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Letrozole Tablets

Also known as: Letrozole

Aromatase InhibitorAromatase Inhibitors

Route: Oral

3 interactions on record

Letrozole Tablets has 3 known drug interactions based on U.S. FDA drug labeling data. Notable interactions include combinations with Tamoxifen. Patients taking Letrozole Tablets 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: 3
Moderate: 1
Minor: 2

Moderate (1)

Letrozole Tablets + Tamoxifen— Coadministration reduces letrozole plasma levels by 38% on average, but clinical experience indicates therapeutic effect…

Minor (2)

Letrozole Tablets + Cimetidine— Pharmacokinetic interaction study showed no clinically significant effect on letrozole pharmacokinetics.
Letrozole Tablets + Warfarin— Interaction study showed no clinically significant effect of letrozole on warfarin pharmacokinetics.

Letrozole Tablets + Tamoxifen🟡Moderate

Coadministration reduces letrozole plasma levels by 38% on average, but clinical experience indicates therapeutic effect of letrozole is not impaired when administered immediately after tamoxifen.

Letrozole Tablets + Cimetidine🟢Minor

Pharmacokinetic interaction study showed no clinically significant effect on letrozole pharmacokinetics.

Letrozole Tablets + Warfarin🟢Minor

Interaction study showed no clinically significant effect of letrozole on warfarin pharmacokinetics.

Contraindications

4 CONTRAINDICATIONS ● Pregnancy: Letrozole can cause fetal harm [see Use in Specific Populations (8.1) ] . ● Known hypersensitivity to the active substance, or to any of the excipients [see Adverse Reactions (6) ] . Pregnancy ( 4 ) Known hypersensitivity to the active substance, or to any of the excipients ( 4 )

Pregnancy & Breastfeeding

8.1 Pregnancy Risk S ummary Based on post-marketing reports, findings from animal studies and the mechanism of action, letrozole can cause fetal harm and is contraindicated for use in pregnant women. In post-marketing reports, use of letrozole during pregnancy resulted in cases of spontaneous abortions and congenital birth defects; however, the data are insufficient to inform a drug-associated risk [see Contraindications (4) , Warnings and Precautions (5.6) , Adverse reactions (6.2) , and Clinical Pharmacology (12.1) ] . In animal reproduction studies, administration of letrozole to pregnant animals during organogenesis resulted in increased post-implantation pregnancy loss and resorption, fewer live fetuses, and fetal malformation affecting the renal and skeletal systems in rats and rabbits at doses approximately 0.1 times the daily maximum recommended human dose (MRHD) on a mg/m 2 basis (see Data) . The background risk of major birth defects and miscarriage for the indicated population is unknown. However, the background risk in the U.S. general population of major birth defects is 2% to 4% and of miscarriage is 15% to 20% of clinically recognized pregnancies. Data Animal Data In a fertility and early embryonic development toxicity study in female rats, oral administration of letrozole starting 2 weeks before mating until pregnancy day 6 resulted in an increase in pre-implantation loss at doses ≥ 0.003 mg/kg/day (approximately 0.01 times the maximum recommended human dose on a mg/m 2 basis). In an embryo-fetal developmental toxicity study in rats, daily administration of oral letrozole during the period of organogenesis at doses ≥ 0.003 mg/kg (approximately 0.01 time the maximum recommended human dose on a mg/m 2 basis) resulted in embryo-fetal toxicity including intrauterine mortality, increased resorptions and postimplantation loss, decreased numbers of live fetuses and fetal anomalies including absence and shortening of renal papilla, dilation of ureter, edema

Data sourced from U.S. FDA drug labeling via openFDA and the NIH National Library of Medicine, supplemented with a small number of well-established interactions from curated clinical references. For informational purposes only. Always consult your pharmacist or physician.