CFS Since, I want to mention LDN again. Not because I think you should try LDN, but because the theoretical mode of action may shed some light on why Tagamet may work in lower doses. Here's a quick summary. 1) endorphins play an important role in immune system. 2) naltrexone blocks endorphin receptors 3) while those receptors are blocked, naturally produced endorphins are able to 'build up'. 4) in higher doses, naltrexone continues to block those receptors and the natural endorphins are unable to 'do their job'. (leading to the opposite effect, and a worsening of symptoms) 5) with a lower dose, the naltrexone is cleared of the body long before the next dose, allowing endorphins to bind with receptors and exert their influence on the immune system. If you take the basic ideas of this theory and apply them to Tagamet, you might see that a lower dose is worth a try. I have used simple language here, I'm just trying to get the basic point across.