Tacrolimus for Crohn's disease.

(1) Tacrolimus (FK-506) is an immunosuppressant that is being investigated for use in patients with Crohn's disease, mainly in those with refractory illness and fistulizing patterns of the disease. (2) Evidence from a small, randomized controlled trial indicates that, compared with placebo, tacrolimus is associated with higher rates of improvement and similar rates of remission in those with fistulizing patterns of disease. (3) Nephrotoxicity, which has been reported with the use of tacrolimus in clinical trials, seems to improve with dose reduction, but may be associated with irreversible histologic changes. (4) More studies are needed to determine the optimal dose and duration of therapy, and whether the drug is beneficial to patients with non-fistulizing patterns of Crohn's disease.