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)
Diabetes mellitus14.06.01.001; 05.06.01.0010.001317%Not Available
Diabetes mellitus inadequate control05.06.01.004; 14.06.01.0040.000263%Not Available
Diarrhoea07.02.01.001--
Dilatation ventricular02.04.02.0260.000395%Not Available
Diplopia17.17.01.005; 06.02.06.0020.000659%Not Available
Discomfort08.01.08.003--Not Available
Disseminated intravascular coagulation01.01.02.002; 24.01.01.0100.000659%
Disturbance in attention19.21.02.002; 17.03.03.0010.001633%
Dizziness02.11.04.006; 24.06.02.007; 17.02.05.003--
Drug eruption10.01.01.005; 08.01.06.015; 23.03.05.0010.001054%Not Available
Dry eye06.08.02.0010.000659%
Dry mouth07.06.01.0020.002239%
Dry skin23.03.03.0010.001054%
Dysaesthesia23.03.03.077; 17.02.06.0030.000263%
Dysgeusia17.02.07.003; 07.14.03.0010.001897%
Dyspepsia07.01.02.0010.002397%
Dysphagia07.01.06.0030.011143%
Dyspnoea22.02.01.004; 02.11.05.0030.010484%
Dyspnoea exertional02.11.05.005; 22.02.01.0050.000659%Not Available
Ectopic pregnancy18.02.02.0020.000527%Not Available
Eczema23.03.04.0060.000843%
Ejaculation failure21.03.01.0030.000263%Not Available
Electrolyte imbalance14.05.01.0020.000922%Not Available
Embolism venous24.01.01.003--Not Available
Endometrial adenocarcinoma21.07.02.011; 16.12.02.0030.000580%Not Available
Endometrial cancer21.07.02.002; 16.12.02.0010.000395%Not Available
Endometrial disorder21.07.01.001--Not Available
Endometrial hyperplasia21.07.01.002--Not Available
Eosinophilia01.02.04.0010.000527%
Epiphysiolysis15.02.02.002; 12.04.03.0030.000527%Not Available
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ADReCS-Target
Drug Name ADR Term Target
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