Metronidazole

Indications

• Diarrhea
• Dyspepsia
• Nausea
• Gastrointestinal upset
• Traveler's diarrhea

Dosage

Children: For children aged 12 years and older, the dose is similar to adults. For children under 12 years, refer to the BNF for Children for appropriate dosing recommendations.

Adults: The typical adult dose is 524 mg to 1050 mg every 30 to 60 minutes as needed, not exceeding 4200 mg per day.

Mechanism of action

Bismuth subsalicylate primarily acts by forming a protective layer on the gastrointestinal mucosa. This action reduces irritation and inflammation. Additionally, it has antibacterial effects that can help eliminate certain pathogens responsible for gastrointestinal upset. The salicylate component contributes to its anti-inflammatory properties, inhibiting prostaglandin synthesis and thereby reducing gastrointestinal motility.

Pharmacodynamics

The pharmacodynamics of bismuth subsalicylate involve its ability to bind to intestinal mucosa, forming a protective barrier that decreases irritation and inflammation. It also exhibits antimicrobial activity against certain bacteria and viruses, which can help reduce the incidence of diarrhea. The salicylate component provides analgesic and anti-inflammatory effects, contributing to symptomatic relief in gastrointestinal disorders.

Pharmacokinetics

Bismuth subsalicylate is minimally absorbed systemically. It primarily acts locally within the gastrointestinal tract. Metabolism occurs in the liver, and the drug is excreted in the feces, where it can exert its therapeutic effects. Due to its minimal systemic absorption, adverse effects are generally localized, and systemic toxicity is rare.

Interactions

• Bismuth subsalicylate with drugs that have anticoagulant effects: Increases risk of bleeding events.
• Opioids with drugs that cause serotonin syndrome: Increases risk of serotonin syndrome.
• Tapentadol with drugs that cause serotonin syndrome: Increases risk of serotonin syndrome.