Tamoxifen

Brand names

• Alpha-Tamoxifen
• Apo-Tamox
• Dom-Tamoxifen
• Gen-Tamoxifen
• Nolvadex
• Nolvadex-D
• Novo-Tamoxifen
• PMS-Tamoxifen
• Tamofen
• Tamone

Usage

To treat breast cancer that is estrogen-receptor positive.

How it works

Tamoxifen blocks the effects of the hormone estrogen on certain organs in the body. Because the growth of some types of breast cancer is stimulated by estrogen, tamoxifen interferes with the growth of such tumors.

Side effects

Serious

Endometrial cancer (menstrual irregularities, abnormal nonmenstrual vaginal bleeding, changes in vaginal discharge, pelvic pain or pressure); deep vein thrombosis and pulmonary embolism (pain or swelling in legs, shortness of breath, sudden chest pain, coughing up blood); cataracts; new breast lumps; confusion, weakness, or drowsiness; yellowish tinge to eyes or skin.

Common

Hot flashes, weight gain, nausea, vomiting.

Less common

Bone pain, headache, visual disturbances, skin dryness or rash, changes in menstrual period, vaginal discharge, itching in genital area of women, depression, impotence or decreased sexual interest in men. Other side effects include high blood calcium levels and liver dysfunction; such problems can be detected by your doctor.

Possible interactions

Other medicaments:

The following medicaments may decrease the effects of tamoxifen:

• estrogens.
• oral contraceptives (those that contain estrogens).

Tamoxifen taken concurrently with:



• allopurinol (Zyloprim) may worsen allopurinol toxicity to the liver.
• clopidogrel (Plavix) may result in higher than expected tamoxifen levels; no reports of adverse effects from this reaction have been made, but caution is advised.
• cyclophosphamide (Cytoxan) may increase blood clot (thromboembolism) risk.
• cyclosporine (Sandimmune) may increase cyclosporine levels and cause toxicity.
• medicines that inhibit CYP2C9 (such as fluconazole, fluvastatin and zafirlukast) may lead to increased tamoxifen levels.
• methotrexate (Mexate, Rheumatrex) may increase blood clot (thromboembolism) risk.
• mitomycin will cause increased risk of hemolytic uremic syndrome.
• pneumococcal and perhaps other vaccines will blunt the vaccine's immune response.
• ritonavir (Norvir) and perhaps other protease inhibitors may lead to toxicity.
• warfarin (Coumadin) presents an increased risk of bleeding; increased frequency of INR (prothrombin time or protime) testing is needed.

Herbal medicines or minerals:

Some patients use Echinacea to attempt to boost their immune systems. Unfortunately, use of Echinacea is not recommended in people with damaged immune systems. This herb may also actually weaken any immune system if it is used too often or for too long a time.

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