What are the uses and dosages of bismuth subsalicylate?

Bismuth Subsalicylate: Clinical Uses and Dosing

Primary Indications

Bismuth subsalicylate is FDA-approved for treating traveler's diarrhea, acute diarrhea, upset stomach, heartburn, indigestion, nausea, gas, belching, and fullness due to overindulgence in food or drink. 1

Gastrointestinal Symptom Relief

• For acute diarrhea and traveler's diarrhea: The standard dose is 262 mg (typically 2 tablets) every 30-60 minutes as needed, with a maximum of 8 doses (4.2 g total) in 24 hours 1, 2
• For upset stomach symptoms (heartburn, indigestion, nausea, gas): Same dosing as above—262 mg every 30-60 minutes as needed, maximum 8 doses per 24 hours 1, 2
• Clinical improvement in traveler's diarrhea occurs within 4-24 hours, with significant reduction in unformed stools and subjective symptoms including nausea and abdominal cramping 3

Helicobacter pylori Eradication (Bismuth Quadruple Therapy)

Bismuth subsalicylate is a critical component of first-line quadruple therapy for H. pylori, particularly in areas with high clarithromycin resistance (>15-20%). 4, 5

Complete Quadruple Therapy Regimen:

• Bismuth subsalicylate: 262 mg (2 tablets) 4 times daily, taken 30 minutes before meals 6, 4
• Tetracycline: 500 mg 4 times daily, taken 30 minutes after meals 6, 4
• Metronidazole: 500 mg 4 times daily, taken 30 minutes after meals 6, 4
• Proton pump inhibitor: Standard dose twice daily (e.g., omeprazole 20 mg, esomeprazole 20 mg, rabeprazole 20 mg) taken 30 minutes before meals 6, 4
• Duration: 14 days is the recommended duration per Toronto Consensus and Maastricht V/Florence guidelines; ACG considers 10-14 days acceptable 6, 4

Microscopic Colitis

For symptomatic microscopic colitis when budesonide is not feasible, bismuth salicylate is recommended as a second-line alternative. 6

• Dosing: 262 mg tablets, 3 times daily (8-9 tablets total per day) 6
• This represents a significant pill burden but may be appropriate when corticosteroids are contraindicated or cost is prohibitive 6
• Clinical response was demonstrated in 100% of treated patients versus 0% in placebo in a small randomized trial 6

Prophylaxis for Traveler's Diarrhea

• Preventive dosing: 262 mg (2 tablets) 4 times daily during period of risk 7
• Tablet formulation at 2.1 g/day was 65% effective in preventing traveler's diarrhea during a 3-week trial 7
• Liquid preparation at 60 mL 4 times daily (4.2 g/day) was 62% effective over 3 weeks 7

Critical Safety Considerations

Duration Limits

Treatment with bismuth-containing compounds should not exceed 6-8 weeks, followed by an 8-week bismuth-free interval. 8

• Approximately 0.2% of ingested bismuth is absorbed and sequestered in multiple tissue sites, even with conventional dosing 8
• Prolonged use carries risk of bismuth toxicity, though this is rare with bismuth subsalicylate compared to other bismuth salts 8

Important Warnings

• Black stools: Bismuth causes harmless black discoloration of stools that must be distinguished from melena (GI bleeding) 9

  • Unlike melena, bismuth-related black stools are not tarry in consistency and lack the characteristic foul odor 9
  • Consider temporarily discontinuing bismuth when actual melena is a clinical concern 9

• Salicylate-related precautions: Contains salicylate, which carries risk of Reye syndrome in children with varicella or influenza-like illness 6

• Drug interactions: Potential interactions with anticoagulants, antidiabetic agents, aspirin, corticosteroids, diuretics, and methotrexate due to salicylate component 6

Contraindications

• Known hypersensitivity to bismuth subsalicylate or salicylates 6
• Children with viral infections (varicella, influenza) due to Reye syndrome risk 6

Mechanism of Action

• The salicylate moiety exerts antisecretory effects in diarrheal illness 7
• Bismuth and intestinal hydrolysis products have direct antimicrobial effects against enteric pathogens including toxigenic E. coli and H. pylori 7, 8
• In H. pylori infection, bismuth acts as an antimicrobial agent and improves efficacy even in the presence of metronidazole resistance 4, 5

Common Pitfalls to Avoid

• Do not substitute doxycycline for tetracycline in H. pylori quadruple therapy—results are significantly inferior 6, 4
• Do not use bismuth quadruple therapy for less than 14 days when treating H. pylori, as shorter durations reduce eradication rates 6, 4
• Do not exceed 8 doses (4.2 g) in 24 hours for acute symptom relief 1, 2
• Do not continue bismuth therapy beyond 6-8 weeks without an 8-week drug-free interval 8