In the clinical trial, people with mild to moderate Covid-19 who took very high doses of famotidine, the active ingredient in Pepcid, had some improvement in their symptoms more quickly than those who took a placebo … Among the 55 study participants, those who were assigned to take famotidine had an estimated 50% reduction in symptoms at 8.2 days, and those who were assigned a placebo saw that reduction in 11.4 days.