Tamoxifen has 19 known drug interactions based on U.S. FDA drug labeling data. Of these, 2 are contraindicated combinations that should be avoided entirely. 7 are classified as major interactions requiring close medical supervision. Notable interactions include combinations with Anastrozole, Anastrozole Tablets, Chloroquine Phosphate. Patients taking Tamoxifen should inform their healthcare provider of all current medications — including over-the-counter drugs and supplements — to avoid potentially harmful combinations. Data sourced from OpenFDA and the NIH National Library of Medicine.
- Total
- 19
- Contraindicated
- 2
- Major
- 7
- Moderate
- 9
- Minor
- 1
Contraindicated (2)
- Tamoxifen + Anastrozole— Do not use in combination with anastrozole. Co-administration reduced anastrozole plasma concentration by 27% and showed…
- Tamoxifen + Anastrozole Tablets— Do not use in combination with anastrozole tablets. Co-administration reduced anastrozole plasma concentration by 27% an…
Major (7)
- Tamoxifen + Chloroquine Phosphate— Concomitant use of chloroquine with tamoxifen is not recommended due to risk of retinal toxicity.
- Tamoxifen + Cyclophosphamide— Concomitant use may increase the risk of thromboembolic complications when used with cyclophosphamide-containing chemoth…
- Tamoxifen + Cyclophosphamide For Injection— Concomitant use with cyclophosphamide-containing chemotherapy may increase risk of thromboembolic complications.
- Tamoxifen + Fluoroestradiol F 18— Binds to estrogen receptor and competes with fluoroestradiol F 18, reducing detection of ER-positive lesions. Discontinu…
- Tamoxifen + Paroxetine— Paroxetine's CYP2D6 inhibition may reduce tamoxifen efficacy. Consider alternative antidepressant with little or no CYP2…
- Tamoxifen + Paroxetine Hydrochloride— Paroxetine's CYP2D6 inhibition may decrease tamoxifen efficacy. Consider alternative antidepressant with little or no CY…
- Tamoxifen + Paroxetine Hydrochloride Hemihydrate— Consider alternative antidepressant with little or no CYP2D6 inhibition due to paroxetine's effect on tamoxifen metaboli…
Moderate (9)
- Tamoxifen + Bexarotene— Bexarotene decreased tamoxifen plasma concentrations by approximately 35%, possibly through CYP3A4 induction.
- Tamoxifen + Bupropion Hcl Er (Xl)— Requires CYP2D6 activation for efficacy. Bupropion's CYP2D6 inhibition may reduce tamoxifen efficacy, potentially requir…
- Tamoxifen + Bupropion Hydrochloride— Drug requiring metabolic activation by CYP2D6 that may have reduced efficacy when coadministered with bupropion. Increas…
- Tamoxifen + Cyclophosphamide Injection, Solution— Concomitant use may increase risk of thromboembolic complications.
- Tamoxifen + Gadobenate Dimeglumine— MultiHance may compete for MOAT transporter and prolong systemic exposure of tamoxifen.
- Tamoxifen + Letrozole— Coadministration reduces letrozole plasma levels by 38% on average, but clinical experience indicates therapeutic effect…
- Tamoxifen + Letrozole Tablets— Coadministration reduces letrozole plasma levels by 38% on average, but clinical experience indicates therapeutic effect…
- Tamoxifen + Levothyroxine Sodium— May increase serum thyroxine-binding globulin concentration, resulting in initial transient increase in FT4 followed by …
- Tamoxifen + Liothyronine Sodium— May increase serum thyroxine-binding globulin concentration, altering T3 serum transport. Closely monitor thyroid hormon…
Minor (1)
- Tamoxifen + Ibandronate Sodium— No interaction observed between oral tamoxifen (30 mg) and intravenous ibandronate (2 mg).