Tacrolimus inhibits the complexion of calcineurin with its respective cytoplasmic receptors cyclophilin and FK-binding protein 12 (FKBP-12), both of which regulate a calmodulin dependent-phosphatase. Tacrolimus has been found to be efficacious in the treatment of patients with moderate to severe UC. Unfortunately, because of the safety profile with long term use, the drug is mostly used as an induction agent.