 11.85 ng/ml (SD=4.93 ng/ml). 30 (7.1%) drug results were reported to be >20 ng/ml.

Conclusion Tacrolimus drug exposure after sublingual administration is similar to enteric administration in this study. Sublingual administration of tacrolimus is as effective and safe as nasogastric tube administration when oral administration is not feasible, although the lack of an appropriate drug formulation.

Reference and/or acknowledgements Aliment Pharmacol Ther 2017;45:1225–31.

No conflict of interest.