if you take them before the time of the fast begins (which is what they were designed for, if you could take them during the fast they wouldnt need to be long-lasting), yes they are permitted.
some people say they work, i strongly tend towards doubting that.
I don’t see what the problem would be with timed release nutrition if taken before yom kippur. After all, when we eat seudah mafsekes, the food we eat takes several hours to digest. So what really is the difference?
Time-release capsules, caffiene suppasotories, what else will they think of??? I can say with certainty that none of the above are in the spirit of the vi-ee-nee-sem aspect of the day….The whole point is to be uncomfortable and be inspired to do true tshuvah!!
If people are saying you shouldn’t take a capsule because it takes away from “Ve’inisem”, then most of the sneakers worn today should have the same problem.
Many are much MORE comfortable than every day dress shoes.