Mycophenolate Mofetil 250 mg · Tablets

Mycophenolate mofetil (MMF) is absorbed following oral administration and hydrolyzed to mycophenolic acid (MPA), the active metabolite. MPA is a selective uncompetitive inhibitor of the two isoforms (type I and type II) of inosine monophosphate dehydrogenase (IMPDH) leading to inhibition of the de novo pathway of guanosine nucleotide synthesis and blocks DNA synthesis. The mechanism of action of MPA is multifaceted and includes effects on cellular checkpoints responsible for metabolic programming of lymphocytes. MPA shifts transcriptional activities in lymphocytes from a proliferative state to catabolic processes. In vitro studies suggest that MPA modulates transcriptional activities in human CD4+ T-lymphocytes by suppressing the Akt/mTOR and STAT5 pathways that are relevant to metabolism and survival, leading to an anergic state of T-cells whereby the cells become less responsive to antigenic stimulation. Additionally, MPA enhanced the expression of negative co-stimulators such as CD70, PD-1, CTLA-4, and transcription factor FoxP3 as well as decreased the expression of positive co-stimulators CD27 and CD28.

MPA decreases proliferative responses of T- and B-lymphocytes to both mitogenic and allo-antigenic stimulation, antibody responses, as well as the production of cytokines from lymphocytes and monocytes such as GM-CSF, IFN-Ɣ, IL-17, and TNF-α. Additionally, MPA prevents the glycosylation of lymphocyte and monocyte glycoproteins that are involved in intercellular adhesion to endothelial cells and may inhibit recruitment of leukocytes into sites of inflammation and graft rejection.

Overall, the effect of MPA is cytostatic and reversible.

Absorption — Following oral and intravenous administration, MMF undergoes complete conversion to MPA, the active metabolite. In 12 healthy volunteers, the mean absolute bioavailability of oral MMF relative to intravenous MMF was 94%. Two 500 mg mycophenolate mofetil tablets have been shown to be bioequivalent to four 250 mg mycophenolate mofetil capsules. Five mL of the 200 mg/mL constituted mycophenolate mofetil oral suspension have been shown to be bioequivalent to four 250 mg capsules.

The mean (±SD) pharmacokinetic parameters estimates for MPA following the administration of MMF given as single doses to healthy volunteers, and multiple doses to kidney, heart, and liver transplant patients, are shown in Table 10. The area under the plasma-concentration time curve (AUC) for MPA appears to increase in a dose-proportional fashion in kidney transplant patients receiving multiple oral doses of MMF up to a daily dose of 3 g (1.5g twice daily) (see Table 10).

In the early post-transplant period (less than 40 days post-transplant), kidney, heart, and liver transplant patients had mean MPA AUCs approximately 20% to 41% lower and mean Cmax approximately 32% to 44% lower compared to the late transplant period (i.e., 3 to 6 months post-transplant) (non-stationarity in MPA pharmacokinetics).

Mean MPA AUC values following administration of 1 g twice daily intravenous mycophenolate mofetil over 2 hours to kidney transplant patients for 5 days were about 24% higher than those observed after oral administration of a similar dose in the immediate post-transplant phase.

In liver transplant patients, administration of 1 g twice daily intravenous mycophenolate mofetil followed by 1.5 g twice daily oral mycophenolate mofetil resulted in mean MPA AUC estimates similar to those found in kidney transplant patients administered 1 g mycophenolate mofetil twice daily.

Effect of Food — Food (27 g fat, 650 calories) had no effect on the extent of absorption (MPA AUC) of MMF when administered at doses of 1.5 g twice daily to kidney transplant patients. However, MPA Cmax was decreased by 40% in the presence of food [see Dosage and Administration (2.1)].

Distribution — The mean (±SD) apparent volume of distribution of MPA in 12 healthy volunteers was approximately 3.6 (±1.5) L/kg. At clinically relevant concentrations, MPA is 97% bound to plasma albumin. The phenolic glucuronide metabolite of MPA (MPAG) is 82% bound to plasma albumin at MPAG concentration ranges that are normally seen in stable kidney transplant patients; however, at higher MPAG concentrations (observed in patients with kidney impairment or delayed kidney graft function), the binding of MPA may be reduced as a result of competition between MPAG and MPA for protein binding. Mean blood to plasma ratio of radioactivity concentrations was approximately 0.6 indicating that MPA and MPAG do not extensively distribute into the cellular fractions of blood.

In vitro studies to evaluate the effect of other agents on the binding of MPA to human serum albumin (HSA) or plasma proteins showed that salicylate (at 25 mg/dL with human serum albumin) and MPAG (at ≥ 460 mcg/mL with plasma proteins) increased the free fraction of MPA. MPA at concentrations as high as 100 mcg/mL had little effect on the binding of warfarin, digoxin or propranolol, but decreased the binding of theophylline from 53% to 45% and phenytoin from 90% to 87%.

Elimination — Mean (±SD) apparent half-life and plasma clearance of MPA are 17.9 (±6.5) hours and 193 (±48) mL/min following oral administration, respectively.

Metabolism — The parent drug, MMF, can be measured systemically during the intravenous infusion; however, approximately 5 minutes after the infusion is stopped or after oral administration, MMF concentrations are below the limit of quantitation (0.4 mcg/mL).