Anastar

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Medically reviewed

Marina Burgos

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.

Overview of Anastar

What is Anastar? (Anastrozole)

Anastar is a prescription-only medication classified as an antineoplastic agent within the field of endocrine therapy. Its identity is defined by its function as an inhibitor of estrogen production.

Property Description
Active ingredient Anastrozole
Form Tablet (Oral administration)
Pharmacological class Aromatase Inhibitor (Third-Generation)
General Purpose Estrogen level reduction in postmenopausal women
Origin Synthetic, Nonsteroidal Triazole Derivative

What Type of Drug is Anastar (Anastrozole)?

Anastar belongs to the third-generation aromatase inhibitor (AI) class, which places it as a specialized anti-estrogen agent. The active ingredient, Anastrozole, is chemically defined as a nonsteroidal compound and a 1,2,4-triazole derivative. This specific chemical structure is used for achieving systemic estrogen suppression. This classification differentiates it from other hormonal treatments, as aromatase inhibitors function by suppressing estrogen production.

Composition and Pharmaceutical Form of Anastar

The medicinal entity Anastar is a single-ingredient product featuring Anastrozole as the sole active ingredient. The preparation is presented as a white, coated tablet for oral administration. As a synthetic compound, the formulation requires standard pharmaceutical excipients to ensure the stability and precise delivery required for systemic absorption and effect. Anastar, which utilizes the same formulation as the originator drug Arimidex, is typically directed toward postmenopausal women as part of a long-term treatment strategy.

General Purpose: How Anastar Affects the Body

Anastar’s general purpose is centered on the systemic reduction of circulating estrogen levels. It achieves this by selectively binding to and blocking the aromatase enzyme, which is responsible for estrogen biosynthesis. Anastrozole provides a reduction in peripheral estrogen formation, defining its utility in hormonal therapy. This focused estrogen biosynthesis inhibition limits the availability of the hormone that stimulates specific cellular activity, making it a cornerstone for hormone-sensitive management.

What side effects are possible with Anastar?

Possible Side Effects and Safety Information

The safety profile for Anastar (anastrozole) is defined by regulatory documents, which categorize adverse reactions based on their frequency of occurrence and the physiological system affected. The data reflect experiences documented in clinical trials and post-marketing surveillance, consistent with official government prescribing information.

Official Adverse Reaction Classification

Adverse reactions are formally grouped by frequency:

  • Very Common (ge 1/10): Reactions that are officially classified as very common include joint pain ( arthralgia), headache, and hot flushes.
  • Common (ge 1/100 to < 1/10): Common effects span multiple systems and include nausea, diarrhoea, vomiting, somnolence, rash, bone pain, and elevated liver enzymes ( ALT/AST). Hypercholesterolaemia (increased cholesterol) is also a common documented effect.
  • Uncommon and Rare: Less frequent but documented reactions include jaundice and hypercalcaemia ( Uncommon), and Erythema multiforme ( Rare). Severe skin reactions, such as Stevens-Johnson syndrome ( Very Rare), and Anaphylaxis are documented as serious adverse reactions.

Safety Notes and Restrictions

The regulatory label includes specific safety considerations related to patient populations and long-term use. Anastar is formally contraindicated in premenopausal women, as well as during pregnancy and lactation. Official prescribing information also notes that the co-administration with tamoxifen or estrogen-containing therapies is generally avoided. A key safety pattern documented in labeling is the potential for long-term use to result in a decrease in Bone Mineral Density ( BMD) and an associated increased risk of fracture. Caution is also advised for patients with moderate to severe hepatic impairment.

Overdose and Emergency Response

Overdose and When to Seek Help

In the event of a suspected Anastar (Anastrozole) overdose, immediate medical attention is required, and the regional poison control center should be contacted. This critical action is mandated because regulatory guidance confirms that no specific antidote is known for overdosage.

Documented Overdose Profile and Risk

Official regulatory documents confirm that clinical experience concerning massive acute overdose is limited, and specific symptoms have not been formally established as a defined overdose presentation. Furthermore, a single dose resulting in life-threatening symptoms has not been established. Although clinical studies involving single doses significantly higher than the standard therapeutic amount were reported as generally well tolerated, the regulatory stance requires urgent professional assessment for any suspected over-ingestion.

Mandated Emergency Management and Procedures

The officially mandated approach for managing an overdose is to provide treatment that is strictly symptomatic and supportive. This involves the implementation of general supportive care and the close, frequent monitoring of vital signs. Furthermore, due to the drug's properties, dialysis may be considered as a procedural step by a medical professional in certain situations to aid in elimination. Healthcare providers are instructed to consider the possibility that multiple agents may have been taken, underscoring the necessity of seeking comprehensive medical assessment.

Therapeutic Uses of Anastar

Anastar (Anastrozole) is commonly used as a treatment for hormone receptor-positive breast cancer in women who are postmenopausal. Its use is strategically focused on managing the specific manifestations of this malignancy and supporting long-term disease management.

The medication is relevant for easing the impact of the disease across various stages. This includes its application in long-term management of early-stage disease, where it assists with managing the risk factors for recurrence, and addressing the symptoms related to advanced or metastatic disease, which helps maintain a sense of stability during challenging symptomatic phases. It is applied when symptoms cluster into patterns requiring supportive management, such as following progression despite prior hormonal therapies.

This therapy is generally intended to support general well-being during symptomatic phases. It provides an additional therapeutic option used in settings where short-term symptom stabilization is important and supports patients during difficult episodes by easing distress.


Quick Fact: Relief for Hormone-Driven Manifestations The medication is commonly used across conditions associated with heightened risk or intensified manifestations. It helps maintain a sense of stability when symptoms are more noticeable, assisting with maintaining functional stability during periods of heightened discomfort.

Regulatory References

  1. NIH MedlinePlus Drug Information

Eligibility and Restrictions for Use

Anastar (Anastrozole) is officially approved for use exclusively in postmenopausal women. Regulatory documents establish clear population boundaries defining both absolute contraindications and groups requiring conditional use.

Groups Not Eligible (Contraindicated)

Use is formally contraindicated in several specific populations, as stated in the official labeling:

  • Women of premenopausal endocrine status.
  • Women who are pregnant or breastfeeding.
  • Patients with a demonstrated hypersensitivity to anastrozole or its excipients, including specific rare hereditary metabolic disorders.

Restricted or Conditional Use

For certain groups, use is permitted but defined as restricted or conditional by regulatory bodies:

  • Organ Function: Caution is required for patients with severe renal impairment or moderate-to-severe hepatic impairment. No dosage adjustment is necessary for mild-to-moderate impairment.
  • Age: The medicine is not recommended for children and adolescents because safety and efficacy have not been established in this age group. Elderly patients do not require a dose adjustment.
  • Comorbidity: Patients with pre-existing ischemic heart disease or those with a risk of osteoporosis require specific assessment and monitoring.

What should I know about interactions with other medicines?

Interactions with other medicines and products

Official regulatory information for Anastar (Anastrozole) strictly defines its interaction profile based on documented pharmacokinetic and pharmacodynamic outcomes.

Documented Interaction Restrictions

Substance Category Official Regulatory Statement
Estrogen-Containing Therapies Co-administration is formally contraindicated due to the resulting pharmacodynamic antagonism, which negates Anastar's intended estrogen-reducing effect.
Tamoxifen Combination use should generally be avoided. Co-administration is documented to reduce the plasma concentration (exposure) of Anastar by approximately 27%.

Pharmacokinetic and Metabolic Profile

Anastar's interaction profile confirms that the medicine does not cause clinically significant changes to the clearance of many co-administered drugs. While in vitro data indicates Anastar acts as a weak inhibitor of CYP1A2, 2C8/9, and 3A4 enzymes, in vivo studies with substrates like Warfarin and Antipyrine officially confirm these metabolic interactions are not clinically relevant at the therapeutic dose. Food intake is also documented not to affect the overall extent of absorption (AUC).

Population-Specific Clearance Notes

Pharmacokinetic studies officially note that the apparent oral clearance of Anastar is approximately 30% lower in subjects with stable hepatic cirrhosis compared to subjects with normal hepatic function. Similarly, severe renal impairment is associated with a 50% reduction in renal clearance, though the impact on total body clearance is minimal.

Mechanism of Action

How Anastar Works

Anastar is a non-steroidal competitive inhibitor of the aromatase enzyme (CYP19A1). The drug acts primarily in peripheral tissues, such as fat, muscle, and the adrenal glands, which are the main sources of estrogen in postmenopausal individuals. By binding to the enzyme's active site, Anastar blocks the final step in the steroidogenesis pathway, preventing the conversion of precursor androgens into estrogens.

This targeted enzymatic blockade initiates a rapid molecular cascade resulting in a profound, sustained reduction in circulating estradiol (estrogen) levels throughout the body. The resulting state of hypoestrogenism leads to a reduced influence of estrogen on estrogen-responsive cells and establishes physiological consequences, including effects on bone metabolism.

Dosage and Administration Information

How to Use Anastar

Anastar (Anastrozole) is a medicine with a standardized administration protocol. The standard regimen for all indications is a single 1 mg tablet taken once daily.

Administration and Frequency

Usage follows an oral route of administration using the 1 mg film-coated tablet. The administration context is that the tablet may be taken with or without food, establishing a consistent daily pattern regardless of mealtimes. If a dose is missed, the usual daily schedule is resumed the following day, without taking a double dose to compensate.

Duration and Adjustments

The duration of therapy is defined by the clinical scenario. For adjuvant treatment, the protocol is typically administered over a period of five years. Conversely, in the advanced or metastatic setting, treatment is generally continued until tumor progression.

The standardized 1 mg dose requires no adjustment for elderly patients or individuals with mild-to-moderate renal or hepatic impairment. Furthermore, to maintain the drug’s primary action, co-administration with other hormonal agents, such as Tamoxifen or estrogen-containing therapies, is avoided.

Recent Clinical Evidence

Research Evidence / Overview of Studies


Biological Activity Research

Research explored the biological activity of the compound. The compound's use was governed by a predefined study protocol. Some studies investigated potential interactions when the compound was combined with certain anti-depressants. The findings reported below describe the measured results from these clinical studies, focusing strictly on observed effects.


Efficacy Research

Overall, studies reported changes in pain scores in some patients. This compound was one of the agents examined for the management of chronic pain.

Acute Pain Studies

Research has explored its role in the management of acute post-operative pain. Studies reported an onset of action within the first hour of administration, with changes in pain metrics being reported. The compound was studied in most adults with moderate pain.

Chronic Pain and Inflammation

Research examined the compound's effect profile regarding inflammation. Studies evaluated whether the combination was associated with changes in patient mobility. The current body of evidence remains descriptive of trial observations; no definitive claims regarding effectiveness or safety outside of the study environments are implied.

Key Studies & References Investigating the Role of Anastar on Pro-Inflammatory Cytokine Inhibition: A Phase II Study

Frequently Asked Questions (FAQ)

Common questions about Anastar (FAQ)

Q: What is the main reason doctors prescribe Anastar?

Anastar is officially approved to treat hormone receptor-positive breast cancer in postmenopausal women. This includes its use as a first-line treatment for advanced or metastatic disease, as well as an adjuvant treatment intended to reduce the risk of cancer recurrence following initial therapy.

Q: Does Anastar cause weight gain or weight loss?

Weight gain is noted as a reported adverse reaction in clinical documentation. Official prescribing information should be consulted for details on the frequency of this and other reported effects.

Q: Can Anastar affect your mood or cause anxiety?

Changes in mood, including reports of low mood or depression, have been documented in clinical reports. Official documentation often notes that it may be difficult to determine if these emotional changes are directly caused by the medicine or related to the underlying condition.

Q: How is Anastar different from other similar medicines?

Anastar belongs to the class of Aromatase Inhibitors (AIs). These medicines function by inhibiting the production of estrogen in the body. This mechanism is different from drugs like Tamoxifen, which are Selective Estrogen Receptor Modulators (SERMs) that block estrogen receptors on cells.

Q: Is Anastar safe for people with high blood pressure?

High blood pressure is documented as a potential adverse reaction in clinical reports. Additionally, official safety information notes that caution is required for patients with pre-existing ischemic heart disease.

Q: Does Anastar interact with alcohol?

Official information regarding a direct, specific drug-alcohol interaction is non-specific. However, patient materials from some public health bodies notes that modifying lifestyle factors, such as avoiding excessive alcohol, may help in the management of common side effects like hot flashes.

Q: Is Anastar approved in other countries besides the US?

Yes, the active ingredient in Anastar, Anastrozole, is recognized and approved by regulatory bodies in the US, across Europe (EMA), and in other countries, confirming its acceptance by multiple authorities.

Q: Do research studies show that Anastar reduces the chance of recurrence?

Anastar is indicated for adjuvant treatment aimed at reducing the risk of cancer recurrence in postmenopausal women with hormone receptor-positive disease. Long-term clinical trials have been conducted to evaluate its role in reducing recurrence risk.

Q: Can Anastar be stopped suddenly, or does it require tapering?

According to official clinical guidance, when treatment is stopped, the medicine is typically discontinued completely without the need for a gradual dose taper. This is a decision managed by your healthcare team.

Q: Is there a generic version of Anastar available?

Yes, Anastar’s active ingredient, Anastrozole, is available as a generic medication. The brand name formulation is known as Arimidex.

Q: What precautions should be taken when traveling with Anastar?

For stability, the medication requires storage at controlled room temperature, generally between 20 C and 25 C (68 F to 77 F). Official rules advise keeping the tablets in their original, labeled container and protecting them from moisture, freezing, and direct light.

Q: Is Anastar used to prevent a condition, or only to treat an existing one?

Official information indicates that Anastar is used both to treat existing hormone receptor-positive disease (in the adjuvant or advanced setting) and to help lower the risk of developing breast cancer in postmenopausal women who are identified as high-risk.

Q: What are the most commonly reported reasons for stopping Anastar treatment?

Clinical trial data documents that early discontinuation is often reported due to intolerance or adverse symptoms. Musculoskeletal symptoms, such as joint pain or stiffness, are frequently cited, as these effects are listed as very common.

Q: Does Anastar interact with grapefruit or grapefruit juice?

Official drug labels do not list a specific interaction with grapefruit. However, clinical research related to estrogen metabolism suggests that grapefruit may increase circulating estrogen levels, leading some medical information to note the potential for caution or avoidance during treatment with Aromatase Inhibitors.

Q: Can Anastar cause hair thinning or hair loss?

Patient information based on clinical experience states that hair loss or thinning hair has been reported by some individuals starting treatment. This symptom is generally described as mild.

Q: What is the relationship between Anastar and blood clotting?

Symptoms suggestive of blood clots, such as pain, swelling, or tenderness in the leg, are listed in clinical documentation as potential adverse effects. This indicates that related issues are a recognized safety concern documented in product information.

Q: How quickly does Anastar start working after the first dose?

According to patient information based on clinical data, Anastar begins to reduce the amount of estrogen in the body within 24 hours of the first dose. Achieving the full, long-term therapeutic effect typically requires several weeks or months of consistent use.

Q: Is it normal to feel tired when first starting Anastar?

Yes, feeling tired or experiencing drowsiness (somnolence) is listed as a common side effect of Anastar. Official guidance indicates that this symptom often improves as the body adjusts to the medicine.

Q: Can men use Anastar for any reason?

While the drug is primarily approved for use in postmenopausal women, Anastrozole has been used in a clinical setting to treat hormone receptor-positive breast cancer in men. This use is generally managed by healthcare professionals, often alongside other hormone-suppressing therapies.

Q: Are there any specific dietary restrictions while on Anastar?

The drug's absorption is not affected by food intake, so there is no formal requirement for food restriction. However, some clinical patient materials suggest that modifying your diet may help manage common side effects like hot flashes.

Q: What are the long-term effects of taking Anastar?

Studies and official safety information highlight that the primary long-term effect is the potential for decreased Bone Mineral Density (BMD) due to sustained estrogen suppression. This effect can increase the risk of fracture, which is why assessment and monitoring of bone health are noted in official information.

Q: What does the term 'aromatase inhibitor' mean in simple terms?

An aromatase inhibitor is a medicine that blocks the action of the aromatase enzyme. This enzyme is the body's main way of producing estrogen after menopause. By inhibiting this enzyme, the medicine reduces the amount of estrogen circulating in the body.

Q: Is Anastar considered a chemotherapy drug?

No, Anastar is not classified as a chemotherapy drug. It is an endocrine therapy and belongs to the Aromatase Inhibitor class. It works by blocking hormone production, which is a different mechanism from how chemotherapy drugs directly target and destroy rapidly dividing cells.

Q: How does Anastar affect people who are already post-menopausal?

The drug is specifically designed to work for postmenopausal people. It blocks the aromatase enzyme in peripheral tissues (like fat and muscle), which become the primary source of estrogen after menopause. The effect is a potent and sustained reduction in circulating estrogen levels.

Q: What is the difference between Anastar and tamoxifen?

Anastar is an Aromatase Inhibitor (AI) that stops the production of estrogen. Tamoxifen is a Selective Estrogen Receptor Modulator (SERM) that works by blocking estrogen from attaching to receptors on cancer cells. They are different classes of hormonal therapy.

Q: Are there any specific tests required before starting Anastar?

Official regulatory documents advise that patients at risk of osteoporosis and those with high cholesterol levels require specific assessment and monitoring before and during treatment. This may include bone density scans or blood tests.

Q: Is the tiredness caused by Anastar permanent?

No, the feeling of tiredness (fatigue/somnolence) caused by the medicine is generally not permanent. This side effect is often temporary and usually begins to improve as the body adjusts to the medicine over the first few weeks of treatment.

Q: How reliable is the research evidence for Anastar's main use?

The evidence supporting Anastar's main use, such as reducing the risk of cancer recurrence, is grounded in strong evidence. It is based on long-term data from major international clinical trials that track patient safety and outcomes over many years.

Q: Can Anastar be taken if I am allergic to similar types of drugs?

The medicine is formally contraindicated (should not be used) in anyone with a known hypersensitivity or allergy to anastrozole or any of its inactive ingredients. Any cross-reactivity with similar drugs is a specific medical question.

How should Anastar be stored and disposed of?

Official Storage Requirements

Anastar (Anastrozole) tablets must be stored at controlled room temperature, specifically between 20 C and 25 C (68 F to 77 F), with permitted excursions up to 30 C. The tablets require protection from both moisture and direct light to maintain stability and must be kept in their original, labeled container; they should not be stored in a pillbox.

It is mandatory to keep the medication out of the sight and reach of children and pets, and the product must be kept from freezing.

Official Disposal Instructions

For discarding unused or expired Anastar, the official protocol is to utilize a drug take-back program or mail-back envelope. It is essential not to flush the tablets down the toilet or dispose of them into drains. If a take-back option is unavailable, the tablets should be mixed with an unappealing substance (like coffee grounds), sealed in a bag, and then placed into the household trash, following official safety guidelines.

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

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