Dr Peter McCullough explains it in the vid sweetiepiezer posted, that I reposted.
Here’s what I found with a quick search....
... Dr. Michael Goodkin shared in “The Promise of Famotidine as a Possible Low Cost COVID-19 Treatment” the potential of Pepcid, the over-the-counter heartburn drug. In addition to blocking H2 receptors on parietal cells, this drug blocks H2 histamine receptors on mast cells. A type of white blood cell usually associated with allergic phenomena, but which respond to infection and contain many chemicals besides histamine, it turns out there are many of these cells near blood vessels and in the lungs. In the current prescription form (oral or IV), famotidine is used for several conditions, including gastroesophageal reflux disease (GERD), active benign gastric ulcer, and other conditions involving excess stomach acid. An inexpensive and overall safe treatment, over a dozen studies have investigated use targeting COVID-19. Now thanks to funding via the U.S. Department of Defense, Leidos Life Sciences (the former SAIC) leads a ...
It’s an antacid and histamine.

I knew the antacid part, but not that it is a histamine. Thx for the info - I must’ve missed that video.
Everyone has been so chatty lately that I give up getting completely caught up.
Thanks Jane.