I have no idea about time released. I think if you hit any amount at 100mg or above at one time you'll get the flush. But it does pass quickly. I wouldn't worry about that too much. Just dont' go more than or much more than 250 mg/day. You may find it in your protein mix and other places so if you do a supp, you may be adding to your daily total as well.
Niacin and niacinimide are also found in:
beef liver, brewer's yeast, broccoli, carrots, cheese, corn flour,dandelion greens, dates, eggs, fish, milk, peanuts, pork, potatoes, tomatoes, wheat germ, whole wheat products.
Herbs that contain niacin include:
alfalfa, burdock root, catnup, cayenne, chamomile, chickweed, eyebright, fennelseed, hops, licorice, mullein, nettle, oak straw, parsley, peppermint, raspberry leaf, red clover, rose hips, slippery elm and yellow dock.b