Advanced Prostate Cancer
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Xtandi and Zytiga Given Together

For those of you who are/were on Zytiga and Xtandi at the same time, I have a question. Were the doses and/or frequency adjusted to comply with the different metabolism rates of the two drugs when given together or were you treated with the standard doses of each drug? My Oncologist told me that he could not prescribe both drugs at the same time because they interact adversely because of their metabolism rates. I believe he said that the blood serum level of one goes up and one goes down. I do not remember which one went up and which one went down.

From the Full Prescribing Information under Drug Interactions for Xtandi and Zytiga is the following information.

From the Full Prescribing Information for Xtandi - Drug Interactions:

Avoid CYP3A4, CYP2C9 and CYP2C19 substrates with a narrow therapeutic index, as XTANDI may decrease the plasma exposures of these drugs.

From the Full Prescribing Information for Zytiga - Drug Interactions:

CYP3A4 Inducers: Avoid concomitant strong CYP3A4 inducers during ZYTIGA treatment. If a strong CYP3A4 inducer must be co-administered, increase the ZYTIGA dosing frequency.

CYP3A4 is also known as Cytochrome P450 3A4.

Richard

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I was on full dose of both after zytiga failed at 18 months , I added full dose xtandi to full dose zytiga and rode it for30 months. I did xtandi just before bed , and zytiga in morn

Dan

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Thanks Dan. I did Xtandi for almost 2.5 years and it started to fail. Switched to Zytiga 6 months ago and it is failing. I will show your reply to my Oncologist on 2/15 and see if he will put me on both for a while. If not, it's docetaxel. The problem with docetaxel is I already have grade 3 peripheral neuropathy (reasons unknown) and it is possible that chemotherapy will make it much worse.

Richard

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I used ice packs on bottoms of feet, and soaked fingers in ice water trying to prevent Nueropathy, It was mostly successful, there is actually a lot of post with information on this site on Nueropathy. When I did the combo xtandi zytiga, I had never done xtandi, Have you asked abouth increasing absorption of zytiga with food, Maybe ask the MO that question.

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I'm being told to take things 1 at a time, to get the longest ride, & that the evidence isn't there yet from a completed clinical trial to show a survival advantage from combining. That's what I'm being told, anyway. Did your MO say there was research showing a benefit from taking the combo?

I got interested in taking Zytiga with food late in the almost 3 years I was on it, when my PSA began to rise. My MO tried to scare me off that by explaining that there was 5 times as much danger of liver damage. Then I spoke with another MO who thought I should try it. I compromised by decreasing the time between Zytiga & food in half-hour intervals & watching the safety test numbers stay good. But when I was ready to go from 1/2 hour to simultaneous is when we had to conclude that Zytiga has failed. Of course I wondered whether it would have worked longer if I'd tried simultaneous Zytiga & food sooner.

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I did zytiga first, then added xtandi to it after 18 months when zytiga alone strted to fail, after the combo started to fail I started eating with the zytiga and got more time. I like your idea of getting the longest ride. I sometimes think my long survival may be due to the many drugs I got a response from before xtandi and zytiga , such as time on ketoconazole, and estradiol. After developing resistance to these drugs I still got a response from zytiga and xtandi.

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I was told not to take with food. So I wait till 2 or 3 AM to take it.

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Keep us posted on what happens please. When I added xtandi to the zytiga,I had never done the xtandi , and the combo worked, at this point I want to rechallenge with xtandi, and they tell me it will not work. When I am out of options I will try it anyway with the blessing of my local MO.

Best wishes

Dan

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Will do

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Remember to put fingertips on ice cubes so to not increase neuropathy. I did that on my first infusion and don't have in my fingertips. Didn't do that on feet so I have neuropathy there. Hope that helps.

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RLSHARP/Richard, I’m in a clinical trial at Kaiser right now- one random Wing takes Xtandi and Lupron: the other Wing takes Xtandi, Lupron, Zytiga and pretnizone. I’m in the Xtandi and Lupron Wing. The two legs are being compared for effective ness.

You may want to get a second opinion.

Art

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Do you know how long it will be until the results are available?

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Please keep us posted on what happens. I am on Xtandi, Zytiga, prednisone, Lupron right now. Also interested in finding out if that combination hurts my liver or ????. Probably will take long to find out . :-(

Thanks afab.

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Will do.

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I don’t have a clue. I’m anxious to know

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