What are the first‑line and second‑line treatment regimens for Helicobacter pylori infection in adults?

First and Second-Line Treatment for H. pylori Infection

For first-line treatment, use 14-day bismuth quadruple therapy (PPI + bismuth + metronidazole + tetracycline) or 14-day concomitant non-bismuth quadruple therapy (PPI + amoxicillin + metronidazole + clarithromycin), with bismuth quadruple therapy preferred in areas of high clarithromycin resistance (≥15%). 1

First-Line Treatment Regimens

All major consensus guidelines (Toronto, Maastricht V/Florence, and American College of Gastroenterology) agree on prioritizing success on the first attempt to avoid retreatment, reduce costs, and minimize disruption to gut microbiota. 1

Preferred First-Line Options:

Bismuth Quadruple Therapy (PBMT):

• Regimen: PPI (standard dose) twice daily + bismuth ~300mg four times daily + metronidazole 500mg three-four times daily + tetracycline 500mg four times daily 1
• Duration: 14 days (all guidelines agree; 10 days acceptable only if proven locally effective) 1
• Advantages: Effective even with metronidazole-resistant strains, avoids clarithromycin resistance issues, particularly favored in areas with high dual resistance to clarithromycin and metronidazole 1

Concomitant Non-Bismuth Quadruple Therapy (PAMC):

• Regimen: PPI twice daily + amoxicillin 1000mg twice daily + metronidazole 500mg twice daily + clarithromycin 500mg twice daily 1
• Duration: 14 days 1
• Use: Appropriate in areas of high clarithromycin resistance where bismuth is unavailable 1

Restricted First-Line Option:

PPI Triple Therapy (PAC or PMC):

• Regimen: PPI twice daily + amoxicillin 1000mg or metronidazole 500mg twice daily + clarithromycin 500mg twice daily 1
• Duration: 14 days 1
• Restriction: Only use in areas with documented low clarithromycin resistance (<15%) or in patients without previous macrolide exposure 1, 2

Special Consideration - Penicillin Allergy:

In patients with true penicillin allergy, bismuth quadruple therapy is preferred over clarithromycin-based triple therapy with metronidazole, based on superior efficacy in prospective studies. 1

Critical Pitfall:

Levofloxacin therapy is not recommended as first-line treatment by any major guideline, though ACG mentions it as a non-ideal option. 1 Sequential and hybrid therapies are also not recommended as first-line by Toronto and Maastricht guidelines. 1

Second-Line Treatment Regimens

After first-line failure, use either bismuth quadruple therapy (if not used previously) or levofloxacin triple therapy for 14 days, avoiding re-use of antibiotics that failed previously. 1

Key Principle:

Never re-use clarithromycin or levofloxacin after failure, as resistance develops rapidly after exposure. 1 Metronidazole can be re-used if combined with bismuth due to synergistic effects. 1 Amoxicillin and tetracycline can be re-used because resistance remains rare. 1

Preferred Second-Line Options:

Bismuth Quadruple Therapy (PBMT):

• Same regimen as first-line, 14 days 1
• Use if not previously administered or if first-line was clarithromycin-based 1

Levofloxacin Triple Therapy (PAL):

• Regimen: PPI twice daily + amoxicillin 1000mg twice daily + levofloxacin 500mg once daily 1
• Duration: 14 days 1
• Use: Preferred if previous exposure to metronidazole or clarithromycin 1
• Caution: Increasing levofloxacin resistance limits effectiveness; consider susceptibility testing at this stage 1, 3

Alternative Second-Line Options:

Tetracycline-Levofloxacin Quadruple Therapy:

• Regimen: PPI + bismuth + tetracycline + levofloxacin 3
• Evidence: Achieved 98% per-protocol eradication versus 69% with levofloxacin-amoxicillin triple therapy in randomized trials 3
• Advantage: Superior to standard levofloxacin triple therapy, particularly effective against levofloxacin-resistant strains 3

High-Dose Dual Therapy:

• Regimen: High-dose PPI (double standard dose) + amoxicillin 2-3g daily in 3-4 divided doses 1
• Duration: 14 days 1
• Evidence: Achieved 89% per-protocol eradication in second-line treatment 3
• Use: Considered by all guidelines as an option after two failures 1

After Multiple Treatment Failures

After two failed therapies with confirmed adherence, antibiotic susceptibility testing should be performed to guide subsequent regimen selection. 1

If susceptibility testing is unavailable, use antibiotics not previously administered or those with unlikely resistance (amoxicillin, tetracycline, bismuth, or furazolidone). 2

Third-Line and Beyond:

Rifabutin Triple Therapy (PAR):

• Regimen: PPI twice daily + amoxicillin 1000mg twice daily + rifabutin 150mg twice daily or 300mg once daily 1
• Duration: 10 days 1
• Restriction: Reserved for patients who have failed at least 3 prior regimens 1
• Rationale: Rifabutin and amoxicillin resistance remain rare (<15%), making empiric use reasonable without susceptibility testing 1

Important Considerations:

• Treatment duration: All first-line and second-line therapies should be 14 days based on evidence of superior success versus shorter durations 1, 4
• PPI dosing: Standard doses (pantoprazole 40mg, lansoprazole 30mg, omeprazole 20mg, esomeprazole 20mg) twice daily, 30 minutes before meals 1
• Susceptibility testing: Strongly recommended after second-line failure, though not widely available in North America 1
• Local resistance patterns: Treatment selection should ideally be based on local clarithromycin resistance data (≥15% threshold for avoiding triple therapy) 1, 2