Bismuth Subsalicylate
Bismuth subsalicylate
Generic Name
Bismuth subsalicylate
Mechanism
- Topical antiseptic/anti‑schistosome: BSS complex binds and neutralizes bacterial endotoxins (e.g., lipopolysaccharide) and inactivates surface‑active molecules in *Giardia* and other enteric organisms.
- Anti‑inflammatory: The subsalicylate moiety inhibits peripheral prostaglandin synthesis locally in the GI mucosa, reducing ulcer pain and inflammation.
- Mucosal protection: BSS forms a sour, greasy coating on the esophageal, gastric, and intestinal epithelium that shields it from gastric acid, facilitating ulcer healing.
- Magnesium effect: BSS releases low concentrations of magnesium, providing symptomatic relief of abdominal cramps.
Together, these actions decrease gastric acid damage, curb colonic inflammation, and treat bacterially‑mediated diarrhea.
Pharmacokinetics
- Absorption: <2 % systemic absorption from the GI tract.
- Distribution: Primarily confined to the GI lumen; minimal plasma distribution.
- Metabolism: Ingested BSS is hydrolysed to bismuth trioxide (Bi₂O₃) and salicylate (aspirin‑like metabolite). Salicylate is further metabolised to salicylic acid and conjugates, while bismuth is largely non‑metabolised.
- Elimination:
- Bismuth: Renally eliminated; half‑life ≈ 20–24 h (may be prolonged in renal dysfunction).
- Salicylates: Excreted via kidney and bile.
- Food interactions: Food minimally affects BSS absorption due to its poor solubility.
Indications
- Acute dyspepsia – gas, bloating, and epigastric pain.
- Acute watery or bloody diarrhea (traveler’s or bacterial) – 1–2 days of therapy; effective against *E. coli*, *Shigella*, *Salmonella*, and *Campylobacter*.
- Helicobacter pylori adjunct therapy – combined with triple or quadruple therapy for ≥14 days.
- Gastric/duodenal ulcer pain – short‑term use for ulcerogenic gastritis.
- Sialorrhea – off‑label for excessive salivation.
Contraindications
- Allergy to aspirin or other NSAIDs (may precipitate salicylate toxicity).
- Pregnancy – category D: risk of premature labor, placental abruption, and fetal toxicity.
- Lactation – not recommended; potential for infant salicylate poisoning.
- Renal impairment – increased risk of bismuth accumulation and neurotoxicity.
- Recurrent or chronic diarrhea – indicates underlying disease requiring further evaluation.
- Current NSAID therapy – additively increases ulcer risk.
Warnings
• Bismuth toxicity: Chronic exposure → neurotoxicity (tremor, ataxia, paresthesias, confusion) and nephrotoxicity.
• Black stool/Tongue: Benign, self‑limiting appearance of feces and mucosa.
• Kidney injury: Monitor creatinine in patients >60 y or with chronic kidney disease.
Dosing
| Population | Typical Dose | Frequency | Duration* | Notes |
| Adults | 500 mg PO every 30–60 min as needed | ≤4 g/day | 2–3 days (acute) | Do not exceed 4 g/day |
| Adults (Traveler’s diarrhea) | 500 mg PO 4×/day | 2–7 days | 7–10 days | Adjunct to antibiotics if severe |
| Adults (H. pylori) | 240 mg PO 4×/day | 14 days | 14 days | Co‑administer with PPIs + 2 antibiotics |
| Pediatric (≥12 yrs) | 125 mg (¼ tablet) PO every 30–60 min | ≤6 mg/kg/day | 2–5 days | Use with caution; avoid in <12 yrs |
*Duration is symptom‑guided; never exceed the stated maximum.
Formulations: 240 mg tablets (BSS), 500 mg capsules (used only for specific indications), or 2 g liquid preparations.
Adverse Effects
Common
• Nausea, vomiting, constipation, abdominal discomfort
• Black discoloration of stool, tongue, nails, or teeth (benign)
Serious
• Bismuth toxicity: neurotoxicity (tremor, ataxia, paresthesia), nephrotoxicity (renal failure, electrolyte imbalance)
• Salicylate toxicity: tinnitus, dizziness, gastrointestinal irritation, bleeding risk (especially in NSAID or aspirin users)
• Allergic reactions: rash, anaphylaxis in aspirin‑allergic patients
Monitoring
- Renal function: Serum creatinine/eGFR at baseline; repeat if >2 weeks of therapy or in patients with CKD.
- Neurologic assessment: Monitor for tremor, confusion, gait disturbances.
- Gastrointestinal signs: Document stool characteristics (black vs. occult bleeding).
- Salicylate levels: If signs of toxicity or in patients on high‑dose aspirin.
Clinical Pearls
1. “Black, black, black” – Positive finding, not a sign of gastrointestinal bleeding.
2. Adjunct in H. pylori – 4‑drug quadruple regimens (PPI + amoxicillin + clarithromycin + BSS) actually improve eradication rates versus triple therapy.
3. Pediatric caution – Avoid BSS in children <12 yrs due to higher risk of bismuth accumulation and salicylate toxicity; use if no alternatives and under supervision.
4. Drug‑drug interactions – Concurrent NSAID use amplifies ulcer risk; avoid combination unless necessary and monitor closely.
5. Renal risk – In CKD stages III‑IV, consider halving the dose or switching to alternative antidiarrheals (e.g., loperamide).
6. Take with water, not milk – Milk may form a insoluble colloid, limiting surface activity.
7. Elder vigilance – The elderly may display prodromal signs of toxicity earlier; ask about tremor, confusion, or renal complaints.
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• *This drug card is intended for educational purposes and complements, not replaces, established clinical guidelines. Always review current literature and institutional protocols before initiating therapy.*