Overview
11 DESCRIPTION Anastrozole tablets, USP for oral administration contain 1 mg of anastrozole, a non-steroidal aromatase inhibitor. It is chemically described as 1,3-Benzenediacetonitrile, a, a, a', a'-tetramethyl-5-(1H-1,2,4-triazol-1-ylmethyl). Its molecular formula is C 17 H 19 N 5 and its structural formula is: Anastrozole is an off-white powder with a molecular weight of 293.4.
Mechanism of Action
12 CLINICAL PHARMACOLOGY 12.1 Mechanism of Action The growth of many cancers of the breast is stimulated or maintained by estrogens. In postmenopausal women, estrogens are mainly derived from the action of the aromatase enzyme, which converts adrenal androgens (primarily androstenedione and testosterone) to estrone and estradiol. The suppression of estrogen biosynthesis in peripheral tissues and in the cancer tissue itself can therefore be achieved by specifically inhibiting the aromatase enzyme. Anastrozole is a selective non-steroidal aromatase inhibitor. It significantly lowers serum estradiol concentrations and has no detectable effect on formation of adrenal corticosteroids or aldosterone. 12.
Indications
- 1 INDICATIONS AND USAGE Anastrozole is an aromatase inhibitor indicated for: Adjuvant treatment of postmenopausal women with hormone receptor-positive early breast cancer ( 1.1 ) First-line treatment of postmenopausal women with hormone receptor-positive or hormone receptor unknown locally advanced or metastatic breast cancer ( 1.2 ) Treatment of advanced breast cancer in postmenopausal women with disease progression following tamoxifen therapy. Patients with ER-negative disease and patients who did not respond to previous tamoxifen therapy rarely responded to anastrozole ( 1.3 ) 1.
Common Doses
- 1 mg
Dosage
2 DOSAGE AND ADMINISTRATION One 1 mg tablet taken once daily ( 2.1 ) 2.1 Recommended Dose The dose of anastrozole tablet is one 1 mg tablet taken once a day. For patients with advanced breast cancer, anastrozole tablets should be continued until tumor progression. Anastrozole tablets can be taken with or without food. For adjuvant treatment of early breast cancer in postmenopausal women, the optimal duration of therapy is unknown. In the ATAC trial, anastrozole was administered for five years [see Clinical Studies ( 14.1 )].
Contraindications
- 4 CONTRAINDICATIONS Hypersensitivity Anastrozole is contraindicated in any patient who has shown a hypersensitivity reaction to the drug or to any of the excipients. Observed reactions include anaphylaxis, angioedema, and urticaria [see Adverse Reactions ( 6.2 )]. Patients with demonstrated hypersensitivity to anastrozole or any excipient ( 4 )
Side Effects
- 6 ADVERSE REACTIONS Serious adverse reactions with anastrozole occurring in less than 1 in 10,000 patients, are: 1) skin reactions such as lesions, ulcers, or blisters; 2) allergic reactions with swelling of the face, lips, tongue, and/or throat. This may cause difficulty in swallowing and/or breathing; and 3) changes in blood tests of the liver function, including inflammation of the liver with symptoms that may include a general feeling of not being well, with or without jaundice, liver pain or liver swelling [see Adverse Reactions ( 6.2 )].
Interactions
- 7 DRUG INTERACTIONS Tamoxifen: Do not use in combination with anastrozole. No additional benefit seen over tamoxifen monotherapy ( 7.1 , 14.1 ). Estrogen-containing products: Combination use may diminish activity of anastrozole ( 7.2 ). 7.1 Tamoxifen Co-administration of anastrozole and tamoxifen in breast cancer patients reduced anastrozole plasma concentration by 27%. However, the co-administration of anastrozole and tamoxifen did not affect the pharmacokinetics of tamoxifen or N-desmethyltamoxifen.