Anastelb (Anastrozole)

What Is Anastelb and What Is It Used For?

Anastelb belongs to a class of medicines known as aromatase inhibitors. The active substance, anastrozole, is a potent, selective, non-steroidal inhibitor of the enzyme aromatase (also known as cytochrome P450 19A1 or CYP19A1). This enzyme is responsible for converting androgens into estrogens in peripheral tissues such as adipose tissue, muscle, liver, and within breast tumour cells themselves.

In postmenopausal women, estrogen is no longer produced by the ovaries. Instead, the primary source of estrogen is the peripheral conversion of androgens (produced by the adrenal glands) into estrogens via the aromatase enzyme. By blocking this enzyme, anastrozole reduces circulating estradiol levels by approximately 80% within 24 hours of administration, with maximum suppression achieved within 7 days of once-daily dosing.

Approximately 70–80% of all breast cancers are hormone-receptor-positive, meaning they express estrogen receptors (ER+) and/or progesterone receptors (PR+). These tumours depend on estrogen to grow and proliferate. By dramatically lowering estrogen levels, Anastelb effectively starves these cancer cells of the hormonal signal they need to survive and multiply.

Approved Indications

Anastelb is primarily indicated for the treatment of hormone-receptor-positive breast cancer in postmenopausal women. Specific clinical settings where it may be prescribed include:

• Adjuvant therapy: Treatment given after primary breast cancer surgery to reduce the risk of cancer recurrence. The landmark ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial demonstrated that anastrozole significantly reduced disease recurrence compared to tamoxifen in postmenopausal women with early-stage breast cancer.
• First-line treatment of advanced or metastatic disease: Anastelb may be used as initial endocrine therapy for locally advanced or metastatic breast cancer in postmenopausal women with hormone-receptor-positive tumours.
• Second-line therapy: It may be used in women whose disease has progressed despite previous anti-estrogen therapy such as tamoxifen.

The efficacy of anastrozole in the adjuvant setting has been extensively documented. In the ATAC trial, which enrolled over 9,000 postmenopausal women, anastrozole demonstrated a statistically significant improvement in disease-free survival compared to tamoxifen at 5 years, 10 years, and even in extended follow-up beyond 10 years. These results established aromatase inhibitors as a standard of care for postmenopausal women with early-stage hormone-receptor-positive breast cancer.

What Should You Know Before Taking Anastelb?

Before starting Anastelb, it is essential that you have a thorough discussion with your healthcare provider about your medical history, current medications, and any pre-existing conditions. Aromatase inhibitors have a distinct side effect profile compared to other breast cancer therapies, and understanding the risks and benefits is crucial for informed treatment decisions.

Contraindications

Warnings and Precautions

Talk to your doctor or pharmacist before taking Anastelb if any of the following apply to you:

• Bone health concerns: If you have ever had osteoporosis or low bone mineral density, you may be at increased risk of fractures during treatment. Your doctor should evaluate your bone health before starting therapy and monitor it regularly throughout treatment. Preventive measures such as calcium and vitamin D supplementation, weight-bearing exercise, and bone-protective medications (bisphosphonates) may be recommended.
• Liver or kidney problems: While anastrozole is primarily metabolised by the liver, dose adjustments are generally not required for mild to moderate hepatic or renal impairment. However, your doctor should be informed of any liver or kidney conditions so that appropriate monitoring can be arranged.
• Cardiovascular risk factors: Some studies have suggested a slightly increased risk of cardiovascular events with aromatase inhibitors compared to tamoxifen. If you have existing heart disease, high blood pressure, high cholesterol, or diabetes, these conditions should be actively managed during treatment.
• Musculoskeletal symptoms: Joint pain, stiffness, and arthralgia are very common with aromatase inhibitors. These symptoms can sometimes be severe enough to consider switching therapy. Discuss pain management strategies with your doctor.

Pregnancy and Breastfeeding

Anastelb is strictly contraindicated during pregnancy and breastfeeding. Anastrozole belongs to the group of medicines that can cause serious developmental harm to an unborn child. If you become pregnant while taking Anastelb, stop the medication immediately and contact your doctor urgently. Women of childbearing potential should use effective contraception during treatment and for at least 2 weeks after the last dose.

It is not known whether anastrozole passes into breast milk. However, due to the potential for serious adverse effects in the nursing infant, breastfeeding must be discontinued before starting Anastelb therapy.

Driving and Operating Machinery

Anastelb is unlikely to affect your ability to drive or use machines. However, some patients may occasionally experience weakness, drowsiness, or fatigue while taking this medicine. If you are affected, you should not drive or operate machinery until the symptoms resolve. You are responsible for assessing whether you are fit to perform these activities.

Lactose Content

How Does Anastelb Interact with Other Drugs?

Drug interactions can significantly affect the efficacy and safety of Anastelb. It is essential to inform your doctor or pharmacist about all medicines you are currently taking, have recently taken, or might take, including over-the-counter medications, herbal remedies, and dietary supplements.

Major Interactions

The following medications must not be taken together with Anastelb:

Other Interactions to Discuss with Your Doctor

The following medications should be discussed with your prescribing physician when taken alongside Anastelb:

Anastrozole is metabolised primarily through N-dealkylation, hydroxylation, and glucuronidation. In vitro studies indicate that anastrozole does not inhibit CYP1A2, CYP2C9, CYP2D6, CYP2A6, or CYP3A4 at clinically relevant concentrations. This means the potential for drug interactions through these cytochrome P450 pathways is generally low. However, individual variation exists and your doctor should be informed of all medications you are taking.

What Is the Correct Dosage of Anastelb?

Always take Anastelb exactly as your doctor has told you. Check with your doctor or pharmacist if you are not sure. The dosage is straightforward and consistent across most clinical indications, but the duration of treatment can vary depending on your individual circumstances.

Adults (Postmenopausal Women)

For adjuvant therapy (after breast cancer surgery), the recommended duration of treatment is typically 5 years. Current clinical guidelines from major organisations such as the European Society for Medical Oncology (ESMO) and the American Society of Clinical Oncology (ASCO) support 5 years of aromatase inhibitor therapy as standard. In some high-risk patients, your oncologist may recommend extended endocrine therapy for up to 10 years, which may include sequential treatment with tamoxifen followed by an aromatase inhibitor, or an aromatase inhibitor for the full duration.

For advanced or metastatic breast cancer, Anastelb is continued for as long as it remains effective and the side effects are manageable. Your oncologist will regularly assess treatment response through clinical examinations, blood tests, and imaging studies.

Children and Adolescents

Anastelb is not indicated for use in children and adolescents. There is no relevant use of anastrozole in the paediatric population for the approved indications. Safety and efficacy have not been established in patients under 18 years of age.

Elderly Patients

No dose adjustment is required in elderly patients. The standard dose of 1 mg once daily applies regardless of age. However, elderly patients may be at increased risk of osteoporosis and fractures, and bone health should be monitored carefully throughout treatment.

Patients with Hepatic or Renal Impairment

No dose adjustment is necessary for patients with mild to moderate hepatic impairment or mild to moderate renal impairment. Anastrozole has not been studied in patients with severe hepatic or severe renal impairment, and caution is advised in these populations.

Missed Dose

Overdose

Stopping Treatment

Do not stop taking Anastelb unless your doctor tells you to. Discontinuing treatment prematurely can increase the risk of cancer recurrence. If you experience side effects that concern you, discuss them with your oncologist before making any changes to your treatment regimen. Your doctor may be able to recommend strategies to manage side effects while continuing therapy.

What Are the Side Effects of Anastelb?

Like all medicines, Anastelb can cause side effects, although not everybody gets them. The side effects listed below are categorised by frequency according to international pharmacovigilance conventions. Many of these effects are related to the reduction of estrogen in the body and are expected consequences of the drug's mechanism of action.

It is important to understand that the benefits of Anastelb in reducing breast cancer recurrence and improving survival typically outweigh the risks of side effects. However, you should always report any new or worsening symptoms to your healthcare team so they can be appropriately managed.

Additionally reported (frequency not determined): dry eyes, lichenoid skin rash (small red-purple itchy bumps), tendon inflammation (tendinitis), tendon rupture, and impaired memory.

Effects on Bone Health

Anastrozole reduces estrogen levels, which plays a crucial role in maintaining bone mineral density. This can lead to a reduction in bone strength and an increased risk of fractures, particularly of the spine, hip, and wrist. The ATAC trial demonstrated that women taking anastrozole had a higher rate of fractures compared to those taking tamoxifen (11% vs 7.7% at 68 months of follow-up).

Your doctor will manage these risks according to established clinical guidelines for bone health in postmenopausal women. This may include:

• Baseline and periodic bone density scans (DEXA scans)
• Calcium supplementation (1000–1200 mg daily)
• Vitamin D supplementation (800–1000 IU daily)
• Weight-bearing and resistance exercise
• Bisphosphonate therapy (e.g. zoledronic acid) if bone density is significantly low

Reporting Side Effects

It is important to report suspected side effects after the medicine has been authorised. This allows ongoing monitoring of the medicine's benefit-risk balance. You can report side effects to your national pharmacovigilance authority (such as the FDA MedWatch programme in the United States, the Yellow Card Scheme in the United Kingdom, or the EMA EudraVigilance system in the European Union).

How Should You Store Anastelb?

Proper storage of medication ensures its effectiveness and safety throughout the treatment period. Anastelb should be stored under the following conditions:

• Temperature: Store at room temperature. No special temperature requirements are specified, but avoid extreme heat or moisture.
• Packaging: Keep the tablets in the original blister packaging to protect them from light and moisture.
• Child safety: Store in a safe place where children cannot see or reach them. Anastelb can be harmful to children if accidentally ingested.
• Expiry date: Do not use Anastelb after the expiry date printed on the carton and blister pack (after "EXP"). The expiry date refers to the last day of the stated month.

Do not dispose of medicines via wastewater or household waste. Ask your pharmacist about how to dispose of medicines that are no longer needed. These measures help to protect the environment.

What Does Anastelb Contain?

Active Ingredient

Each film-coated tablet contains 1 mg of anastrozole.

Other Ingredients (Excipients)

The inactive ingredients serve various purposes in the manufacturing and delivery of the tablet:

Appearance and Pack Sizes

Anastelb 1 mg tablets are white, round, film-coated tablets imprinted with ‘A1’ on one side. They are available in blister packs containing 28, 30, 50, 90, 98, or 100 film-coated tablets. Perforated unit-dose blister packs (28×1, 30×1, 50×1, 90×1, 98×1, 100×1 tablets) may also be available. Not all pack sizes may be marketed in every country.