lansoprazole + bismuth subsalicylate + metronidazole + tetracycline

A quadruple therapy combination used primarily for treating *Helicobacter pylori (H. pylori)* infection, which is often associated with duodenal ulcers. This combination includes a proton pump inhibitor (lansoprazole) and three antimicrobial agents (bismuth subsalicylate, metronidazole, and tetracycline) that work together to eradicate *H. pylori* bacteria. The efficacy of this combination varies significantly based on metronidazole resistance patterns, with higher cure rates reported for metronidazole-sensitive strains (89.7%) compared to metronidazole-resistant strains (41.2%). It is typically administered twice daily for 10 days. Common side effects include temporary darkening of the tongue and stool. Moderate to severe side effects can occur in some patients.