Palbociclib and Clindamycin: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jul 1, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Palbociclib
Clindamycin
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. Palbociclib (Ibrance), your cancer medicine, can gently slow down a liver enzyme called CYP3A. Clindamycin, an antibiotic, is partly broken down by that same enzyme. So when you take both, a little more clindamycin may stay in your body than usual, which could mean a higher chance of side effects like stomach upset or diarrhea.
I want to be honest with you: this concern is mostly theoretical, based on how the drugs work rather than lots of real-world reports. The good news is your care team can manage it easily by keeping an eye on how you feel and adjusting things if needed. Keep taking both as prescribed and let them know about any new symptoms.
Mechanism: Palbociclib is a weak, time-dependent CYP3A inhibitor. Clindamycin is a CYP3A substrate, so co-administration may modestly increase clindamycin exposure (AUC/Cmax) and the risk of dose-related toxicity.
- Direction: increased substrate exposure (neither drug is a prodrug requiring CYP3A activation).
- Magnitude: palbociclib increased midazolam AUC/Cmax in interaction studies; effect on clindamycin extrapolated.
- Onset: unspecified.
- Evidence: theoretical.
- Management: monitor for clindamycin-related toxicity (GI effects, diarrhea/C. difficile risk); consider substrate dose reduction if clinically indicated, individualized by the care team.
What happens
Increased exposure to CYP3A substrates with a narrow therapeutic index
Interaction Deep Dive
When palbociclib, which acts as a weak, time-dependent inhibitor of CYP3A, is given together with a CYP3A substrate that has a narrow therapeutic index (NTI), the substrate's exposure and adverse effects may rise. In drug interaction studies, giving midazolam alongside repeated doses of palbociclib produced higher midazolam AUC and Cmax values. If these agents are combined, reducing the dose of the CYP3A substrate should be considered, and patients should be watched for signs of toxicity1.
Why it happens (mechanism)
Inhibition of CYP3A substrate metabolism by palbociclib
How to manage this interaction
The key message: this is manageable. Keep taking both palbociclib and clindamycin exactly as prescribed unless your care team tells you otherwise.
- Your team may monitor you more closely for clindamycin side effects, especially stomach upset and diarrhea.
- If needed, your clindamycin dose may be adjusted and individualized by your prescriber.
- Report new or worsening diarrhea, cramping, or other symptoms to your pharmacist or doctor promptly, since these can matter with antibiotics.
Ask your pharmacist to review your full medication list so nothing is missed.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) When midazolam (a CYP3A substrate) was given together with repeated doses of palbociclib 125 mg/day in healthy subjects (N=26), the AUC and Cmax of midazolam rose by 61% and 37%, respectively 1.
Common questions
Can I take Palbociclib and Clindamycin together?
Palbociclib may slightly raise clindamycin levels by slowing its breakdown, so watch for antibiotic side effects like diarrhea and let your care team know; they can adjust and monitor as needed. This concern is theoretical, not proven. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Palbociclib and Clindamycin 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 is the Palbociclib and Clindamycin interaction managed?
The key message: this is manageable. Keep taking both palbociclib and clindamycin exactly as prescribed unless your care team tells you otherwise. Your team may monitor you more closely for clindamycin side effects, especially stomach upset and diarrhea. If needed, your clindamycin dose may be adjusted and individualized by your prescriber. Report new or worsening diarrhea, cramping, or other symp… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Palbociclib or Clindamycin 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: IBRANCE(R) oral capsules, palbociclib oral capsules. Pfizer Labs (per FDA), New York, NY, 2019. DailyMed
Keep reading about Palbociclib
Keep reading about Clindamycin
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