Elacestrant and Tenofovir Alafenamide: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Elacestrant
Tenofovir Alafenamide
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
Increased tenofovir alafenamide or tenofovir disoproxil fumarate exposure
Interaction Deep Dive
Concomitant use of tenofovir alafenamide or tenofovir disoproxil fumarate with a P-gp inhibitor that are also BCRP inhibitor may increase tenofovir alafenamide or tenofovir disoproxil fumarate exposure, which may increase the risk of tenofovir alafenamide or tenofovir disoproxil fumarate-associated adverse events123.
Why it happens (mechanism)
Inhibition of BCRP-mediated efflux transport of tenofovir alafenamide or tenofovir disoproxil fumarate ; inhibition of P-gp-mediated efflux transport of tenofovir
Literature reports
1 report — tap to read
a) A woman in her mid 60s with a previous diagnosis of HIV-1 and previous hepatitis B infection was admitted to the hospital with a 2-week history of nausea, vomiting, and diffuse myalgia. Her antiretroviral therapy (ART) regimen had recently been changed to tenofovir disoproxil fumarate (TDF)/emtricitabine (FTC) 300 mg/200 mg and darunavir (DRV)/cobicistat 800 mg/150 mg following discovery of genotypic resistance mutations and increasing HIV viral load on previous ART regimens. The patient's CrCl gradually decreased to 33.6 mL/min prior to admission, so TDF/FTC dosing was reduced to once every 2 days which resulted in tenofovir levels of 136 nanograms/mL at trough and 563 ng/mL 4 hours after dosing. Total bilirubin was 1.74 mg/dL, ALT was 84 U/L, AST was 77 U/L, lactate dehydrogenase was 404 U/L and creatine phosphokinase was 163 U/L. Her CrCl decreased after admission to less than 30 mL/min and TDF/FTC was discontinued. She developed dyspnea on the fifth day, and serum lactate was found increased to 15.3 mmol/L, confirming type B lactic acidosis. TDF/FTC and DRV/cobicistat were discontinued and the patient was treated with IV fluids with glucose and sodium bicarbonate. Liver function was improved 3 months after admission, but her HIV viral load increased to 3.4 x 10(5) copies/mL, and DRV/cobicistat and raltegravir were started. The authors proposed that tenofovir absorption was enhanced by inhibition of P-gp by cobicistat, resulting in elevated tenofovir levels 4.
Common questions
Can I take Elacestrant and Tenofovir Alafenamide together?
Increased tenofovir alafenamide or tenofovir disoproxil fumarate exposure Always confirm with your pharmacist or prescriber before making any change.
How serious is the Elacestrant and Tenofovir Alafenamide interaction?
It is rated moderate. Can be significant — usually manageable with 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 Elacestrant or Tenofovir Alafenamide 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 anything you'd monitor while I'm on both?
References (4)
- Product Information: DESCOVY(R) oral tablets, emtricitabine tenofovir alafenamide oral tablets. Gilead Sciences Inc (per FDA), Foster City, CA, 2025. DailyMed
- Product Information: BIKTARVY(R) oral tablets, bictegravir, emtricitabine, tenofovir alafenamide oral tablets. Gilead Sciences Inc (per FDA), Foster City, CA, 2024. DailyMed
- Product Information: VIREAD(R) oral tablets, oral powder, tenofovir disoproxil fumarate oral tablets, oral powder. Gilead Sciences, Inc (per FDA), Foster City, CA, 2019. DailyMed
- Isoda A, Mihara M, Matsumoto M, et al: Severe lactic acidosis during tenofovir disoproxil fumarate and cobicistat combination for HIV patient. BMJ Case Rep 2023; 16(11):e255751. PubMed
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