Adverse Drug Reaction Classification System

Pharmaceutical Information
Drug Name Letrozole
Drug ID BADD_D01257
Description Letrozole, or CGS 20267, is an oral non-steroidal type II aromatase inhibitor first described in the literature in 1990.[A190543,A1559,L11623,L11626] It is a third generation aromatase inhibitor like [exemestane] and [anastrozole], meaning it does not significantly affect cortisol, aldosterone, and thyroxine.[A190546] Letrozole was granted FDA approval on 25 July 1997.[L11623]
Indications and Usage Letrozole is indicated to treat postmenopausal women with hormone receptor (HR) positive early breast cancer, postmenopausal women with early breast cancer who have periviously been treated with tamoxifen, and postmenopausal women with HR+ or unknown advanced breast cancer.[L11623] Letrozole, given with ribociclib, is indicated to treat pre, peri, and postmenopausal women with HR+ and human epidermal growth factor 2 (HER2) negative advanced or metastatic breast cancer.[L11626]
Marketing Status approved; investigational
ATC Code L02BG04
DrugBank ID DB01006
KEGG ID D00964
MeSH ID D000077289
PubChem ID 3902
TTD Drug ID D0C1WH
NDC Product Code 58623-0099; 62135-491; 63629-7819; 71205-587; 69988-0014; 50268-476; 68554-0039; 16729-034; 51991-759; 59651-180; 63850-0025; 57884-0011; 65096-0116; 13808-514; 63592-3376; 65129-1130; 0078-0249; 55111-809; 63850-7723; 0093-7620; 42291-374; 71335-1526; 63850-7701; 55111-646
UNII 7LKK855W8I
Synonyms Letrozole | 4,4'-(1H-1,2,4-triazol-1-yl-methylene)-bis(benzonitrile) | CGS 20267 | CGS-20267 | CGS20267 | Femara | Fémara
Chemical Information
Molecular Formula C17H11N5
CAS Registry Number 112809-51-5
SMILES C1=CC(=CC=C1C#N)C(C2=CC=C(C=C2)C#N)N3C=NC=N3
Chemical Structure
ADRs Induced by Drug
*The priority for ADR severity classification is based on FAERS assessment, followed by the most severe level in CTCAE rating. If neither is available, it will be displayed as 'Not available'.
**The 'Not Available' level is hidden by default and can be restored by clicking on the legend twice..
ADR Term ADReCS ID ADR Frequency (FAERS) ADR Severity Grade (FAERS) ADR Severity Grade (CTCAE)
Tension19.06.02.0050.000922%Not Available
Therapeutic response decreased08.06.01.016--Not Available
Thinking abnormal19.10.03.001; 17.02.05.0230.000263%Not Available
Thirst14.03.02.007; 08.01.09.0210.000527%Not Available
Thrombocytopenia01.08.01.0020.003424%Not Available
Thrombophlebitis24.01.02.0010.000395%Not Available
Thrombotic stroke24.01.04.006; 17.08.01.021--Not Available
Thyroid disorder05.02.01.002--Not Available
Tooth disorder07.09.05.0010.000659%Not Available
Toothache07.09.06.0010.000263%
Toxic epidermal necrolysis12.03.01.015; 11.07.01.006; 10.01.01.006; 23.03.01.008--
Transient ischaemic attack24.04.06.005; 17.08.04.0010.001370%
Trigger finger15.07.01.0050.002028%Not Available
Tumour lysis syndrome16.32.03.002; 14.05.01.0040.000659%
Tumour pain16.32.03.003--
Type I hypersensitivity10.01.03.0060.000263%Not Available
Urethral disorder20.07.01.002--Not Available
Urinary tract disorder20.08.01.001--Not Available
Urinary tract infection20.08.02.001; 11.01.14.004--
Urticaria10.01.06.001; 23.04.02.001--
Uterine cancer21.07.02.003; 16.12.05.0010.000395%Not Available
Uterine leiomyoma21.07.02.004; 16.04.02.0010.000263%Not Available
Uveitis10.02.01.023; 06.04.03.0030.000659%
Vaginal discharge21.08.02.0020.000263%
Vaginal haemorrhage24.07.03.005; 21.08.01.001--
Vascular purpura01.01.04.007; 24.07.06.011; 23.06.01.0080.000659%Not Available
Vena cava thrombosis24.01.10.0010.000263%Not Available
Venous thrombosis24.01.01.0080.001054%Not Available
Ventricular extrasystoles02.03.04.0070.000527%Not Available
Ventricular tachycardia02.03.04.0100.000527%
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ADReCS-Target
Drug Name ADR Term Target
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