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Letrozole Specifar

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Letrozole Specifar

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Medically reviewed

Laura Arias

Last updated on 22/12/2025

This page provides general, reference-level information compiled from official medical sources. It is not a substitute for professional medical advice, diagnosis, or treatment. For decisions about your health, please consult a qualified healthcare professional.

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Overview of Letrozole Specifar

Property Description
Active Ingredient Letrozole (INN)
Form Oral Tablet
Pharmacological Class Nonsteroidal Aromatase Inhibitor (AI)
General Purpose Achieving Estrogen Reduction
Origin / Type Synthetic Triazole Derivative

Letrozole Specifar is a synthetic, prescription-only medicine manufactured by Specifar Pharmaceuticals and supplied as an oral tablet for oral administration. The active ingredient is Letrozole (INN), which belongs to the class of third-generation nonsteroidal aromatase inhibitors (AI), a designation that defines its specific mechanism of interfering with the body's hormone production. The structural composition of Letrozole is a triazole derivative, which underpins its high potency and specificity within its pharmacological class.

The core function of Letrozole is to achieve a significant and sustained reduction of estrogen levels in the body, providing a powerful antiestrogen action. This physiological action is accomplished through selective enzyme inhibition: the drug competitively blocks the aromatase enzyme (CYP19A1), which is the enzyme responsible for converting precursor androgens into active estrogens (e.g., estradiol). By successfully blocking this enzyme, the medicine ensures a profound reduction in circulating estrogen, serving the general purpose of suppressing hormonal support for hormone-sensitive cells.

Pharmacological studies have established the high specificity of this nonsteroidal agent as a differentiating factor. This mechanism ensures that the required suppression of the aromatase enzyme is achieved without detrimentally affecting the production of other essential adrenal steroids, such as glucocorticoids. This highly selective and reversible binding characteristic ensures that the drug is a targeted agent for estrogen synthesis inhibition.

Regulatory References

  1. National Cancer Institute, NIH
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What side effects are possible with Letrozole Specifar?

Possible Side Effects and Safety Information

Letrozole Specifar is associated with an official safety profile that highlights specific adverse reactions, primarily related to its mechanism of reducing estrogen levels. The most frequently reported adverse reactions (ge 10% incidence), classified as Very Common, include hot flashes, hypercholesterolemia (high cholesterol), arthralgia (joint pain), fatigue, and increased sweating.

Serious and Clinically Significant Adverse Reactions

Safety data indicate a higher incidence of osteoporosis and bone fractures in patients receiving letrozole compared to a comparator (tamoxifen or placebo), emphasizing the need for bone mineral density monitoring. Cardiovascular events such as thromboembolic events, myocardial infarction (heart attack), and angina pectoris are also documented as potential risks.

Frequency Classification Key Adverse Reactions (Examples)
Very Common (ge 1/10) Hot flashes, hypercholesterolemia, arthralgia, fatigue, increased sweating.
Common (ge 1/100 to <1/10) Headache, dizziness, depression, nausea, vomiting, bone pain, hypertension.
Uncommon (ge 1/1000 to <1/100) Ischaemic cardiac events, cerebrovascular accident, leukopenia, cataract.

Safety Restrictions and Monitoring

The drug is contraindicated in women who are or may become pregnant due to the confirmed risk of embryo-fetal toxicity, including spontaneous abortions and congenital birth defects. Females of reproductive potential must use effective contraception during treatment and for a period after the last dose. Due to reports of fatigue, dizziness, and somnolence, caution is advised when operating machinery or driving until the individual's reaction to the medication is known. Regular monitoring of serum cholesterol and bone mineral density is recommended during treatment.

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Overdose and Emergency Response

In the event of a suspected or known overdose of Letrozole Specifar, immediate medical attention is required. You must contact the nearest hospital casualty department or a National Poisons Information Centre without delay, as explicitly stated in the regulatory guidance.

Documented Overdose Scope

Official regulatory information states that the clinical data concerning Letrozole overdose is limited to isolated case reports. The highest single dose reported ingested in these cases was 62.5 mg (equivalent to 25 tablets of 2.5 mg). In the documented cases, no specific serious adverse reactions were reported, meaning the full extent of clinical manifestations following a large overdose is not firmly established in the labeling.

Management and Treatment Measures

Due to the limited evidence base, no specific antidote is known or available for Letrozole overdose. Treatment is officially defined as symptomatic and supportive.

Procedural steps officially described for managing an acute ingestion include:

  • Frequent monitoring of vital signs is considered appropriate in the management plan.
  • The induction of emesis (vomiting) may be considered by medical professionals if the patient is alert.

Regulatory guidelines confirm that no specific population-based considerations for overdose management are cited, and treatment recommendations are constrained to essential supportive care.

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Therapeutic Uses of Letrozole Specifar

Letrozole Specifar is a therapeutic option designated for the management of certain types of breast cancer in postmenopausal women. The medication is utilized in several distinct clinical situations, serving a role in different stages of the condition.

Quick Facts: Therapeutic Uses

  • Adjuvant Treatment: Used following initial treatment, such as surgery, for early breast cancer that is hormone receptor-positive.
  • Extended Adjuvant Treatment: Employed in postmenopausal women who have completed five years of standard tamoxifen therapy for early breast cancer.
  • Advanced Breast Cancer: Indicated as a first-line treatment for advanced, locally advanced, or metastatic breast cancer that is hormone receptor-positive or of unknown status. It is also used to address advanced breast cancer in individuals who have experienced disease progression following previous antiestrogen therapy.

Letrozole Specifar is part of the established approach to hormone-sensitive cancers and may be considered a component of long-term care. The primary goal of use in these contexts is to address the growth and progression of hormone-sensitive malignant cells.

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Eligibility and Restrictions for Use

Eligibility Scope

Letrozole Specifar is officially permitted for use only in postmenopausal women. Standard eligibility is maintained for adults, including older adults, and for patients with standard levels of renal impairment (creatinine clearance ge 10 mL/ min). Use in the pediatric population (children and adolescents le 17 years) is not recommended because safety and efficacy have not been established.

Contraindications and Restrictions

The medicine is contraindicated in several key populations:

  • Women with premenopausal endocrine status.
  • Women who are or may become pregnant or who are breast-feeding.
  • Patients with a known hypersensitivity to the active substance (Letrozole) or to any of the excipients.

Standard use is prohibited in patients with severe hepatic impairment (Child-Pugh C) due to significantly increased drug exposure; conditional use requires close medical supervision. Use is also not recommended for individuals with specific hereditary metabolic disorders (e.g., galactose intolerance, lactase deficiency). Women of childbearing potential must use effective contraception during and shortly after treatment.

Eligibility Classifications

Eligibility severity classification (as defined in official documents): Contraindicated; Not Recommended; Restricted Use (Conditional); Allowed (Standard Use).

Connection to the overall eligibility profile: Official regulatory documents establish absolute prohibitions based on reproductive status and known hypersensitivity. Eligibility is primarily conferred upon postmenopausal women, with restricted or conditional use strictly defined by specific organ-function limitations, such as severe hepatic impairment. The profile clearly outlines who is permitted or prohibited from using the medicine.

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What should I know about interactions with other medicines?

Interactions with other medicines and products

The official regulatory profile for Letrozole establishes specific restrictions and documented exposure changes when co-administered with certain substances. The primary constraint is the required avoidance of co-administration with Tamoxifen, other anti-estrogens, or estrogen-containing therapies. This restriction is due to the potential for these agents to counteract the medicine’s function, resulting in a diminution of the pharmacological action and a documented reduction in Letrozole plasma levels.

Metabolic interactions are documented through the primary clearance pathways, CYP3A4 and CYP2A6. Strong inhibitors of CYP3A4 (such as Ketoconazole or Voriconazole) are expected to increase systemic exposure to Letrozole by reducing its clearance. Conversely, strong inducers of CYP3A4 (including the herbal product St. John's Wort) may decrease plasma concentrations. Caution is indicated when Letrozole is co-administered with medicinal products having a narrow therapeutic index that are dependent on CYP2C19 for metabolism.

Regarding constraints related to physiological factors, regulatory data confirms that patients with severe hepatic impairment (Child-Pugh C) exhibit approximately twice the systemic exposure compared to healthy individuals. Official regulatory documents also state that the absorption of Letrozole is not affected by food.

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Mechanism of Action

Letrozole's action is defined by its ability to create a state of profound estrogen deprivation through a specific molecular mechanism, targeting the production of the hormone rather than its action at the receptor level.

Inhibition of Aromatase Enzyme

The primary mechanism involves acting as a nonsteroidal competitive inhibitor of the Aromatase enzyme (CYP19A1) in peripheral tissues. By binding reversibly to the enzyme's active site, Letrozole physically blocks the metabolic conversion of precursor androgens into active estrogens (e.g., estradiol). This molecular intervention initiates the mechanistic cascade, leading to the reduction of estrogen synthesis throughout the body.


Systemic Estrogen Deprivation and Feedback Modulation

The blockade of Aromatase results in a dramatic reduction in circulating plasma estrogen levels. This creates a functional antiestrogen environment, which is the resulting physiological consequence. Furthermore, the lack of systemic estrogen removes the usual negative feedback signal to the pituitary gland, leading to a compensatory, secondary increase in the release of gonadotropins such as Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH).

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Dosage and Administration Information

Official Dosing and Administration Protocol

Letrozole Specifar is a medicine intended for oral administration as a film-coated tablet. The official usage protocol is centered on a fixed, standardized daily dose of 2.5 mg for all approved indications in postmenopausal women. This dosage is administered once daily (q.d.), establishing a continuous treatment schedule that is maintained over a long term, often extending for several years in the adjuvant setting or continuing until the progression of the disease is noted.

Administration Conditions and Timing

To ensure flexible and consistent use, the tablet may be ingested with or without food because the presence of a meal does not affect the drug's absorption. The medicine should be swallowed whole with a liquid. Adherence to the once-daily schedule is critical, and official instructions provide clear guidance for handling timing lapses. If the daily administration is missed, the dose should be taken immediately upon remembering, unless it is almost time for the next scheduled dose. In such a scenario, the missed dose must be skipped, and the patient must not take a double dose to compensate.

No dosage adjustment is required for patients with mild to moderate renal or hepatic impairment, defining a consistent 2.5 mg regimen for these specific patient populations.

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Recent Clinical Evidence

Research evidence / Overview of studies for Letrozole Specifar

Evidence for Adjuvant Treatment of Early Breast Cancer

The research base for Letrozole consists primarily of large-scale, multi-center, randomized controlled trials (RCTs). These studies were designed to examine the agent’s use following initial treatments such as surgery for postmenopausal women diagnosed with early-stage, hormone receptor-positive breast cancer. Researchers in these trials primarily monitored two key outcomes over several years: Disease-Free Survival (DFS) and Overall Survival (OS). Studies often compared Letrozole against the hormonal agent Tamoxifen, which was another treatment option.

Evidence for Extended Adjuvant Treatment

The evidence supporting the extended use of Letrozole after a patient has completed five years of initial hormonal therapy is primarily based on large, randomized, double-blind, placebo-controlled trials. This research monitored thousands of postmenopausal women who were disease-free after completing their prior therapy. The key outcomes studied included Disease-Free Survival (DFS) and Distant Disease-Free Survival (DDFS), which measures the time until the cancer returns in an area far from the original site. The initial reports characterized the observed patterns in disease recurrence events and survival endpoints between the treatment groups.

Evidence for Advanced and Metastatic Breast Cancer

Letrozole has been evaluated for the management of locally advanced or metastatic breast cancer that is hormone receptor-positive in postmenopausal women. The evidence here comes from randomized controlled trials that used Letrozole as a single agent for initial (first-line) treatment and in patients whose disease had progressed following previous antiestrogen therapy. Key outcomes monitored included the Objective Response Rate (ORR), which measures the percentage of patients whose tumors shrank by a defined amount, and Time to Progression (TTP), which tracks the length of time before the disease worsens.

Evidence Gaps and Areas of Uncertainty

One area of research that remains limited is the number of large-scale trials that directly compare Letrozole head-to-head against the other two third-generation aromatase inhibitors across all indications. Furthermore, the optimal total duration of extended therapy is not fully established by current research. In the extended adjuvant setting, the analysis of long-term overall survival required complex statistical adjustments due to patient crossover between the treatment and placebo groups.

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Frequently Asked Questions (FAQ)

Common questions about Letrozole Specifar (FAQ)

Q: What is the main difference between Letrozole Specifar and Tamoxifen?

Studies and official information indicate that Letrozole and Tamoxifen belong to different pharmacological classes. Letrozole is a nonsteroidal aromatase inhibitor, which works by blocking the production of estrogen. Tamoxifen is a a selective estrogen receptor modulator (SERM), which works by blocking estrogen's action at the receptor. Official documents state that co-administration of the two agents is restricted, as it may diminish the action of Letrozole.


Q: How long does it usually take for Letrozole Specifar to start having an effect?

Regulatory information indicates that Letrozole is absorbed quickly after it is taken. However, it takes time to reach a therapeutic concentration in the blood. Official documents state this steady-state concentration, where the amount of drug entering the body equals the amount leaving, is usually achieved after daily dosing in approximately two to six weeks.


Q: What happens if I miss taking a tablet of Letrozole Specifar?

Regulatory documents indicate the missed dose should be taken immediately upon remembering, unless it is almost time for the next scheduled dose. If the time is close to the next scheduled dose, regulatory instructions state that the missed dose should be skipped, and a double dose should not be taken to compensate.


Q: Can Letrozole Specifar interact with common over-the-counter pain relievers?

Official regulatory documents primarily warn about interactions with medicines that strongly interfere with the drug's metabolism in the liver. Regulatory documents do not specifically list common OTC pain relievers as restricted; however, official patient information advises checking with a healthcare professional regarding all medications and supplements.


Q: Is it common to experience dizziness or headaches with Letrozole Specifar?

Yes, official safety profiles list headache and dizziness as Common adverse reactions. This means these effects are documented to occur in between 1 in 100 people and 1 in 10 people (ge 1/100 to <1/10) who take the medicine, according to regulatory data.


Q: Is it safe to drive while I am taking Letrozole Specifar?

Regulatory guidance advises caution when operating machinery or driving. This is because official documents report side effects such as fatigue, dizziness, and somnolence (sleepiness). Patients are generally advised to wait until an individual’s reaction to the medicine is known.


Q: Are there any known interactions between Letrozole Specifar and supplements?

Regulatory documents explicitly mention that the herbal product St. John's Wort may reduce the medicine's concentration in the body and should be avoided. Official patient information recommends telling a healthcare provider about all medicines, vitamins, and supplements being taken, as they may interact with the drug’s metabolism.


Q: What is the half-life of Letrozole as described in official documents?

The half-life refers to the time it takes for half of the drug to be eliminated from the body. Official regulatory information states that the terminal elimination half-life of Letrozole is approximately 2 days (42 hours). This half-life supports the medicine’s classification as a once-daily drug.


Q: How is the interaction with alcohol described in patient information for Letrozole Specifar?

Official patient information generally states that there is no evidence that drinking alcohol causes problems when taking Letrozole. However, official guidance notes that some individuals may experience a worsening of existing side effects, such as hot flashes, when consuming alcohol.


Q: Does the drug label mention anything about how to handle sun exposure while on Letrozole Specifar?

Official regulatory documents do not list photosensitivity (increased sensitivity to the sun) as a common or serious adverse reaction. Patient guidance notes primarily focus on proper storage of the tablets away from sunlight. No specific handling instructions for sun exposure while taking the medicine are provided in the regulatory labels.


Q: Are there common reasons why a doctor might change a patient from Tamoxifen to Letrozole Specifar?

Regulatory studies provide evidence supporting a sequential strategy, often implemented after initial Tamoxifen therapy is completed. This strategy is examined in studies for potentially reducing the risk of cancer recurrence. A change may also be considered due to a comparison of safety profiles regarding certain risks, such as venous thromboembolic events.


Q: Does taking Letrozole Specifar cause weight gain?

Official safety data confirms that weight changes are reported as an adverse reaction in clinical trials. This is officially classified as a side effect reported in a small percentage of patients. The incidence is generally low in comparison to some other hormonal therapies.


Q: Are there different strengths of Letrozole Specifar tablets available?

Regulatory databases and official monographs state that the approved and marketed strength for Letrozole is a 2.5 mg film-coated tablet. This single dose is used for all approved indications in postmenopausal women. The drug is not typically approved or supplied in other strengths for this population.


Q: What is the standard duration of treatment mentioned in clinical guidelines for Letrozole Specifar?

Official regulatory documents define the standard duration based on study evidence. For early breast cancer, the initial period is typically 5 years in the adjuvant setting. For extended adjuvant treatment, which follows initial therapy, the duration may be longer, often an additional 5 years, for up to 10 years total.


Q: What are the key points to discuss with a healthcare provider about Letrozole Specifar?

Key points, as stated in official warnings and monitoring requirements, include any history of osteoporosis or fractures, any existing cardiovascular risk factors (such as high blood pressure or cholesterol), and the concurrent use of all other medicines and supplements.


Q: Do studies show a difference in side effects based on age while taking Letrozole Specifar?

While clinical studies included a broad range of postmenopausal women, including older adults, the official regulatory documents do not provide an explicit statement detailing age-related differences in the frequency or severity of common side effects. Dosing is consistent across the standard adult postmenopausal population.


Q: What is the definition of a 'contraindication' for Letrozole Specifar?

A contraindication is a medical term used to describe a condition or factor that absolutely forbids a certain medical treatment because of the harm it could cause the patient. For Letrozole, official contraindications are conditions like pregnancy, breastfeeding, or premenopausal endocrine status.


Q: How is the long-term safety of Letrozole Specifar described in regulatory documents?

Long-term safety is characterized by monitoring risks associated with the medicine's sustained reduction of estrogen levels. Regulatory data highlights that the long-term risks include a higher incidence of osteoporosis and bone fractures and the potential for cardiovascular events, necessitating ongoing monitoring of bone density and serum cholesterol.


Q: Does Letrozole Specifar affect sleep patterns?

Official safety data lists insomnia (difficulty sleeping) as an Uncommon adverse reaction. This classification means it is documented to occur in between 1 in 1,000 people and 1 in 100 people (ge 1/1000 to <1/100) who take the medicine, according to regulatory reporting.


Q: How does the TGA or Health Canada describe the use of Letrozole Specifar?

Official regulatory bodies like Health Canada and the Australian TGA describe the use of Letrozole as a treatment for hormone-receptor positive breast cancer in postmenopausal women. Their descriptions cover use in both the adjuvant setting (after initial treatment) and metastatic (advanced) disease, consistent with other global authorities.


Q: Do official sources list specific monitoring tests needed while on Letrozole Specifar?

Yes, official regulatory documents specifically recommend the regular monitoring of bone mineral density (BMD) and serum cholesterol levels during treatment. This monitoring is recommended due to the potential effects of the medicine's mechanism of action on bone and cardiovascular health.


Q: What are the key safety messages from regulatory bodies about Letrozole Specifar?

Key safety messages from regulatory bodies focus on the potential for osteoporosis/broken bones due to estrogen reduction, the requirement for effective contraception for women of childbearing potential, and the risk of dizziness/tiredness which may affect the ability to drive or operate machinery.


Q: How is the term 'adjuvant treatment' defined in relation to Letrozole Specifar?

The term adjuvant treatment in the context of Letrozole is defined as therapy given after primary treatment (such as surgery) for cancer. According to regulatory documents, the primary goal of adjuvant therapy is to lower the risk of the cancer returning in the future.


Q: Can I take multivitamins while using Letrozole Specifar?

Official guidance explicitly warns about certain herbal remedies (like St. John's Wort). Regarding other supplements, official guidance advises informing a healthcare professional about all vitamins, minerals, or supplements, as some may interact with the drug’s metabolism.


Q: Is Letrozole Specifar approved for use in early-stage breast cancer that has already spread to lymph nodes?

Clinical trial evidence included in regulatory documents supports the use of Letrozole in postmenopausal women with early breast cancer, regardless of whether the disease is lymph-node-positive or lymph-node-negative. This scope of use is based on the outcomes seen in large-scale studies.


Q: How is the general expectation of disease recurrence managed in the research evidence?

Regulatory documents manage patient expectations by reporting outcomes from large-scale studies, which use specific metrics. These metrics, such as Disease-Free Survival (DFS) and Distant Disease-Free Survival (DDFS), describe the patterns and time-to-event for disease recurrence or spread observed in different treatment groups.

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How should Letrozole Specifar be stored and disposed of?

Storage and Disposal of Letrozole Specifar

Official regulatory documentation outlines specific requirements for the storage and disposal of Letrozole Specifar tablets to ensure product integrity and public safety.

Required Storage Conditions

Condition Requirement
Temperature Store at a temperature not exceeding 30 C
Packaging Must be kept in the original package for protection from moisture
Safety Must be kept out of the sight and reach of children

Disposal Instructions

There are no special requirements for destroying the tablets. Unused, unwanted, or expired Letrozole Specifar must be disposed of according to local requirements and is prohibited from being thrown into household waste or flushed down the toilet. Following local guidelines ensures proper environmental handling.

Attention! Always consult to a doctor or pharmacist before using pills or medicines.

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