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Does Tamoxifen Citrate Interact with Letrozole?

Tamoxifen Citrate and Letrozole have a contraindicated drug interaction according to U.S. FDA drug labeling data. Concomitant use not recommended. Tamoxifen reduced letrozole plasma concentration by 38%, and efficacy of combination in adjuvant treatment not established. The mechanism involves reduced letrozole plasma concentration by 38%. Patients taking both medications should consult their healthcare provider before starting, stopping, or changing the dosage of either drug. This information is based on official FDA drug labeling sourced from OpenFDA and the NIH National Library of Medicine.

Severity
Contraindicated
Letrozole Class
Aromatase Inhibitor
Management
Do not take together
Data Source
U.S. FDA via OpenFDA

How This Interaction Works

The interaction between Tamoxifen Citrate and Letrozole occurs because reduced letrozole plasma concentration by 38%. Clinically, this means concomitant use not recommended. tamoxifen reduced letrozole plasma concentration by 38%, and efficacy of combination in adjuvant treatment not established. Because of the severity of this interaction, these medications are contraindicated — meaning they should not be taken together under any circumstances. If you are currently taking both, contact your healthcare provider immediately to discuss alternatives.

What To Tell Your Doctor or Pharmacist

If you are taking Tamoxifen Citrate and your doctor is considering prescribing Letrozole (or vice versa), make sure to:

  • Inform your doctor and pharmacist of all current medications, including over-the-counter drugs and supplements
  • Ask whether the benefits of combining these medications outweigh the risks for your specific situation
  • Ask what symptoms to watch for that would indicate the interaction is causing problems
  • Ask about alternative medications that do not interact with your current regimen
  • Ask how frequently you should be monitored while these are co-prescribed
  • Never stop or change either medication without first consulting your healthcare provider
💊 Tamoxifen Citrate(Tamoxifen Citrate)+💊 Letrozole(Letrozole)

Severity & Interaction Details

⛔
contraindicated
Avoid this combination
FDA labeling lists this pair as contraindicated. The risk outweighs the benefit in nearly all cases.
Severity scale
MinorContra
On record
Yes
Drug A class
—
Drug B class
Aromatase Inhibitor
Source
NLP:tamoxifen citrate

What this means in plain English

Concomitant use not recommended. Tamoxifen reduced letrozole plasma concentration by 38%, and efficacy of combination in adjuvant treatment not established.

What the FDA label says

"Reduced letrozole plasma concentration by 38%"

📖 Source: NLP:tamoxifen citrate

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Data sourced from U.S. FDA drug labeling via openFDA and the NIH National Library of Medicine. For informational purposes only. Always consult your pharmacist or physician.