Mycophenolic Acid

How Does Mycophenolic Acid Work?

Mycophenolic acid works by reversibly inhibiting the enzyme inosine monophosphate dehydrogenase (IMPDH), the rate-limiting enzyme in the de novo synthesis of guanosine nucleotides (purines). By blocking this pathway, MPA depletes the supply of DNA building blocks that T and B lymphocytes need to proliferate and mount an immune attack on the transplanted organ.

The selectivity of mycophenolic acid for lymphocytes is what makes it particularly valuable: T and B cells rely heavily on de novo purine synthesis when activated, whereas most other cell types can compensate via an alternative salvage pathway. Additionally, MPA is fivefold more potent against the Type II isoform of IMPDH expressed in activated lymphocytes versus the Type I isoform expressed in most other cells. This selective cytostatic effect suppresses cell-mediated immune responses and antibody formation while sparing most other tissues.

Because IMPDH inhibition is reversible, twice-daily dosing is necessary to maintain continuous lymphocyte suppression. Skipping doses allows IMPDH activity to recover, creating windows of reduced immunosuppression that can trigger rejection in transplant recipients. Mycophenolate mofetil (CellCept) is a prodrug that is rapidly hydrolyzed to MPA in the body; mycophenolate sodium (Myfortic) delivers the sodium salt of MPA directly via an enteric-coated formulation that delays absorption until the intestine.

How Hard Is It to Find Mycophenolic Acid in Stock?

Generic mycophenolate mofetil (CellCept generic) is generally widely available in 2026 with no active FDA-declared nationwide shortage. Multiple manufacturers produce this formulation, providing supply redundancy. However, mycophenolate sodium delayed-release tablets (Myfortic generic) have a more limited manufacturer base and have experienced intermittent ASHP-tracked shortages from certain producers in past years. Individual pharmacies may occasionally run out of stock regardless of the national availability picture.

Because mycophenolate is classified as a specialty medication, not all retail pharmacies stock it in sufficient quantities. Specialty pharmacies that serve transplant patient populations typically maintain more consistent supply. If your pharmacy is out of stock, medfinder calls pharmacies near you to identify which ones have your specific formulation and strength in stock, then texts you the results—eliminating the need to call pharmacy after pharmacy yourself.

Who Can Prescribe Mycophenolic Acid?

The FDA prescribing information states that mycophenolate must be prescribed only by physicians experienced in immunosuppressive therapy and management of organ transplant patients. Mycophenolic acid is not a controlled substance, so no special DEA registration is required. However, the FDA REMS program for mycophenolate requires specific counseling and pregnancy testing for patients of reproductive potential.

Prescribers who commonly manage mycophenolic acid therapy include:

Transplant Surgeons — initiate immunosuppression regimens post-transplant

Transplant Nephrologists — manage long-term immunosuppression for kidney transplant recipients

Transplant Hepatologists — manage liver transplant recipients

Transplant Cardiologists — manage heart transplant recipients

Rheumatologists — prescribe for off-label autoimmune uses (lupus nephritis, vasculitis, etc.)

Dermatologists — prescribe for autoimmune skin conditions (pemphigus vulgaris, bullous pemphigoid)

Nurse Practitioners (NPs) and Physician Assistants (PAs) — may prescribe within transplant or specialty programs under physician oversight per state law

Telehealth options are increasingly available for stable, established transplant patients for follow-up appointments. Transplant centers that participated in telehealth expansion during COVID-19 may offer virtual visits for routine monitoring. For new patients or those requiring initial evaluation, in-person visits remain the standard of care.

Is Mycophenolic Acid a Controlled Substance?

No. Mycophenolic acid (Myfortic), mycophenolate mofetil (CellCept), and mycophenolate sodium are not classified as controlled substances under the DEA Controlled Substances Act. There are no special DEA prescriber registration requirements, no mandatory Prescription Drug Monitoring Program (PDMP) reporting, and no limits on days' supply imposed by controlled substance regulations.

However, mycophenolate products are subject to an FDA Risk Evaluation and Mitigation Strategy (REMS) due to the risk of embryofetal toxicity. The REMS requires prescribers to counsel patients of reproductive potential about pregnancy prevention, conduct pregnancy testing before and during therapy, and advise on the use of two forms of contraception during treatment and for at least 6 weeks after stopping. The Mycophenolate Pregnancy Registry (1-800-617-8191) is available for patients who become pregnant during therapy. Additionally, the FDA prescribing information states that mycophenolate must be prescribed only by physicians experienced in immunosuppressive therapy and management of organ transplant patients.

Common Side Effects of Mycophenolic Acid

The most common side effects are gastrointestinal and include:

Diarrhea, nausea, vomiting, stomach pain

Constipation and gas

Headache, tremor, dizziness, insomnia

Infections (UTIs, herpes/shingles, upper respiratory)

Anemia and leukopenia (low blood cell counts)

High blood pressure, swelling of ankles/feet

Serious Side Effects (Seek Medical Attention)

Progressive Multifocal Leukoencephalopathy (PML): Rare but life-threatening brain infection; symptoms include speech, vision, or muscle movement problems

Lymphoma and skin cancer: Increased risk due to immunosuppression (FDA boxed warning)

Serious infections: Including CMV, BK virus nephropathy, fungal, and opportunistic infections

Embryofetal toxicity: Significantly increased risk of miscarriage and birth defects (FDA boxed warning)

GI perforation/hemorrhage: Rare but serious; seek emergency care for severe abdominal pain, black stools, or coffee-ground vomit

Pure red cell aplasia: Rare bone marrow condition causing severe anemia

Final Thoughts on Mycophenolic Acid

Mycophenolic acid—whether taken as Myfortic (mycophenolate sodium) or as the closely related mycophenolate mofetil (CellCept)—is one of the most important medications in transplant medicine. For millions of transplant recipients worldwide, it is a lifelong daily medication that stands between their immune system and their transplanted organ. Understanding how it works, what interactions to avoid, and how to manage its side effects can help patients stay safe and adherent for the long term.

Cost is manageable: with GoodRx or discount cards, generic mycophenolate mofetil can be obtained for as little as $18–$28 per month, and mycophenolate sodium for $40–$42 per month. Patient assistance programs, Medicare Part B coverage for eligible kidney transplant patients, and 340B pricing at qualifying transplant centers provide additional savings avenues for those who need them.

If you ever have difficulty finding your medication in stock, medfinder can help you quickly locate which pharmacies near you have your specific formulation and strength in stock, so you never have to risk missing a dose.