Max and Ruby are having concurrent diarrhea bouts! Sorry to hear the poor guy isn't doing well. Jarrow's brand S boulardii with MOS is what you should get for diarrhea. MOS is a pre-biotic, non-digestible sugar that attracts bad gut bacteria. You can get it at Amazon or your local Vitamin Shoppe. I would avoid using the Flagyl as that kills any beneficial bacteria and can cause the opposite effect of constipation. I used to freak out whenever Ruby had diarrhea and would pop a flagyl in her but I've gotten used to the bouts and now just head straight for the S boulardii as she likes the taste of it in her food and is gentler than an antibiotic.