560 MMF has been approved for the prophylaxis of heart and renal transplants (Tx). An IV formulation that will enable MMF to be administered to patients unable to tolerate oral medication has just be released. Two related studies were performed to determined the safety, tolerability and pharmacokinetics (PK) of IV MMF in the immediate post-Tx period. The safety study was double-blind; the PK study was open label. Within 24 h after Tx, 153 (safety study) and 45 (PK study) first or second renal Tx recipients were started on IV MMF or placebo (used in the safety study only, 2:1 MMF:placebo). 1gm Q12h was administered over 2 hr via a dedicated peripheral venous catheter. In the safety study, oral MMF (1g Q12h) or placebo was administered starting within 72 hr post-Tx whereas in the PK study oral MMF was started on the evening of Day 5. Blood samples for PK analyses were obtained on study Days 5 (IV MMF) and 6 (PO MMF) immediately predose (at 0 minutes), at 20, 30, 40, 60, 80, 100, 120, 140, and 160 minutes, and at 3, 4, 6, 8, and 12 hours after the AM dose. Plasma samples were analyzed for MPA and mycophenolic acid glucuronide (MPAG) concentrations by HPLC. AUC was calculated using the linear trapezoidal rule. Adverse events (AEs) were monitored throughout treatment. Particular attention was paid to the peripheral IV infusion sites. The MPA AUC0-12 was higher for IV than PO MMF (40.8± 11.4 μg·h/mL vs. 32.9± 15, p<0.001). There were no other significant PK differences for plasma MPA or MPAG. In the safety study (n=98 IV MMF vs. n=55 placebo), 11 patients (11%) in the IV MMF and 4 patients (7%) in the placebo group discontinued during the entire study because of AEs. Overall, the AE experience did not differ between IV MMF and placebo. Injection site phlebitis (4%), and thrombosis (4%) were observed only in the IV MMF group. An equal percentage had injection site complaints that led to cessation in 1 patient (placebo group). In conclusion, IV MMF (1 gm, b.i.d.) administered over 2 hr in the immediate post-Tx period provides a somewhat higher MPA exposure than that obtained following PO medication. Based on the known PK/PD relationship for MPA-AUC, it is anticipated that a 1 gm IV dose of MMF administered b.i.d. will provide efficacy at least equivalent to oral capsules. IV MMF administered by peripheral infusion over 2 hr provides an acceptable alternative dose form in the immediate post-Tx period, however central venous infusion maybe preferred if a line is available. This Study was supported by Hoffmann-La Roche, Inc. Nutley, N.J and in part by PHS MO1RR750.