{"id":"adjuvant-letrozole-postmenopausal-women","rwe":[],"tags":[],"safety":{"drugInteractions":[{"drug":"Warfarin","action":"Monitor","effect":"Increased risk of bleeding"},{"drug":"Phenytoin","action":"Monitor","effect":"Increased risk of phenytoin toxicity"},{"drug":"Rifampicin","action":"Avoid","effect":"Decreased letrozole levels"},{"drug":"Carbamazepine","action":"Avoid","effect":"Decreased letrozole levels"},{"drug":"Phenobarbital","action":"Avoid","effect":"Decreased letrozole levels"},{"drug":"St. John's Wort","action":"Avoid","effect":"Decreased letrozole levels"},{"drug":"Tamoxifen","action":"Avoid","effect":"Decreased efficacy of letrozole"},{"drug":"Aromatase inhibitors (e.g., anastrozole, exemestane)","action":"Monitor","effect":"Increased risk of adverse effects"}],"commonSideEffects":[],"contraindications":["You shouldn’t take letrozole if you are pregnant, trying to get pregnant, or if there is any chance that you could be pregnant."],"specialPopulations":{"Pregnancy":"May cause fetal harm. Embryotoxic, fetotoxic, and teratogenic in animals. Contraindicated in pregnancy. Test for pregnancy prior to initiation of the drug. Advise females of reproductive potential to use effective contraceptive methods during therapy and for ≥3 weeks after discontinuance of the drug. May impair female and male fertility.","Geriatric use":"No dosage adjustment necessary. Detailed Letrozole dosage information","Paediatric use":"Safety and efficacy not established in pediatric patients.","Renal impairment":"Clcr≥10 mL/minute: No dosage adjustment necessary.","Hepatic impairment":"Cirrhosis and severe hepatic impairment (Child-Pugh class C): Decrease dosage to 2.5 mg every other day. Mild to moderate hepatic impairment: No dosage adjustment recommended."}},"trials":[],"aliases":[],"company":"Pfizer","patents":[],"pricing":[],"_sources":{"trials":{"url":"https://clinicaltrials.gov/search?intr=adjuvant-letrozole-postmenopausal-women","method":"api_direct","source":"ClinicalTrials.gov","rawText":"","confidence":1,"sourceType":"ctgov","retrievedAt":"2026-04-19T23:55:44.809798+00:00"},"regulatory.ca":{"url":"","method":"api_direct","source":"Health Canada DPD","rawText":"","confidence":1,"sourceType":"health_canada_dpd","retrievedAt":"2026-04-19T23:55:51.204346+00:00"},"regulatory.eu":{"url":"","method":"api_direct","source":"European Medicines Agency","rawText":"","confidence":1,"sourceType":"ema_api","retrievedAt":"2026-04-19T23:55:44.837251+00:00"},"publicationCount":{"url":"https://pubmed.ncbi.nlm.nih.gov/?term=adjuvant-letrozole-postmenopausal-women","method":"api_direct","source":"PubMed/NCBI","rawText":"","confidence":1,"sourceType":"pubmed","retrievedAt":"2026-04-19T23:55:51.931653+00:00"},"mechanism.target_chembl":{"url":"","method":"api_direct","source":"ChEMBL mechanism: Cytochrome P450 19A1 inhibitor","rawText":"","confidence":1,"sourceType":"chembl","retrievedAt":"2026-04-19T23:55:52.536324+00:00"},"crossReferences.chemblId":{"url":"https://www.ebi.ac.uk/chembl/compound_report_card/CHEMBL1444/","method":"api_direct","source":"ChEMBL (EMBL-EBI)","rawText":"","confidence":1,"sourceType":"chembl","retrievedAt":"2026-04-19T23:55:52.433633+00:00"}},"allNames":"adjuvant letrozole (postmenopausal women)","offLabel":[],"timeline":[],"aiSummary":"Adjuvant letrozole is a marketed drug by Pfizer Inc. for postmenopausal women with hormone receptor-positive invasive breast cancer. 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