A 46-year-old male with a duodenal ulcer and H. pylori infection has a penicillin allergy. Which regimen would be most suitable as first-line treatment?

• A. Lansoprazole 30 mg twice daily, clarithromycin 500 mg twice daily, and metronidazole 400 mg twice daily.
• B. Omeprazole 20 mg bid, amoxicillin 1 g bid, and metronidazole 400 mg bid.
• C. Lansoprazole 30 mg once daily, clarithromycin 500 mg twice daily, and metronidazole 400 mg twice daily.
• D. Pantoprazole 40 mg once daily, metronidazole 200 mg bid.

Answer: (A)

The main idea is choosing an H. pylori regimen that works well in someone with a penicillin allergy by avoiding amoxicillin and using a proton pump inhibitor (PPI) with two antibiotics. This combination—two antibiotics with different mechanisms plus a PPI to raise stomach pH—maximizes eradication and antibiotic stability. The specific regimen pairs a PPI taken twice daily (to ensure sustained acid suppression) with clarithromycin and metronidazole, both given twice daily. The doses shown (PPI 30 mg twice daily, clarithromycin 500 mg twice daily, metronidazole 400 mg twice daily) reflect standard first-line triple therapy for penicillin-allergic patients. It’s preferred over regimens that include amoxicillin (not suitable with penicillin allergy), or a single-dose PPI or regimens missing one of the essential antibiotics, because those alternatives are less effective at eradicating H. pylori.