Bismuth Subsalicylate

Bismuth subsalicylate is an oral gastrointestinal protectant used for symptomatic treatment of selected diarrheal disorders. Its effects derive from both the bismuth component, which acts mainly in the gut, and salicylate, which is systemically absorbed. It is therefore not equivalent to an inert coating agent or to every other bismuth salt.

Veterinary efficacy is not well established in controlled studies. Where used, it supports symptom management rather than replacing fluid therapy, dietary management or treatment of a specific parasitic, infectious or inflammatory cause. Salicylate sensitivity is particularly relevant in cats.

Group

Antidiarrheal and gastrointestinal protectant

Mechanism of Action

Within the gastrointestinal tract, bismuth subsalicylate yields bismuth-containing compounds and salicylate. Bismuth is thought to provide mucosal protective, toxin-binding and weak antimicrobial effects, including activity relevant to some Helicobacter organisms. The exact contribution of each local effect to veterinary antidiarrheal benefit remains uncertain.

The salicylate component can inhibit prostaglandin-related inflammatory and secretory pathways. This may reduce secretion associated with some forms of enteritis, while systemic absorption explains salicylate-related adverse effects and interactions rather than an exclusively local action.

Symptomatic reduction of diarrhea does not identify its cause or prove eradication of an organism. Formation of dark bismuth compounds can discolor feces, which is a chemical effect of treatment rather than evidence that gastrointestinal bleeding has necessarily occurred.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Diarrhea	Reference only	PO		Historical 1–3 mL/kg total daily orally in divided doses; that earlier passage does not assign a concentration. The separately specified 17.5 mg/mL regimens below are independent alternatives.
Acute diarrhea	3.5 mg/kg	PO	Every 8 h	Up to 5 days; Equivalent to 0.2 mL/kg of 17.5 mg/mL liquid. Do not exceed five days for this regimen.
Acute diarrhea	4.375 mg/kg	PO	Every 4–6 h	Equivalent to 0.25 mL/kg of 17.5 mg/mL liquid.
Higher-dose diarrhea treatment	35 mg/kg	PO	Every 6–8 h	Equivalent to 2 mL/kg of 17.5 mg/mL liquid; monitor salicylate exposure.
Uremic gastritis adjunct	35 mg/kg	PO	Every 6–8 h	Equivalent to 2 mL/kg of 17.5 mg/mL liquid; hydration and underlying disease treatment remain necessary.
Helicobacter combination treatment	Reference only	PO		Bismuth subsalicylate 3.85 mg/kg orally every 4–6 hours (0.22 mL/kg of 17.5 mg/mL liquid), plus metronidazole 15.4 mg/kg every 8 hours and amoxicillin 11 mg/kg every 8 hours for three weeks. This is a complete combination protocol.
Tablet-based Helicobacter combination treatment	Reference only	PO		For 14 days: metronidazole 10 mg/kg orally every 12 hours, amoxicillin 15 mg/kg every 12 hours, and bismuth subsalicylate 262 mg tablets every 12 hours: under 5 kg one-quarter tablet; 5–9.9 kg one-half; 10–24.9 kg one; over 25 kg two. The source leaves an exact 25 kg boundary gap; no product weight-band algorithm is invented.

Cats

Use / stage	Dose	Route	Schedule	Instructions
Diarrhea	Reference only	PO		Historical 1–3 mL/kg total daily orally in divided doses; that earlier passage does not assign a concentration. The separately specified 17.5 mg/mL regimens below are independent alternatives.
Diarrhea	8.75–17.5 mg/kg	PO	Every 12 h	Up to 3 days; Equivalent to 0.5–1 mL/kg of 17.5 mg/mL liquid. Cats are salicylate-sensitive; avoid extending the course.
Frequent-dose diarrhea alternative	Reference only	PO		A historical 0.25 mL/kg of 17.5 mg/mL liquid orally every 4–6 hours is described, but frequent salicylate dosing is specifically discouraged in cats.
Diarrhea in kittens and young cats	17.5–35 mg/animal	PO	Every 6–8 h	Equivalent to 1–2 mL of 17.5 mg/mL liquid. Historical regimen; salicylate sensitivity limits use.
Helicobacter combination treatment	Reference only	PO		Bismuth subsalicylate 3.85 mg/kg orally every 4–6 hours (0.22 mL/kg of 17.5 mg/mL liquid), plus metronidazole 15.4 mg/kg every 8 hours and amoxicillin 11 mg/kg every 8 hours for three weeks. This is a complete combination protocol.

Cattle

Use / stage	Dose	Route	Schedule	Instructions
Diarrhea	Reference only	PO		Calves only. 30 mL orally every 30 minutes for eight doses; concentration is not assigned.
Calf diarrhea	1050 mg/animal	PO	Every 6–12 h	Up to 2 days; Calves: 60 mL of a 17.5 mg/mL product. Confirm the actual corrective-mixture composition before substitution.
Alternative diarrhea treatment	Reference only	PO		2–3 fluid ounces orally two to four times daily; use the explicitly stated 17.5 mg/mL liquid, not an extra-strength product. Fluid-ounce standard is not specified.

Horses

Use / stage	Dose	Route	Schedule	Instructions
Diarrhea	Reference only	PO		1–2 mL/kg orally every 6–8 hours; concentration is not assigned. Foals: 3–4 fluid ounces per 45 kg every 6–8 hours, or 3–4 fluid ounces total every 6–8 hours; foals/adults: 1 fluid ounce per 8 kg three to four times daily. These are separate alternatives using 17.5 mg/mL liquid; no unspecified ounce conversion is applied.
Foal diarrhea	1050 mg/animal	PO	Every 6–12 h	Up to 2 days; Foals: 60 mL of 17.5 mg/mL liquid.

Ferrets

Use / stage	Dose	Route	Schedule	Instructions
Helicobacter combination treatment	Reference only	PO		Alternative 1: metronidazole 20 mg/kg, amoxicillin 30 mg/kg and bismuth subsalicylate 7.5 mg/kg, each orally every 8 hours for 3–4 weeks. Alternative 2: metronidazole and amoxicillin each 20 mg/kg every 12 hours, bismuth 17.5 mg/kg every 8 hours for 21 days, with famotidine 0.5 mg/kg daily and sucralfate 25 mg/kg every 8 hours.

Pigs

Use / stage	Dose	Route	Schedule	Instructions
Piglet diarrhea	35–87.5 mg/animal	PO	Every 6–12 h	Up to 2 days; Baby pigs: equivalent to 2–5 mL of 17.5 mg/mL liquid.

Indications

Symptomatic treatment of selected uncomplicated diarrhea in small and large animals; controlled veterinary outcome evidence is limited.
Adjunctive gastrointestinal protection in selected diarrheal or inflammatory gastrointestinal disorders.
Bismuth-containing multidrug treatment approaches for selected Helicobacter-associated gastrointestinal infections.

Contraindications

Salicylate intolerance or aspirin hypersensitivity; cats are especially susceptible to accumulation.
Use cautiously with preexisting bleeding disorders, pregnancy or lactation; feline salicylate accumulation is a particular concern.

Interactions

Other NSAIDs can increase salicylate-related adverse effects.
Bismuth may reduce absorption of other oral medicines.
Give oral tetracycline at least two hours before bismuth to reduce binding.
Aspirin adds to systemic salicylate exposure.

Adverse effects

Black stools
Salicylate-associated gastrointestinal and systemic adverse effects with overuse

Toxicity

Excessive exposure can cause salicylate toxicity, particularly in cats.

Preparations

Preparation	Form	Strength	Route
Bismuth subsalicylate oral suspension 262 mg/15 mL	Oral Liquid	262 mg / 15 mL	PO
Bismuth Subsalicylate 262 mg tablet	Tablet	262 mg / tablet	PO
Pepto-Bismol regular liquid 525 mg/30 mL 17.5 mg/mL. Do not substitute higher-strength liquids by volume.	Oral Liquid	525 mg / 30 mL	PO

Monitoring and Administration

Account for the salicylate component when considering adverse effects and residues.

Use only the exact formulation specified by a regimen; concentrations differ substantially.

Bismuth is radiopaque and may interfere with gastrointestinal imaging. It also darkens stools; distinguish this from true melena. Monitor hydration and electrolytes with significant diarrhea.

Salicylates can interfere with some urine glucose, ketone and other laboratory assays. Protect liquid from light and freezing.