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)
Scleritis10.02.01.025; 06.04.07.0020.000263%Not Available
Scleroderma23.03.02.005; 15.06.01.002; 10.04.07.0010.000263%Not Available
Scoliosis15.10.04.0010.000580%
Second primary malignancy16.16.01.0140.004083%
Sensory disturbance17.02.07.0060.000843%Not Available
Sjogren's syndrome15.06.01.015; 10.04.04.009; 07.06.01.010; 06.08.02.0110.001054%Not Available
Skin discolouration23.03.03.0050.000790%Not Available
Skin disorder23.03.03.007--Not Available
Skin lesion23.03.03.0100.000527%Not Available
Skin ulcer24.04.03.007; 23.07.03.0030.000659%
Small intestinal obstruction07.13.06.0010.000922%
Somnolence19.02.05.003; 17.02.04.006--
Speech disorder22.12.03.027; 19.19.02.002; 17.02.08.0030.000659%Not Available
Spinal osteoarthritis15.01.04.0030.000263%Not Available
Splenic infarction24.04.08.024; 01.09.02.0040.000790%Not Available
Splenomegaly01.09.02.0010.000263%Not Available
Stomatitis07.05.06.005--
Stridor22.04.02.0030.000263%
Subarachnoid haemorrhage24.07.04.004; 17.08.01.010; 12.01.10.0110.001054%Not Available
Suicidal ideation19.12.01.0030.002107%
Superior vena cava syndrome24.04.09.008; 16.32.03.0190.000263%
Swelling face23.04.01.018; 08.01.03.100; 10.01.05.0180.001317%Not Available
Swollen tongue10.01.05.015; 07.14.02.003; 23.04.01.0140.000843%Not Available
Syncope02.11.04.015; 24.06.02.012; 17.02.04.0080.001844%
Synovitis15.04.02.0010.000263%Not Available
Tachycardia02.03.02.0070.004399%Not Available
Tachypnoea22.02.01.0140.001054%Not Available
Tendon disorder12.01.07.019; 15.07.01.0020.000527%Not Available
Tendonitis12.01.07.007; 15.07.01.0030.001633%Not Available
Tenosynovitis15.07.01.0040.000395%Not Available
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ADReCS-Target
Drug Name ADR Term Target
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