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Can someone help me understand this about Tarceva???


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Maybe this is why Brian is having such a rough few days!!

Look what I found on line:

DRUG INTERACTIONS: CYP3A4 is an enzyme in the liver that breaks-down and helps to eliminate erlotinib from the body. Drugs that inhibit CYP3A4 can result in high levels of erlotinib in the body, and the high levels can result in toxicity from erlotinib. Such drugs include atazanavir (Reyataz), clarithromycin (Biaxin), indinavir (Crixivan), itraconazole (Sporanox), ketoconazole (Nizoral), nefazodone (Serzone), nelfinavir (Viracept), ritonavir (Norvir), saquinavir (Invirase; Fortovase), telithromycin (Ketek), and voriconazole (VFEND). In patients receiving these drugs, a lower dose of erlotinib may be needed to prevent toxicity.

Brian was given Tarceva (erlotinib) to start on Thursday. At the same time he was given Biaxin to treat the FUO.

I don't think that 4 doses of Tarceva could cause toxicity, but it concerns me that our onc would prescribe these conflicting drugs............

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I could see where this could be easily not known by the doctor. I would think it would be really hard to know all the drugs that could be harmful if taken together, however, if the Biaxin was a drug prescribed and picked up by the same pharmacy, the pharamacists should have picked up on it when he/she filled the prescription.

If I were you, I would call the doctor tomorrow morning and just tell them that you see that there is a warning against taking those two drugs together and see what they say.



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Tarceva is a relatively new medication. Many Physicians have yet to prescribe this drug for their patients, and may not be fully aware of all the drug interations. I make certain to tell all of my medical providers that I am taking Tarceva and that it reacts to CYP3A4 Inducers/Inhibitors.

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The pharmacist may be helpful in answering these questions for you. We have a 24hour pharmacy , do you? Give the pharmacist a call. I know ours is very helpful. Sure hope you get some answers tomorrow from your doctor and your pharmacist. Extra prayers coming your way...

Love and Prayers,


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