Background and Importance A combination of a calcineurin inhibitor with an antimetabolite and corticosteroids is the standard immunosuppression regime after liver transplant. Therapeutic drug monitoring (TDM) is recommended for tacrolimus due to its narrow therapeutic margin in order to avoid transplant rejection.

Aim and Objectives To report a case of a liver-transplant patient that required sublingual tacrolimus owing to intestinal malabsorption to reach therapeutic levels.

Material and Methods A 37-year-old woman with history of obesity and bariatric surgery (gastric bypass with union of ileum to stomach) was admitted to our centre in January 2023 with the diagnosis of fulminant liver failure and received an emergency transplant. Prolonged-release tacrolimus tablets 0.1 mg/kg/day (with subsequent adjustments according to blood trough concentrations), intravenous mycophenolate mofetil 1000 mg/12 hours, and intravenous methylprednisolone were initiated. During her evolution, she presented sustained sub-therapeutic tacrolimus concentrations (target trough concentrations for the first 4 weeks post-transplant when combined with mycophenolate and corticosteroids: 6–10 ng/mL) (figure 1A), as well as elevated levels of transaminases, which together with a biopsy confirmed a type II acute rejection and was re-transplanted in February 2023. Given the suspicion of tacrolimus malabsorption due to her history of bariatric surgery, alternatives were sought. A systematic review ¹ concluded that sublingual administration of immediate-release tacrolimus was an adequate strategy to reach therapeutic levels in lung and kidney transplant patients with a 1:2 sublingual: oral ratio. The Pharmacy Service proposed switching to immediate-release tacrolimus capsules and sublingual administration.

Results 3 mg/12 hours sublingual tacrolimus was started (previous prolonged-release tacrolimus dose: 12 mg/day) with subsequent adjustment according to TDM results. Capsules content was deposited under patient‘s tongue, avoiding swallowing for 15 minutes and drinking liquids for 30 minutes. Sustained therapeutic levels of tacrolimus were reached (figure 1B) and a progressive decrease in transaminases was observed until reaching normal range values.

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Abstract 4CPS-114 Figure 1

Conclusion and Relevance Sublingual administration of tacrolimus could be a feasible strategy to reach therapeutic levels in patients with intestinal malabsorption and avoid possible rejections.

References and/or Acknowledgements 1. Pennington CA, Park JM. Sublingual tacrolimus as an alternative to oral administration for solid organ transplant recipients. Am J Heal Pharm. 2015;72(4):277–84.

Conflict of Interest No conflict of interest.