- A reader forward me a link to Bismuth for IBD and IBS-D study from Australia (2013 Full Text) which states:
“Bismuth has antidiarrheal, antibacterial, and anti-inflammatory properties…Bismuth is minimally absorbed and so has negligible potential for toxicity in patients with normal renal function. Any absorbed bismuth is mostly excreted in urine unless renal function is severely impaired…. Although many of these disease entities are known to have spontaneous remissions and relapses, it seems unlikely that the unremitting diarrhea in some of our study patients lasting for months to years, despite being on standard treatment, would suddenly settle in its natural course when bismuth was initiated. “
- They used oral colloidal bismuth subcitrate (CBS) – used in De-nol and Pylera
- Pepto-bismol is bismuth salicylate.
So what more do we know about bismuth?
- ” It is concluded that all patients with irritable bowel syndrome and diarrhea show altered composition of intestinal microflora, morphological signs of moderate chronic inflammation of intestinal mucosa. Most of them have apparent bacterial activity. Treatment with de-nol [bismuth tri-potassium di-citrate] and spasmolytics for 3 weeks effectively eliminated clinical manifestations of the disease, restored normal composition of intestinal microflora, normalized faeces properties, and resolved active inflammation.” 
- Bismuth(III) deferiprone effectively inhibits growth of Desulfovibrio desulfuricans ATCC 27774 .
- “BISMUTH SUBSALICYLATE
Bismuth subsalicyclate (BSS) has been shown to provide up to 65% protection against TD when taken as 2 tablets 4 times per day for a maximum of 3 weeks.25 It is usually well tolerated in young healthy adults. However, clinicians must warn travelers about blackening of the stool or tongue when taking this drug. BSS can decrease absorption of doxycycline, which may be used concomitantly for malaria prophylaxis.26 A careful review of the traveler’s medication list should be performed to look for potential drug-drug interactions. Although BSS provides moderate protection against TD, the need for frequent administration decreases the overall compliance and makes it a less attractive choice for most travelers.” 
- “The percent protection provided by BSS was 62% for the group that received 4.2 g/d, 65% for 2.1 g/d, and 40% for 1.05 g/d, when compared with the corresponding placebo group.” 
- Mitigation of in vitro hydrogen sulfide production using bismuth subsalicylate with and without monensin in beef feedlot diets .
- Saccharomyces boulardii and bismuth subsalicylate as low-cost interventions to reduce the duration and severity of cholera .
- Antimicrobial activity of bismuth subsalicylate on Clostridium difficile, Escherichia coli O157:H7, norovirus, and other common enteric pathogens . “Collectively, our results confirm and build on existing data that BSS has antimicrobial properties against a wide-range of diarrhea-causing pathogens.”
- Effect of licorice versus bismuth on eradication of Helicobacter pylori in patients with peptic ulcer disease. “Our study showed that licorice is as effective as bismuth in H. pylori eradication; therefore, in patients whom bismuth is contraindicated, licorice can be used safely instead.”
- Inadvertent exaggerated anticoagulation following use of bismuth subsalicylate in an enterally fed patient receiving warfarin therapy .
We see above that 2.1 g/day of Pepto-bismol (BSS) appears to be the minimal effective dosage for altering the risk of traveler’s diarrhea (and thus effective protection against some bacteria shifts).
There appears to be significant evidence that it may reduce some symptoms of CFS/FM/IBS in a subset of patients and thus should be discussed with you medical professional. The duration of many studies appear to be approximately 4 weeks.
As always, consult with your medical professional before adding or changing medications.