Cellcept vs Myfortic: Clinical Equivalence with Formulation-Specific Considerations
Both Cellcept (mycophenolate mofetil) and Myfortic (enteric-coated mycophenolate sodium) are bioequivalent and provide equivalent immunosuppressive efficacy, making either acceptable for organ transplant recipients and autoimmune disease patients, with the choice primarily driven by gastrointestinal tolerability. 1
Bioequivalence and Interchangeability
Cellcept and Myfortic deliver equivalent mycophenolic acid (MPA) exposure, with the 90% confidence interval for the ratio of EC-MPS to MMF for plasma AUC ranging from 101.1% to 114.5%, confirming bioequivalence across multiple studies in stable renal transplant recipients 1
Both formulations inhibit inosine monophosphate dehydrogenase (IMPDH), thereby suppressing T and B lymphocyte proliferation through the same mechanism of action 2
Conversion between formulations is safe and does not increase rejection risk, with studies showing only 3 acute rejections and no graft failures when converting stable transplant recipients from MMF to EC-MPS 3
Key Differentiating Factor: Gastrointestinal Tolerability
Myfortic was specifically developed to reduce gastrointestinal adverse effects through its enteric coating, which delays drug release until the small intestine 1, 4
Cellcept is associated with gastrointestinal adverse events (diarrhea, nausea, vomiting, abdominal cramps) in up to 35% of patients, which can lead to dose reduction or therapy withdrawal 2, 4
When converting from Cellcept to Myfortic, only 22% of patients experienced gastrointestinal adverse events, and only 10% required dose reduction for any adverse event 3
Critical Caveat on Gastrointestinal Effects
Myfortic can still cause colitis, though this is rare. A case report documented enteric-coated mycophenolate sodium-induced colitis in a heart transplant recipient, which resolved within 48 hours of discontinuation 5
The mechanisms underlying gastrointestinal disorders with both formulations are complex and relate to effects of both mycophenolic acid and its acyl glucuronide metabolite, as well as decreased immunity from general immunosuppression 4
Dosing Equivalence
720 mg Myfortic twice daily is equimolar to 1000 mg Cellcept twice daily 3
Both formulations are typically initiated immediately post-transplantation at standard doses (2-3 g/day for Cellcept) in combination with tacrolimus and corticosteroids 6
Patients can be safely converted from different doses of Cellcept to a standard dose of Myfortic without requiring exact equimolar conversion 3
Long-Term Management Considerations
Both formulations should be continued indefinitely in organ transplant recipients with stable graft function, as long-term immunosuppression is essential to prevent rejection and preserve graft survival 6
For autoimmune hepatitis patients who fail standard-of-care steroids and azathioprine, mycophenolate (either formulation) is conditionally recommended as initial second-line therapy with very low certainty of evidence 7
In systemic autoimmune rheumatic disease-associated interstitial lung disease, mycophenolate is conditionally recommended as a preferred first-line treatment option 7
Monitoring Requirements (Identical for Both Formulations)
Obtain CBC counts and renal/hepatic profiles every 1-3 months during therapy 7
Monitor for hematologic toxicity (leukopenia, anemia, thrombocytopenia), which may require temporary dose reduction or discontinuation 2
If gastrointestinal adverse effects develop with either formulation, interruption of therapy or dose reduction is recommended 7
Monitor for signs of progressive multifocal leukoencephalopathy and cease treatment if suspected 7
Clinical Decision Algorithm
Start with Myfortic if:
- Patient has history of gastrointestinal intolerance to immunosuppressants
- Patient has pre-existing gastrointestinal conditions
- Cost difference is not prohibitive
Use Cellcept if:
- Myfortic is not available or cost is prohibitive
- Patient is already stable on Cellcept with good tolerability
- Institutional protocols favor Cellcept
Convert from Cellcept to Myfortic if:
- Patient develops gastrointestinal adverse effects on Cellcept (diarrhea, nausea, vomiting, bloating) 3
- Dose reductions of Cellcept are being considered due to GI intolerance
- Patient requests conversion due to tolerability concerns
Common Pitfalls to Avoid
Never discontinue either formulation abruptly in patients with functioning grafts, as rejection risk persists indefinitely 6
Do not assume Myfortic eliminates all gastrointestinal risk—it reduces but does not eliminate GI adverse events 3, 5
Avoid premature withdrawal based solely on time post-transplant rather than clinical indicators 6
In failing allografts, withdraw the antimetabolite (either Cellcept or Myfortic) first while maintaining calcineurin inhibitor therapy to prevent donor-specific antibody formation 6