Fulvestrant and Fluoroestradiol F 18: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Fulvestrant
Fluoroestradiol F 18
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
Reduced detection of estrogen receptor (ER)-positive lesions
Interaction Deep Dive
Certain systemic endocrine therapies that block estrogen receptors (ER), including ER modulators and ER down-regulators, reduce the uptake of fluoroestradiol F 18 and may reduce detection of ER-positive lesions. Before administering fluoroestradiol F 18, discontinue drugs that bind to the ER, such as fulvestrant for at least 28 weeks1.
Why it happens (mechanism)
Competition for binding the estrogen receptor
Common questions
Can I take Fulvestrant and Fluoroestradiol F 18 together?
Reduced detection of estrogen receptor (ER)-positive lesions Always confirm with your pharmacist or prescriber before making any change.
How serious is the Fulvestrant and Fluoroestradiol F 18 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 Fulvestrant or Fluoroestradiol F 18 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: CERIANNA(TM) intravenous injection, fluoroestradiol F18 intravenous injection. GE HealthCare (per FDA), Marlborough, MA, 2024. DailyMed
Keep reading about Fulvestrant
Keep reading about Fluoroestradiol F 18
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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