- Drug Administration: After randomization (to either twice daily tacrolimus or once daily Envarsus ®) and the "run-in" period, patients will be continued on their assigned tacrolimus formulation for 4 months. He/she will then be then switched to the opposite tacrolimus formulation. Following the switch, there will be a 14 day run-in period to establish the optimal trough level (5-8 ng/ml) (analogous to the first run-in period) and then continued on that tacrolimus formulation for 4 months.