Drugs Not To Be Taken Along with Tamoxifen in Cancer of Breast

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Warning Features Of Cancer Breast

Tamoxifen, an agent prescribed to the breast cancer patients, usually of postmenopausal, post-surgery and post-chemotherapy status; as an adjuvant therapy. It has beneficial effect in preventing recurrence. But, it has been seen that recurrences do occur sometimes in some patients. Researchers forward some of the explanations for it; Viz-

1. Existence of cancer stem cell and non-responsiveness to chemotherapy: There are cancer stem cells which do not respond to the chemotherapeutic agents and propagate later on, after a period of quiescence. Abnormalities in Notch protein has been implicated for it. Manipulation of Notch pathway is being researched for this problem with some encouraging results.
2. Relapse after tamoxifen may be due to altered cytocrome P oxidase (CYP2D6) system of liver enzymes. Tamoxifen acts in cases of estrogen receptor positive breast cancers, after getting metabolized to its active form endoxifen. Sometimes, in some patients, the enzyme system may be defective, so that the conversion to the active form is hampered. So, the desired effect of tamoxifen is not seen.
3. Some drugs, which also depend on CYP enzyme system for metabolism, if taken along with tamoxifen may prevent it to be metabolized to its active form, endoxifen for optimal action. This group can be targeted comfortably.

Those are;

• Antidepressants like; paroxetine, fluoxetine, bupropion and duloxetine,
• Antipsychotics: thioridazine, perphenazine and pimozide.
• Drugs on heart: quinidine and ticlopidine,
• Anti-infectives; terfenadine and quinolone.
• Others; Cinacalcet.
• Cemetidine (Histamine2 receptor antagonist), a gastric acid lowering drug.
• Some antihistaminics (Histamine1 Inhibitors)

These drugs can easily be substituted by less interactive and less CYP enzyme system dependent drugs like;

• Antidepressants:venlafaxine, desvenlafaxine, reboxetine, escitalopram, and mirtazapine,
• Antipsychotics: thiothixene, clozapine, risperidone and quetiapine.
• Cardiac drugs: diltiazem.
• Anti-infective agents like; indinavir, saquinavir, nevirapine and efavirenz.
• Others; Gabapentin,
• Anti-histaminics like; chlorpheniramine, cetrizine, and loratadine.
• Gastric acid inhibitors like ranitidine.

A little vigil in prescribing medication along with tamoxifen may well prevent some post-surgery and post-chemotherapy breast cancer patients from recurrences; which always disturbs the psychology of patients leading to depression and gives worst nightmare to the clinicians.

Original Source: http://www.medscape.com/viewarticle/716747.

Interesting information;”Why fatty people suffer from cancers and particularly cancer breast” can be seen in "From Clinician's Bioscope"

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• Antidepressant blocks tamoxifen benefit: Study (healthzone.ca)
• Antidepressant interferes with breast-cancer drug (cbc.ca)
• Raloxifene, Tamoxifen Both Guard Against Breast Cancer (nlm.nih.gov)

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