Letrozole 2.5mg/5ml oral suspension
Requires a prescription from a doctor or prescriber
Official documents, adverse reaction reporting, and safety monitoring
Report a side effect
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Official medicine documents
Yellow Card
Report side effects (MHRA)
Drug safety updates
MHRA alerts for Letrozole
Safety monitoring data
Yellow Card reports
The MHRA Yellow Card scheme collects reports of suspected side effects from healthcare professionals and patients. View the Drug Analysis Profile (iDAP) for real-world adverse reaction data.
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Suspected adverse reactions reported for Letrozole
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Interactive Drug Analysis Profiles for all medicines
Report a side effect
Submit a Yellow Card report to the MHRA
Data from the MHRA Yellow Card scheme. A reported reaction does not necessarily mean the medicine caused it. Contains public sector information licensed under the Open Government Licence v3.0.
EudraVigilance
The European Medicines Agency (EMA) collects suspected adverse reaction reports from across the EU/EEA through the EudraVigilance system. Search for safety data on this medicine.
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Suspected adverse reactions reported for Letrozole
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EudraVigilance data is published by the European Medicines Agency (EMA). A suspected adverse reaction is not necessarily caused by the medicine.
1 branded products available
WHO defined daily dose (DDD)
2.5 mg
Not a recommended dose. The DDD is the assumed average maintenance dose per day for a drug used for its main indication in adults. It is a statistical measure used for research and comparison purposes only.
Source: WHO Collaborating Centre for Drug Statistics Methodology, distributed via the NHS dm+d supplementary mapping files (NHSBSA). Contains public sector information licensed under the Open Government Licence v3.0.
Therapeutically similar medicines
Tablets & capsules
(4)Similarity is based on WHO Anatomical Therapeutic Chemical (ATC) classification and on a factual NHS dm+d therapeutic-grouping code prefix. Source data: NHS dm+d via TRUD (OGL v3.0), WHO ATC/DDD Index.
NHS prescribing volume and spending trends
Guidelines from the National Institute for Health and Care Excellence
NICE clinical guidance(10)
Ribociclib with an aromatase inhibitor for previously untreated, hormone receptor-positive, HER2-negative, locally advanced or metastatic breast cancer (TA496)
Palbociclib with an aromatase inhibitor for previously untreated, hormone receptor-positive, HER2-negative, locally advanced or metastatic breast cancer (TA495)
Fulvestrant for untreated locally advanced or metastatic oestrogen-receptor positive breast cancer (TA503)
Fulvestrant for the treatment of locally advanced or metastatic breast cancer (TA239)
Abemaciclib with an aromatase inhibitor for previously untreated, hormone receptor-positive, HER2-negative, locally advanced or metastatic breast cancer (TA563)
Lapatinib or trastuzumab in combination with an aromatase inhibitor for the first-line treatment of metastatic hormone receptor-positive breast cancer that overexpresses HER2 (TA257)
Ribociclib with an aromatase inhibitor for adjuvant treatment of hormone receptor-positive HER2-negative early breast cancer at high risk of recurrence (TA1086)
Elacestrant for treating oestrogen receptor-positive HER2-negative advanced breast cancer with an ESR1 mutation after endocrine treatment (TA1036)
Ribociclib with fulvestrant for treating hormone receptor-positive, HER2-negative advanced breast cancer after endocrine therapy (TA687)
Everolimus with exemestane for treating advanced breast cancer after endocrine therapy (TA421)
Source: National Institute for Health and Care Excellence (NICE). Contains public sector information licensed under the Open Government Licence v3.0.
Check stock at pharmacies and supply information
Pharmacy stock checkers
Search for this medicine at major UK pharmacy chains. These links open the retailer's own website — results depend on their current online catalogue.
Supply & safety information
Official UK regulator monitoring and safety alerts
Pharmacy links redirect to the retailer's own search and do not represent real-time stock levels. Shortage and safety information sourced from MHRA drug safety updates (gov.uk, Crown Copyright under OGL v3.0).
Codes for healthcare professionals and prescribing systems
These codes are used by healthcare IT systems and prescribers to identify this medicine.
NHS UK identifiers
Browse tools
SNOMED CT and dm+d codes from NHS TRUD (Technology Reference data Update Distribution), licensed under the Open Government Licence v3.0. ATC codes from the WHO Collaborating Centre for Drug Statistics Methodology (whocc.no).
Active and completed clinical studies from ClinicalTrials.gov
Source: ClinicalTrials.gov, a database of the U.S. National Library of Medicine (NLM), National Institutes of Health (NIH). Data accessed via ClinicalTrials.gov API v2. Trial information is provided for research purposes and does not constitute medical advice.
Academic studies and reviews for this medicine's active substance
Showing the 50 most relevant studies.
Reviews & meta-analyses: 15 · Randomised trials: 28 · 2016–2026
Showing the 50 most relevant studies, sorted by most relevant.
S. Johnston, S. Puhalla, D. Wheatley, et al.
Journal of clinical oncology : official journal of the American Society of Clinical Oncology, 2019
R. Finn, J. Crown, J. Ettl, et al.
Breast Cancer Research : BCR, 2016
A. Prat, C. Saura, T. Pascual, et al.
The Lancet. Oncology, 2019
Saad Amer, J. Smith, Ahmad E. Mahran, et al.
Human Reproduction (Oxford, England), 2017
Zhuo Liu, Yuli Geng, Yan-Jiao Huang, et al.
Obstetrics & Gynecology, 2023
R. Mistry, J. May, G. Suri, et al.
Journal of Managed Care & Specialty Pharmacy, 2018
E. Mamounas, H. Bandos, B. Lembersky, et al.
The Lancet. Oncology, 2019
S. Franik, Stephanie Eltrop, J. Kremer, et al.
The Cochrane database of systematic reviews, 2018
A. DeMichele, M. Cristofanilli, A. Brufsky, et al.
Breast Cancer Research : BCR, 2021
Yanting Sun, Jun Wang, Guofeng Chen
Gynecological Endocrinology, 2025
Sources: aggregated from Europe PMC (EMBL-EBI), OpenAlex, Crossref, PubMed and other open scholarly databases. Retracted articles are excluded. Study information is provided for research purposes and does not constitute medical advice.
Pharmacology and chemical data from DrugBank
Key facts
Drug status
Approved
Major interactions
83 found
Half-life
42h
Mechanism
Letrozole is a non-steroidal type II aromatase inhibitor.
Food interactions
1 warning
Human targets
1 target
Data: DrugBank · CC BY-NC 4.0
Pharmacokinetics at a glance
Absorption
99.9%
[A190546]
A 2.5mg oral dose reaches a Cmax of 104nmol/L with a Tmax of 8.10h,…
Half-life
42h
[A190546][A190555][L11623]
…
Protein binding
60%
[A190546][A190555]
55% is bound to albumin.
[A190546]
Volume of distribution
1.87L/kg
[A190546]
Metabolism
[A33288]
…
Elimination
90%
[L11623]
75% of the dose is recovered as a glucuronide metabolite, 9% is in the form of the ketone and…
Clearance
1.52L/h
[A190555]
Pharmacokinetic data: DrugBank · CC BY-NC 4.0
Letrozole was granted FDA approval on 25 July 1997.[L11623]
[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]
Known interactions with other medicines. Always consult a healthcare professional.
Showing 50 of 377 interactions
[L11623]
Animal studies do not report serious adverse effects with high dose treatment.
[A190564]
Patients experiencing and overdose should be treated with symptomatic and supportive measures.
[L11623]
Oral doses over 2000mg/kg were associated with reduced motor activity, ataxia, dyspnea, and death in mice and rats.
[L11623]
Letrozole is a third generation type II aromatase inhibitor used to treat estrogen dependant breast cancers.[L11623] It has a long duration of action as it has a half life of over 42 hours in breast cancer patients.[A190546][A190555][L11623] Patients should be counselled regarding the risk of interstitial lung disease, pneumonitis, QT prolongation, elevated transaminase levels, neutropenia, and embryo-fetal toxicity.[L11623]
How the body processes this drug — absorption, distribution, metabolism, and elimination
[A190546]
A 2.5mg oral dose reaches a Cmax of 104nmol/L with a Tmax of 8.10h, and an AUC of 7387nmol\*h/L.
[A190555]
[A190546][A190555][L11623]
[A190546][A190555]
55% is bound to albumin.
[A190546]
[A190546]
[A33288]
4,4'-(hydroxymethylene)dibenzonitrile is glucuronidated by UGT2B7.
[A190549]
[L11623]
75% of the dose is recovered as a glucuronide metabolite, 9% is in the form of the ketone and carbinol metabolites, and 6% is recovered in urine as unchanged letrozole.
[A33288][L11623]
[A190555]
Proteins and enzymes this drug interacts with in the body
PMID:27702664 PMID:2848247
Catalyzes three successive oxidations of C19 androgens: two conventional oxidations at C19 yielding 19-hydroxy and 19-oxo/19-aldehyde derivatives, followed by a third oxidative aromatization step that involves C1-beta hydrogen abstraction combined with cleavage of the C10-C19 bond to yield a phenolic A ring and formic acid .
PMID:20385561
Alternatively, the third oxidative reaction yields a 19-norsteroid and formic acid. Converts dihydrotestosterone to delta1,10-dehydro 19-nordihydrotestosterone and may play a role in homeostasis of this potent androgen .
PMID:22773874
Also displays 2-hydroxylase activity toward estrone .
PMID:22773874
Mechanistically, uses molecular oxygen inserting one oxygen atom into a substrate, and reducing the second into a water molecule, with two electrons provided by NADPH via cytochrome P450 reductase (CPR; NADPH-ferrihemoprotein reductase) PMID:20385561 PMID:22773874
Enzymes involved in drug metabolism — important for understanding drug interactions
Proteins that transport this drug across cell membranes
PMID:2897240 PMID:35970996 PMID:8898203 PMID:9038218 PMID:35507548
Catalyzes the flop of phospholipids from the cytoplasmic to the exoplasmic leaflet of the apical membrane. Participates mainly to the flop of phosphatidylcholine, phosphatidylethanolamine, beta-D-glucosylceramides and sphingomyelins .
PMID:8898203
Energy-dependent efflux pump responsible for decreased drug accumulation in multidrug-resistant cells PMID:2897240 PMID:35970996 PMID:9038218
Proteins that carry this drug through the body
PMID:19021548
Major calcium and magnesium transporter in plasma, binds approximately 45% of circulating calcium and magnesium in plasma (By similarity).
Potentially has more than two calcium-binding sites and might additionally bind calcium in a non-specific manner (By similarity). The shared binding site between zinc and calcium at residue Asp-273 suggests a crosstalk between zinc and calcium transport in the blood (By similarity). The rank order of affinity is zinc > calcium > magnesium (By similarity).
Binds to the bacterial siderophore enterobactin and inhibits enterobactin-mediated iron uptake of E.coli from ferric transferrin, and may thereby limit the utilization of iron and growth of enteric bacteria such as E.coli .
PMID:6234017
Does not prevent iron uptake by the bacterial siderophore aerobactin PMID:6234017
ATC L02BG04
Chemical identifiers
CAS, UNII, InChI Key and database cross-references
Show
Chemical identifiers
CAS, UNII, InChI Key and database cross-references
Linked compound data from DrugBank Open Data (CC BY-NC 4.0)
Letrozole
Additional database identifiers
Drugs Product Database (DPD)
11446
ChemSpider
3765
BindingDB
13061
ZINC
ZINC000003778874
HUGO Gene Nomenclature Committee (HGNC)
HGNC:2594
GenAtlas
CYP19A1
GeneCards
CYP19A1
GenBank Gene Database
M22246
GenBank Protein Database
179002
Guide to Pharmacology
1362
UniProt Accession
CP19A_HUMAN
HUGO Gene Nomenclature Committee (HGNC)
HGNC:2621
GeneCards
CYP2C19
GenBank Gene Database
M61854
GenBank Protein Database
181344
Guide to Pharmacology
1328
UniProt Accession
CP2CJ_HUMAN
HUGO Gene Nomenclature Committee (HGNC)
HGNC:12554
GeneCards
UGT2B7
GenBank Gene Database
J05428
GenBank Protein Database
340080
UniProt Accession
UD2B7_HUMAN
HUGO Gene Nomenclature Committee (HGNC)
HGNC:2637
GenAtlas
CYP3A4
GeneCards
CYP3A4
GenBank Gene Database
M18907
Guide to Pharmacology
1337
UniProt Accession
CP3A4_HUMAN
HUGO Gene Nomenclature Committee (HGNC)
HGNC:2610
GenAtlas
CYP2A6
GeneCards
CYP2A6
GenBank Gene Database
X13897
Guide to Pharmacology
1321
UniProt Accession
CP2A6_HUMAN
HUGO Gene Nomenclature Committee (HGNC)
HGNC:2594
GenAtlas
CYP19A1
GeneCards
CYP19A1
GenBank Gene Database
M22246
GenBank Protein Database
179002
Guide to Pharmacology
1362
UniProt Accession
CP19A_HUMAN
HUGO Gene Nomenclature Committee (HGNC)
HGNC:399
GenAtlas
ALB
GeneCards
ALB
GenBank Gene Database
V00494
GenBank Protein Database
28590
UniProt Accession
ALBU_HUMAN
HUGO Gene Nomenclature Committee (HGNC)
HGNC:40
GenAtlas
ABCB1
GeneCards
ABCB1
GenBank Gene Database
M14758
GenBank Protein Database
307180
Guide to Pharmacology
768
UniProt Accession
MDR1_HUMAN
DrugBank citations
If you use DrugBank data in your research, please cite:
- DrugBank 6.02024Recommended citationKnox C., Wilson M., Klinger C.M., et alDrugBank 6.0: the DrugBank Knowledgebase for 2024Nucleic Acids Res. 2024 Jan 552(D1):D1265-D1275
- DrugBank 5.02018Wishart D.S., Feunang Y.D., Guo A.C., et alDrugBank 5.0: a major update to the DrugBank database for 2018Nucleic Acids Res. 2017 Nov 846(D1):D1074-D1082
- DrugBank 4.02014Law V., Knox C., Djoumbou Y., et alDrugBank 4.0: shedding new light on drug metabolismNucleic Acids Res. 2014 Jan 142(1):D1091-7
- DrugBank 3.02011Knox C., Law V., Jewison T., et alDrugBank 3.0: a comprehensive resource for 'omics' research on drugsNucleic Acids Res. 2011 Jan39(Database issue):D1035-41
- DrugBank 2.02008Wishart D.S., Knox C., Guo A.C., et alDrugBank: a knowledgebase for drugs, drug actions and drug targets.Nucleic Acids Research2008 Jan36(Database issue):D901-6
- DrugBank 1.02006Wishart D.S., Knox C., Guo A.C., et alDrugBank: a comprehensive resource for in silico drug discovery and exploration.Nucleic Acids Research2006 Jan 134(Database issue):D668-72