Arimidex (anastrozole) represents a significant advancement in hormonal therapy for postmenopausal women with hormone receptor-positive early and advanced breast cancer. As a third-generation aromatase inhibitor, it offers targeted estrogen suppression through a well-tolerated oral formulation. This medication has demonstrated superior efficacy compared to traditional anti-estrogen therapies in multiple clinical trials, establishing itself as a cornerstone in modern oncology practice. Its mechanism of action provides a more specific approach to estrogen deprivation without affecting other steroid hormones.

Features

• Contains 1 mg of anastrozole per tablet
• Non-steroidal aromatase inhibitor class medication
• Oral administration with once-daily dosing
• Bioavailability of approximately 80% when taken orally
• Mean elimination half-life of 50 hours in postmenopausal women
• Hepatic metabolism primarily via CYP3A4 and CYP3A5
• Excretion primarily through hepatic clearance with minimal renal elimination
• White, biconvex tablets with engraved dosing information

Benefits

• Significantly reduces recurrence risk in early breast cancer when used as adjuvant therapy
• Demonstrates superior disease-free survival rates compared to tamoxifen
• Provides effective estrogen suppression without progestogenic, androgenic, or estrogenic effects
• Lower incidence of thromboembolic events and endometrial cancer compared to tamoxifen
• Maintains bone mineral density better than other aromatase inhibitors in some patient populations
• Improves overall survival in advanced hormone receptor-positive breast cancer

Common use

Arimidex is primarily indicated for the treatment of hormone receptor-positive early breast cancer in postmenopausal women, typically administered as adjuvant therapy following primary treatment. It is also approved for first-line treatment of hormone receptor-positive advanced breast cancer in postmenopausal women and for treatment of advanced breast cancer that has progressed following tamoxifen therapy. The medication is used in extended adjuvant settings for women who have completed standard tamoxifen therapy, providing continued protection against recurrence. Clinical practice also includes its use in neoadjuvant settings to reduce tumor size before surgery in eligible patients.

Dosage and direction

The recommended dosage of Arimidex is one 1 mg tablet taken orally once daily, with or without food. Patients should take the medication at approximately the same time each day to maintain consistent plasma concentrations. Treatment duration for adjuvant therapy typically continues for five years, though extended therapy may be considered based on individual risk assessment. For advanced breast cancer, treatment continues until disease progression or unacceptable toxicity occurs. No dosage adjustment is necessary for elderly patients or those with mild to moderate hepatic impairment. Patients with severe hepatic impairment should use caution, though specific dosage recommendations have not been established.

Precautions

Patients should undergo comprehensive bone mineral density assessment before initiating therapy and at regular intervals during treatment due to the increased risk of osteoporosis. Regular monitoring of lipid profiles is recommended, as aromatase inhibitors may affect cholesterol metabolism. Hepatic function should be assessed periodically, particularly in patients with pre-existing liver conditions. Patients with pre-existing ischemic heart disease require careful cardiovascular monitoring throughout treatment. Caution is advised when prescribing to patients with known hypersensitivity to anastrozole or any excipients in the formulation. The medication should not be used in premenopausal women, as it does not effectively suppress estrogen in the presence of functioning ovaries.

Contraindications

Arimidex is contraindicated in premenopausal women, as it may not effectively suppress estrogen production in patients with functioning ovaries. The medication is contraindicated in patients with known hypersensitivity to anastrozole or any components of the tablet formulation. It should not be used during pregnancy (Pregnancy Category D) or breastfeeding, as animal studies have shown potential fetal harm. Concomitant use with estrogen-containing therapies is contraindicated, as these agents would counteract the therapeutic effect of anastrozole. The medication is contraindicated in patients with severe hepatic impairment where safety has not been established.

Possible side effect

Common adverse reactions include hot flashes (35%), asthenia (16%), arthritis (17%), arthralgia (15%), pain (14%), hypertension (13%), depression (13%), nausea (11%), headache (9%), and bone pain (7%). Less frequent but clinically significant side effects may include osteoporosis with increased fracture risk (10%), carpal tunnel syndrome (2%), vaginal dryness (2%), and elevated cholesterol levels (9%). Rare but serious adverse events include ischemic cardiovascular events (2%), venous thromboembolism (1%), and clinical fractures (4%). Most side effects are mild to moderate in severity and often diminish with continued therapy.

Drug interaction

Arimidex demonstrates minimal interaction with other medications due to its metabolism primarily through conjugation rather than cytochrome P450 pathways. However, potent CYP3A4 inducers such as rifampicin may decrease anastrozole concentrations by approximately 27%. Tamoxifen co-administration reduces anastrozole plasma concentrations by 27% and should be avoided. Estrogen-containing therapies counteract the therapeutic effect of anastrozole and are contraindicated. No clinically significant interactions have been observed with warfarin, though monitoring is recommended when initiating combination therapy. The medication does not interact significantly with common supportive medications used in cancer care.

Missed dose

If a dose is missed, patients should take it as soon as remembered unless it is nearly time for the next scheduled dose. In that case, the missed dose should be skipped, and the regular dosing schedule resumed. Patients should not double the dose to make up for a missed administration. Consistent daily dosing is important for maintaining therapeutic estrogen suppression, but occasional missed doses are unlikely to significantly impact overall treatment efficacy. Healthcare providers should educate patients about the importance of adherence and develop strategies to minimize missed doses.

Overdose

There is limited clinical experience with Arimidex overdose. Single doses up to 60 mg have been administered without serious adverse effects. In case of suspected overdose, supportive care should be provided with attention to possible estrogen withdrawal symptoms. Gastric lavage may be considered if ingestion occurred within a short time frame. Since anastrozole is not dialyzable due to high protein binding, dialysis is not expected to enhance elimination. Monitoring should include assessment of vital signs and symptomatic treatment of any adverse effects. No specific antidote exists for anastrozole overdose.

Storage

Store Arimidex tablets at room temperature between 15°C and 30°C (59°F and 86°F) in their original container. Protect from light and moisture, and keep the bottle tightly closed. Do not store in bathroom cabinets where humidity levels may fluctuate. Keep out of reach of children and pets. Do not use tablets that appear discolored or show signs of deterioration. Proper storage ensures stability throughout the expiration period printed on the packaging.

Disclaimer

This information is provided for educational purposes only and does not constitute medical advice. Treatment decisions should be made in consultation with a qualified healthcare professional who can assess individual patient circumstances. The prescribing physician should be familiar with the complete prescribing information and latest clinical guidelines. Patients should report any adverse effects to their healthcare provider and adhere to recommended monitoring schedules throughout treatment.

Reviews

Clinical studies demonstrate that Arimidex significantly improves disease-free survival compared to tamoxifen, with a 26% reduction in recurrence risk according to the ATAC trial. The BIG 1-98 trial confirmed these findings, showing particular benefit in node-positive patients. Patient-reported outcomes indicate generally good tolerability, though musculoskeletal symptoms remain a common reason for discontinuation. Long-term follow-up data confirm maintained efficacy with appropriate management of side effects. Many oncologists consider anastrozole the preferred adjuvant treatment for appropriate postmenopausal patients based on its established efficacy profile and manageable safety concerns.