Cyclophosphamide and Cyclosporine: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Cyclosporine
Cyclophosphamide
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.
What happens
Decreased serum cycloSPORINE concentration
Interaction Deep Dive
The use of cyclophosphamide as part of the conditioning regimen for hematopoietic stem cell transplant (HSCT) significantly reduced the cycloSPORINE serum concentration for up to two weeks following HSCT. The interaction may increase the incidence of acute graft versus host disease in the cyclophosphamide-treated group compared to the non-cyclophosphamide-treated group1.
Why it happens (mechanism)
Unknown
Literature reports
1 report — tap to read
a) A retrospective study including 103 hematopoietic stem cell transplant (HSCT) recipients analyzed the effects of several factors (including cyclophosphamide treatment) on the pharmacokinetics of cycloSPORINE. The mean of the median serum cyclosporin concentrations during the two weeks following HSCT were found to be statistically different between groups treated with cyclophosphamide (149.7 ng/mL) and without cyclophosphamide (217.3 ng/mL) conditioning (p < 0.0001). CycloSPORINE 3 mg/kg I.V. was administered for 10 hours from day 1 of transplant, and taken orally thereafter. Conditioning regimens that consisted of cyclophosphamide were dosed at 60 mg/kg once daily I.V. for 2 days, and were given in combination with total body irradiation. Graft versus host disease (greater than or equal to grade 2) developed in 33 (61.1%) patients in the cyclophosphamide treated groups and in 21 (42.9%) patients in the non-cyclophosphamide treated groups (p = 0.0633) 1.
Common questions
Can I take Cyclophosphamide and Cyclosporine together?
Decreased serum cycloSPORINE concentration Always confirm with your pharmacist or prescriber before making any change.
How serious is the Cyclophosphamide and Cyclosporine interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
Questions for your pharmacist
- Does my dose of Cyclophosphamide or Cyclosporine 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 (1)
- Nagamura F, Takahashi T, Takeuchi M, et al: Effect of cyclophosphamide on serum cyclosporine levels at the conditioning of hematopoietic stem cell transplantation. Bone Marrow Transplant 2003; 32:1051-1058. PubMed
Keep reading about Cyclosporine
Keep reading about Cyclophosphamide
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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