Omeprazole and Mycophenolate Mofetil: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jul 2, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Omeprazole
Mycophenolate Mofetil
No brand names on record
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
Here's what's going on. Mycophenolate mofetil is an important medicine that calms your immune system, often after a transplant. Your body has to convert it into its active form (called MPA) in your stomach, and that step works best in an acidic stomach.
Omeprazole lowers stomach acid. When acid drops, less of the mycophenolate dissolves and gets absorbed, so your body ends up with less of the active drug. That could make it work less well, which matters a lot when it's protecting a transplant.
The good news: your care team can manage this by checking your MPA blood levels and adjusting your dose as needed. Don't stop either medicine on your own, just talk with your doctor or pharmacist.
Effect: Reduced exposure to mycophenolic acid (MPA), the active moiety of mycophenolate mofetil (a prodrug).
Mechanism: Omeprazole-induced gastric pH elevation reduces MPA solubility and dissolution, decreasing absorption. Reported reductions: Cmax ~30-70%, AUC ~25-35%. Onset rapid; evidence established.
- Monitor for reduced immunosuppressive efficacy (e.g., rejection risk in transplant patients).
- Obtain MPA plasma levels before and after initiating or discontinuing the PPI to keep levels stable.
- Mycophenolate mofetil dose may need to be increased and individualized to achieve equivalent immunosuppression.
- Enteric-coated mycophenolate sodium exposure is not affected by PPIs and may be an alternative option to discuss.
Use omeprazole with caution in transplant patients on mycophenolate mofetil.
What happens
Reduced mycophenolic acid exposure
Interaction Deep Dive
When proton pump inhibitors have been given as single doses to healthy volunteers and as multiple doses to transplant recipients taking mycophenolate mofetil, reports indicate a decline in exposure to the active metabolite, mycophenolic acid (MPA). Investigators have measured a reduction of roughly 30% to 70% in MPA Cmax alongside a 25% to 35% decrease in MPA AUC, an effect that may stem from lowered MPA solubility as gastric pH rises. To confirm that MPA concentrations stay steady, measuring MPA plasma levels both before and after starting or stopping concurrent medications may be warranted2. Should mycophenolate mofetil and a PPI have to be used together, an increase in the mycophenolate mofetil dose may be required to achieve equivalent immunosuppressive results 4. When concurrent PPI use is unavoidable, watch patients for changes in efficacy 2. Exercise caution with omeprazole in transplant patients who are receiving mycophenolate mofetil 1.
Why it happens (mechanism)
Incomplete dissolution and decreased absorption of mycophenolate mofetil when the gastric pH is increased
How to manage this interaction
Keep taking both medicines as prescribed unless your care team tells you otherwise. This interaction is well documented and manageable.
- Your team may check your MPA blood levels before and after starting or stopping the omeprazole to make sure they stay stable.
- Your mycophenolate mofetil dose may need to be adjusted and individualized to keep it working well.
- Your team may monitor you more closely for any signs the mycophenolate is less effective.
- Ask your prescriber whether an enteric-coated mycophenolate sodium form could be an option, since PPIs do not appear to affect its levels.
Raise any questions with your pharmacist or transplant team.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
5 reports — tap to read
a) In a crossover study, 12 healthy subjects received omeprazole 20 mg twice daily for 4 days along with a single 1000 mg dose of mycophenolate mofetil given roughly one hour after the final omeprazole dose, which produced a 52% decrease in the Cmax and a 23% decrease in the AUC of MPA 1.
b) Decreased exposure to mycophenolate mofetil (CellCept(R)), but not to enteric-coated mycophenolate sodium (Myfortic(R)), was observed in healthy subjects when given together with omeprazole in 2 randomized, crossover pharmacokinetic studies that used a 1-week washout period (N=12 each). Mycophenolic acid (MPA) concentrations were compared after a single oral dose of mycophenolate mofetil 1000 mg or enteric-coated mycophenolate sodium 720 mg given as monotherapy, or combined with omeprazole 20 mg twice daily (begun 4 days earlier). All drugs were given in the fasted state with 240 mL of water. The mean Cmax of MPA was 21.7 +/- 9.9 mg/L when mycophenolate mofetil was given alone, versus 10.5 +/- 3.6 mg/mL when given with omeprazole (p less than 0.01). The mean AUC (0 to 12 hours) of MPA was 33.3 +/- 11.5 mg x hr/L when mycophenolate mofetil was given alone, versus 25.8 +/- 6.4 mg x hr/L when given with omeprazole (p less than 0.05). By contrast, the mean Cmax and AUC of MPA after enteric-coated mycophenolate sodium were not altered whether it was given alone (21.6 +/-6.5 and 31.8 +/- 7.7 mg/L, respectively) or with omeprazole (23.7 +/- 8 and 33.2 +/-6.5 mg/L, respectively) 3.
c) In a prospective, case-controlled pharmacokinetic study, giving pantoprazole 40 mg together with mycophenolate mofetil (1000 mg twice daily) and tacrolimus (dose adjusted to achieve target trough levels of 5 to 14 nanograms/mL) led to lowered mycophenolic acid concentrations in 22 heart transplant recipients. Combining pantoprazole caused significant reductions in mycophenolic acid concentrations at 30 minutes (8.3 mg/L vs 18.3 mg/L (0.0259 mmol/L vs 0.0571 mmol/L)) and 1 hour (10 mg/L vs 15.8 mg/L (0.03 mmol/L vs 0.0493 mmol/L)), but not at 2 hours. Pantoprazole also significantly decreased mycophenolic acid AUC (51.2 mg x hr/L vs 68.7 mg x hr/L) and Cmax (12.2 mg/L vs 20.6 mg/L (0.038 mmol/L vs 0.0643 mmol/L)) and lengthened the time to reach Cmax (Tmax; 60 +/- 27.8 minutes vs 46.4 +/- 22.2 minutes) 4.
d) Giving pantoprazole together with mycophenolate mofetil significantly reduced the mean serum concentrations of the active metabolite, mycophenolate acid (MPA), at 30 and 60 minutes after the dose compared with subjects who did not receive pantoprazole. Concurrent use also significantly reduced Cmax and AUC and increased Tmax of MPA compared with subjects not receiving pantoprazole. Eligible subjects were taking mycophenolate mofetil 1 to 2 g/day for autoimmune diseases (23 also receiving pantoprazole 40 mg/day and 13 not receiving proton pump inhibitors (non-PPI)). Mean MPA plasma concentrations at 30 and 60 minutes postdose were significantly lower in the pantoprazole-treated subjects than in the non-PPI treated subjects (9.2 mg/L vs 30.3 mg/L (0.0287 mmol/L vs 0.0945 mmol/L) at 30 minutes and 11 mg/L vs 18.3 mg/L (0.034 mmol/L vs 0.0571 mmol/L) at 60 minutes). Cmax was significantly reduced in the pantoprazole-treated subjects compared with the non-PPI subjects (14.2 mg/L vs 35.4 mg/L (0.0443 mmol/L vs 0.1105 mmol/L)) and Tmax was significantly delayed (61.6 minutes vs 36.4 minutes, respectively). Between 90 minutes and 12 hours postdose, MPA plasma concentrations were not significantly different between the groups. In the pantoprazole group, 5 patients had increased disease activity compared with 1 patient in the non-PPI group 5.
e) In a randomized crossover study of stable renal transplant patients (N=20), no significant difference was found in mycophenolic acid exposure when mycophenolate mofetil or enteric-coated mycophenolate sodium were given with or without pantoprazole 6.
Common questions
Can I take Omeprazole and Mycophenolate Mofetil together?
Omeprazole can lower the amount of active mycophenolic acid your body absorbs, which may make mycophenolate mofetil less effective. Keep taking both as prescribed and let your transplant team adjust the dose and monitor your levels. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Omeprazole and Mycophenolate Mofetil interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.
How is the Omeprazole and Mycophenolate Mofetil interaction managed?
Keep taking both medicines as prescribed unless your care team tells you otherwise. This interaction is well documented and manageable. Your team may check your MPA blood levels before and after starting or stopping the omeprazole to make sure they stay stable. Your mycophenolate mofetil dose may need to be adjusted and individualized to keep it working well. Your team may monitor you more closely… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "established". Well documented — supported by controlled studies or strong clinical data.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Omeprazole or Mycophenolate Mofetil need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (6)
- Product Information: KONVOMEP(TM) powder for oral suspension, omeprazole sodium bicarbonate powder for oral suspension. Azurity Pharmaceuticals Inc (per manufacturer), Woburn, MA, 2022. DailyMed
- Product Information: CELLCEPT(R) oral capsules, oral tablets, oral suspension, intravenous injection, mycophenolate mofetil oral capsules, oral tablets, oral suspension, intravenous injection. Genentech USA Inc (per FDA), South San Francisco, CA, 2022. DailyMed
- Kees MG, Steinke T, Moritz S, et al: Omeprazole impairs the absorption of mycophenolate mofetil but not of enteric-coated mycophenolate sodium in healthy volunteers. J Clin Pharmacol 2012; 52(8):1265-1272. PubMed
- Kofler S, Shvets N, Bigdeli AK, et al: Proton pump inhibitors reduce mycophenolate exposure in heart transplant recipients - a prospective case-controlled study. Am J Transplant 2009; 9(7):1650-1656. PubMed
- Schaier M, Scholl C, Scharpf D, et al: Proton pump inhibitors interfere with the immunosuppressive potency of mycophenolate mofetil. Rheumatology (Oxford) 2010; 49(11):2061-2067. PubMed
- Rissling O, Glander P, Hambach P, et al: No relevant pharmacokinetic interaction between pantoprazole and mycophenolate in renal transplant patients: a randomized crossover study. Br J Clin Pharmacol 2015; 80(5):1086-1096. PubMed
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Keep reading about Mycophenolate Mofetil
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