[mrsD]

There is so little mannitol in it and it is not absorbed.
I seriously doubt it. Large (and I mean large) amounts can be laxative in some people, esp the xylitol. If you chew sugarless gum or have sugarless mints, either mannitol or xylitol is in them as well

Timed release is useless-- to absorb orally you need immediate presence in the small intestine to work. Empty stomach is best as well. Timed release just doesn't release enough fast enough.
I don't know why it is made even...maybe because it "sounds" good?

The amount absorbed from 1000mcg B12 tablet is about 10micrograms thereabouts.. that is a minute amount.

These are the inert ingredients for Puritan's methyl B12--

Other Ingredients:Other Ingredients: Mannitol, Cellulose (Plant Origin), Silica, Vegetable Cellulose, Vegetable Stearic Acid, Vegetable Magnesium Stearate, Natural Cherry Flavor.

No Artificial Flavor or color, No Preservatives, No Sugar, No Milk, No Lactose, No Soy, No Gluten, No Yeast,, Sodium Free.

This from the website:
http://www.puritan.com/vitamin-b-12-...000-mcg-032860

Exactly what reactions are you having?
I'd get that homocysteine tested... to see if you are not methylating properly. Consuming folic acid....also is a problem if you are not methylating.