When they originally did the dose-finding study on Zytiga, they used the 1000 mg/day fasting dose. So that's the dose they have the most info on. Above that optimum dose, you're getting more toxicity and not much treatment, so you should not exceed that. More is not better. Because absorption varies with food intake, and the amount absorbed will vary from man to man, they left 1000 mg/day fasting as the standard dose.
But the stuff is expensive, and many men would like to take smaller doses if they can get the same benefit. There have been 3 small studies of low dose Zytiga with food:
With a low fat meal (n=36):ascopubs.org/doi/10.1200/JCO.2017.76.4381
With a high-fat meal (n=21):/meetinglibrary.asco.org/record/98068/abstract
Comparing low fat (n=6) and high-fat (n=18):/accp1.onlinelibrary.wiley.com/doi/abs/10.1002/jcph.564
All of the studies were very small, so you should only reduce the dose under advisement and close observation by your oncologist.
Allen - not an MD
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