1. Clinical Overview
Mycophenolate mofetil (MMF) is an immunosuppressive prodrug of mycophenolic acid (MPA). It is a potent, selective, non-competitive, and reversible inhibitor of inosine monophosphate dehydrogenase (IMPDH), an enzyme crucial for the de novo pathway of guanosine nucleotide synthesis. This action selectively inhibits the proliferation of T and B lymphocytes, making it a cornerstone in preventing acute rejection in solid organ transplantation. In India, it is also widely used for autoimmune conditions like lupus nephritis.
| Onset | Duration | Bioavailability |
|---|---|---|
| Rapidly converted to active MPA; immunosuppressive effects begin within hours of administration. | Pharmacodynamic effects persist beyond the plasma half-life, requiring twice-daily dosing to maintain adequate immunosuppression. | Approximately 94% for oral administration (as MPA). Food reduces MPA Cmax by 40%. |
2. Mechanism of Action
MMF is a prodrug that is hydrolyzed to mycophenolic acid (MPA). MPA is a potent, selective, uncompetitive, and reversible inhibitor of inosine monophosphate dehydrogenase (IMPDH), specifically the type II isoform which is upregulated in activated lymphocytes. Inhibition of IMPDH blocks the conversion of inosine monophosphate (IMP) to xanthine monophosphate (XMP), a critical step in the de novo synthesis of guanosine nucleotides (GDP, GTP).
3. Indications & Uses
- Prophylaxis of acute organ rejection in patients receiving allogeneic renal, cardiac, or hepatic transplants (in combination with ciclosporin and corticosteroids).
- Treatment of Lupus Nephritis (as per ACR and KDIGO guidelines) in patients with active disease, usually in combination with corticosteroids.
4. Dosage & Administration
Adult Dosage: Renal Transplant: 1g (two 500mg tablets) orally twice daily (2g/day total). Cardiac Transplant: 1.5g orally twice daily (3g/day total). Hepatic Transplant: 1g IV or 1.5g orally twice daily. Lupus Nephritis: 1-1.5g orally twice daily (2-3g/day total), often initiated at a lower dose (500mg BD) and titrated up.
Administration: Administer on an empty stomach, 1 hour before or 2 hours after food to avoid reduced bioavailability. Tablets should be swallowed whole, not crushed, broken, or chewed. If a dose is missed, take it as soon as remembered unless it is nearly time for the next dose. Do not double the dose. For GI intolerance, may be administered with food after consulting physician, accepting reduced Cmax.
5. Side Effects
Common side effects may include:
- Diarrhea (31-36%)
- Nausea (23-26%)
- Vomiting (13-22%)
- Abdominal pain
- Headache
- Leukopenia (Neutropenia)
- Anemia
- Upper respiratory tract infection
- Insomnia
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Acyclovir, Valacyclovir, Ganciclovir, Valganciclovir | Competition for renal tubular secretion may increase plasma levels of both MPA (as MPAG) and the antiviral drug, potentiating mutual toxicity (myelosuppression, neurotoxicity). | Major |
| Antacids containing Magnesium/Aluminum, Cholestyramine, Sevelamer | Significantly decrease MPA absorption by binding, reducing bioavailability by up to 40%. | Major |
| Proton Pump Inhibitors (PPIs), H2 Blockers | May alter gastric pH and potentially reduce MPA solubility and absorption, though clinical significance is variable. | Moderate |
| Rifampicin/Rifampin | Potent UGT inducer; increases metabolism of MPA to MPAG, reducing MPA exposure (AUC) by up to 70%. May lead to subtherapeutic immunosuppression. | Major |
| Phenytoin, Phenobarbital | Enzyme inducers; may reduce MPA levels. | Moderate |
| Oral Contraceptives (Ethinyl Estradiol, Norethindrone) | MPA may decrease plasma levels of contraceptives via induction of glucuronidation, reducing efficacy. Additional non-hormonal contraception is mandatory. | Major |
| Azathioprine | Concurrent use is not recommended due to overlapping myelosuppressive effects without proven synergistic benefit. | Contraindicated |
| Live Vaccines (e.g., MMR, Varicella, Yellow Fever, OPV) | Risk of disseminated vaccine-induced infection. Avoid. | Major |
| Warfarin | MPA may displace warfarin from protein binding sites, potentially increasing INR. Monitor INR closely. | Moderate |
7. Patient Counselling
- DO take the medication exactly as prescribed, at the same times each day.
- DO take on an empty stomach (1 hr before or 2 hrs after food) unless otherwise directed by your doctor for GI issues.
- DO use two effective forms of contraception during and for 6 weeks after therapy. Inform your doctor immediately if you suspect pregnancy.
- DO maintain a medication diary and carry a patient alert card.
- DO NOT crush, chew, or break the tablets.
- DO NOT receive live vaccines without consulting your doctor.
- DO NOT start any new medication (including OTC, herbal, Ayurvedic) without doctor's approval.
8. Toxicology & Storage
Overdose: Expected to exaggerate known adverse effects: severe neutropenia, severe nausea, vomiting, diarrhea, abdominal pain, and increased susceptibility to infections. Bleeding may occur.
Storage: Store at room temperature (15-30°C). Protect from moisture. Keep in the original container, tightly closed. Keep out of reach of children. Do not use after the expiry date printed on the pack.