Newbie question here. I know with the prescription Rapamune (Pfizer) they used a coating on the pill to help it make its way past the stomach so it can be absorbed.
I think I read that the Zydus and others from overseas do not have the coating, and that people are using extra virgin olive oil, fish, or other fatty meals to help absorption or grapefruit juice if you want to shoot the amount up 7x. I’m assuming if you don’t use some way to help the Zydus be absorbed you’ll effectively get zero.
My question is if the target dose is 6-8mg of Rapamune (Pfizer) with the coating, what is the equivalent amount with Zydus & a fatty meal?
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The short answer is we don’t know the difference in terms of bioavailability between Pfizer Rapamune, and generics like Zydus sirolimus, Biocon sirolimus, etc… There have been no comparison studies between the two that I’m aware of. But I think the two are reasonably close in terms of bioavailability as these drugs are used mostly for organ transplant patients and if there was a dramatic difference between the two drugs you’d hear about it from doctors and patients complaining about organ rejection issues.
Pfizer rapamune uses an in-licensed technology called “nanocrystals” for their rapamune. You can read more about this here: Rapamycin and NanoCrystal Formulations Pfizer / Elan Pharma who designed the nanocrystal technology claims a 30% improvement over lipid based solutions… but that is not a comparison to the generic sirolimus tablets.
Zydus seems to use some sort of coating that protects the rapamycin as it travels through your stomach. When I’ve crushed Zydus sirolimus for use in rapamycin toothpaste you see that there is some sort of film coating that is left over when you crush and dissolve the tablets. I think Biocon uses something similar in their generic tablets.
There is no evidence that the bioavailability of the generic versions of rapamycin (Zydus, Biocon, etc.) are significantly different than Rapamune.
People do use fatty meals, and grapefruit juice to increase bioavailability - and those strategies will likely work for Rapamune as well as the generic versions of rapamycin. For more on this, see this thread: Improve Bioavailability of Rapamycin (2)
Another thing to keep in mind that there can be significant differences in the blood levels that people experience after taking a fixed dose of rapamycin. Everyone is different, so a dose of 6mg may have a very different result in terms of blood sirolimus levels for you vs. another person of similar weight.
There are also other foods / compounds that you may injest that also impact bioavailability; learn more here: Rapamycin Interactions with Other Food, Drinks, Supplements and Drugs
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Great points. I’d love to see a comparative study, and agree with your point that if there was a big difference we’d hear about it in transplant forums.