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)
Abdominal distension07.01.04.0010.001712%
Abdominal pain07.01.05.0020.005426%
Abdominal tenderness07.01.05.0040.000527%Not Available
Abnormal weight gain14.03.02.0100.000395%Not Available
Abortion18.01.01.0010.000659%Not Available
Acute febrile neutrophilic dermatosis01.02.01.006; 23.03.03.0330.001185%Not Available
Acute myeloid leukaemia16.01.05.001; 01.10.05.0010.000922%Not Available
Acute myocardial infarction24.04.04.001; 02.02.02.0010.000659%Not Available
Acute respiratory failure22.02.06.001; 14.01.04.0040.000527%Not Available
Adenocarcinoma16.16.01.0040.000263%Not Available
Affective disorder19.04.04.0010.000711%Not Available
Alopecia23.02.02.0010.010879%
Amnesia19.20.01.001; 17.03.02.0010.001633%
Amyotrophic lateral sclerosis17.05.05.0040.000263%Not Available
Anaemia01.03.02.0010.006111%
Anaphylactic reaction24.06.03.006; 10.01.07.001--
Anaphylactic shock24.06.02.004; 10.01.07.002--Not Available
Angina pectoris24.04.04.002; 02.02.02.002--
Angioedema22.04.02.008; 23.04.01.001; 10.01.05.009--Not Available
Ankylosing spondylitis15.01.09.001; 10.04.04.0040.000659%Not Available
Anxiety19.06.02.002--
Aortic aneurysm24.02.03.0010.000527%Not Available
Aortic stenosis24.04.01.001--Not Available
Aortic thrombosis24.01.09.0010.001185%Not Available
Aphasia19.21.01.001; 17.02.03.0010.000790%
Aphthous ulcer07.05.06.0020.000843%Not Available
Arrhythmia02.03.02.0010.002107%Not Available
Arrhythmia supraventricular02.03.03.0010.000659%Not Available
Arterial thrombosis24.01.01.002--Not Available
Arteriosclerosis24.04.02.0010.000659%Not Available
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ADReCS-Target
Drug Name ADR Term Target
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