This study investigates the use of tacrolimus extended release in stable patients who have undergone a heart transplant. All patients will receive the study medication free of charge for the 1 year duration of the study.

Tacrolimus has been extensively studied in solid organ transplantation. It is FDA approved for heart transplant recipients as a twice a day formulation (Prograf brand name, as well as generic formulations). A modified release formulation is available and FDA approved for kidney transplant recipients (Astagraf, Astellas Pharmaceutical), but is not approved for heart transplant patients.

In this study the investigators will study 100 patients who are stable on twice a day Tacrolimus and convert these subjects to once a day modified release Tacrolimus. The investigators will observe these patients for 1 year following the switch and assess safety and efficacy in a heart transplant population.

Inclusion Criteria:

• Adult, age 18 or higher
• Heart transplant recipient at least 365 days post-transplant at time of study screening
• Informed consent available
• Willingness to return for study visits, clinically indicated bloodwork
• On tacrolimus-based chronic immunosuppression.
• Self-identified ethnic group is provided

Exclusion Criteria:

• Prior heart or solid organ transplant
• Less than 365 days post-transplant at study screening
• Receiving cyclosporine based immunosuppression or calcineurin inhibitor free regimen
• Concurrent kidney or other solid organ
• Inability to provide informed consent
• More than 15 years post-transplant