Rituximab and Belimumab Injection: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Belimumab Injection
Rituximab
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.
What happens
An increased risk of serious infections and post-injection systemic reactions
Interaction Deep Dive
Concomitant use of belimumab with rituximab may cause an increased incidence of serious infections and post-injection systemic reactions. Caution should be exercised if belimumab is administered in combination with rituximab1.
Why it happens (mechanism)
Unknown
Literature reports
1 report — tap to read
a) In a Phase III, randomized, double-blind, placebo controlled, 104-week study in adult patients with SLE, when compared with belimumab and placebo or belimumab plus standard therapy, belimumab in combination with rituximab was associated with higher frequency of serious adverse events (13.9%, 19.7%, 22.2%), serious infections (2.8%, 5.3%, 9%), and post-injection systemic reactions (9.7%, 5.3%, 13.2%) 1.
Common questions
Can I take Rituximab and Belimumab Injection together?
An increased risk of serious infections and post-injection systemic reactions Always confirm with your pharmacist or prescriber before making any change.
How serious is the Rituximab and Belimumab Injection interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Rituximab or Belimumab Injection 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)
- Product Information: BENLYSTA(R) intravenous, subcutaneous injection, belimumab intravenous, subcutaneous injection. GlaxoSmithKline (per FDA), Research Triangle Park, NC, 2023. DailyMed
Keep reading about Belimumab Injection
Keep reading about Rituximab
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.
Check another combination
Our instant two-drug interaction checker is almost here.
Still have questions about this combination?
Every question gets a real answer from a licensed pharmacist — free, and usually within a day.
Ask the pharmacist