What Antibiotics Are Used to Treat H. pylori?

The antibiotics most commonly used to treat H. pylori infection are amoxicillin, clarithromycin, metronidazole, and tetracycline, almost always prescribed in combinations of two or more alongside an acid-suppressing drug. No single antibiotic works reliably on its own against this bacterium, so treatment revolves around multi-drug regimens that typically last 10 to 14 days. Which specific combination your doctor chooses depends on local resistance patterns, whether you have drug allergies, and whether a previous attempt at eradication has already failed.

The Core Antibiotics and How They Are Combined

Four antibiotics do most of the heavy lifting in H. pylori treatment worldwide. Amoxicillin (a penicillin-type antibiotic) and clarithromycin (a macrolide) are the backbone of traditional triple therapy, where they are paired with a proton pump inhibitor (PPI) such as omeprazole or lansoprazole. Metronidazole, an antibiotic effective against many anaerobic organisms, shows up in both triple and quadruple regimens. Tetracycline appears most often in bismuth-based quadruple therapy. Beyond these four, levofloxacin (a fluoroquinolone) and rifabutin serve as rescue options when standard regimens fail.

These drugs are not interchangeable parts you can swap freely. Each combination has a specific rationale. Clarithromycin attacks the bacterium’s protein-making machinery. Amoxicillin disrupts cell wall construction. Metronidazole damages bacterial DNA. Tetracycline blocks protein synthesis by a different route than clarithromycin. Using two antibiotics that work through different mechanisms makes it harder for H. pylori to develop resistance to both simultaneously.

First-Line Regimens

When you are treated for H. pylori for the first time, your doctor will typically choose one of two broad strategies: clarithromycin-based therapy or bismuth quadruple therapy.

Clarithromycin-based triple therapy pairs a PPI with clarithromycin and either amoxicillin or metronidazole. For years this was the default first choice, but rising clarithromycin resistance has eroded its reliability. Even in regions where resistance remains relatively low, eradication rates above 95% are rare with this approach.¹ A large analysis of U.S. military patients found that clarithromycin triple therapy (using either metronidazole or tinidazole alongside amoxicillin) cleared infection in roughly 72–82% of cases, depending on the specific drug combination and population.²

Bismuth quadruple therapy takes a different approach. It combines a PPI with a bismuth salt (like bismuth subsalicylate or bismuth subcitrate), tetracycline, and metronidazole. The advantage here is that bismuth itself has direct antibacterial effects against H. pylori, and no resistance to bismuth has been reported.³ That same Department of Defense study found tetracycline-based bismuth quadruple therapy cleared infection in about 85% of patients overall, making it the most effective regimen in their dataset.² A multicenter real-world study in elderly patients reported per-protocol eradication rates near 89–95% with a 10-day bismuth quadruple regimen, with comparable tolerability between older and younger adults.⁴

A concomitant quadruple therapy, which uses a PPI plus amoxicillin, clarithromycin, and metronidazole all at once (no bismuth), is another first-line option. A prospective trial comparing this non-bismuth quadruple regimen to traditional bismuth quadruple therapy found no statistically significant difference in eradication rates between the two, though both fell below 80% in that particular study population.⁵

Why Bismuth Matters

Bismuth deserves its own mention because it is not technically an antibiotic, yet it plays a pivotal role. Bismuth compounds kill H. pylori through multiple pathways at once: they form complexes in the bacterial cell wall, shut down key enzymes the bacterium needs for energy production, and block the bacterium’s ability to stick to the stomach lining.³ Proteomic research has shown bismuth also suppresses major virulence factors and disrupts the flagella H. pylori uses to burrow into the mucus layer of the stomach.⁶

Perhaps the most clinically useful feature of bismuth is its ability to overcome antibiotic resistance. Strains of H. pylori that are resistant to metronidazole or clarithromycin can become susceptible again when those antibiotics are administered together with bismuth.³ The main downside is pill burden and side effects. Bismuth turns your stool black (harmless, but startling if you are not expecting it), and the regimens that include it require more pills per day than triple therapy.

Vonoprazan-Based Regimens

Vonoprazan is a newer acid-suppressing drug that works differently from PPIs. While PPIs need time to build up and depend on the acid-producing pumps being active, vonoprazan blocks acid secretion more quickly and more completely. This matters for H. pylori treatment because most of the antibiotics work better at higher stomach pH.

A pivotal clinical trial conducted in the U.S. and Europe compared vonoprazan triple therapy (vonoprazan plus amoxicillin and clarithromycin) and vonoprazan dual therapy (vonoprazan plus amoxicillin alone) against standard PPI triple therapy. Against clarithromycin-sensitive strains, the vonoprazan regimens performed similarly to the PPI regimen. Where vonoprazan truly separated itself was against clarithromycin-resistant strains: vonoprazan triple therapy cleared infection in about 66% of those patients, and vonoprazan dual therapy in about 70%, compared to only 32% for the PPI triple therapy group.⁷ Across all patients regardless of resistance status, vonoprazan triple and dual therapy were both superior to standard PPI triple therapy.

A multicenter study from China explored vonoprazan dual therapy at different doses and durations. The high-dose vonoprazan plus amoxicillin regimen given for 10 days achieved eradication rates around 87–91%, which was not inferior to 14 days of the same high-dose regimen. A lower dose, however, performed significantly worse.⁸ The appeal of vonoprazan dual therapy is its simplicity: just two drugs instead of three or four, with potentially fewer side effects. For patients allergic to penicillin, vonoprazan can be combined with clarithromycin and metronidazole instead, with encouraging eradication rates and good tolerability.⁹

Sequential and Concomitant Therapy Variations

Some regimens stagger the antibiotics rather than giving them all simultaneously. In sequential therapy, you take a PPI with amoxicillin for the first five to seven days, then switch to a PPI with clarithromycin and metronidazole for another five to seven days. The idea is that amoxicillin weakens the bacterial cell wall first, making the bacteria more vulnerable to clarithromycin and metronidazole in the second phase.

Concomitant therapy gives all three antibiotics (amoxicillin, clarithromycin, and metronidazole) together with a PPI for the entire course. A meta-analysis found concomitant therapy outperformed sequential therapy, with the advantage especially pronounced in Asian populations.¹⁰ A systematic review comparing hybrid therapy (a modified sequential approach) to concomitant therapy found no significant difference in eradication rates between the two.¹¹ The tradeoff with concomitant therapy is a higher rate of side effects like diarrhea, nausea, and dizziness compared to sequential therapy, since you are taking more antibiotics simultaneously.¹⁰

How Long Treatment Should Last

Most current regimens run 10 or 14 days. There has been debate over whether the extra four days are worth it. For triple therapy, a head-to-head trial comparing 10 and 14 days of PPI-based triple therapy found essentially identical eradication rates, around 84–85%, with a similar proportion of patients reporting side effects in both groups.¹²

For bismuth quadruple therapy, a randomized trial found 10 days and 14 days equally effective, with per-protocol success rates around 95–96% in both arms. The 10-day course cost about 25% less and caused fewer complaints of fatigue and vomiting.¹³ Similarly, extending sequential therapy from the standard 10 days to 14 days did not push eradication above the 95% threshold researchers were hoping for.¹⁴ The evidence broadly suggests that 10 days is usually sufficient for well-chosen regimens, though some guidelines still recommend 14 days for triple therapy, particularly in areas with higher resistance.

When the First Attempt Fails

Somewhere between 10% and 30% of patients are not cured by their first regimen. When that happens, doctors reach for second-line or “salvage” antibiotics that were not part of the initial course. The most common second-line choice is levofloxacin-based triple therapy: a PPI with levofloxacin and amoxicillin. A study of patients with refractory infection found that a compounded levofloxacin triple regimen achieved eradication in about 89% per protocol when used as a second- or third-line option.¹⁵

If levofloxacin-based therapy also fails, or when the strain is resistant to multiple drug classes, rifabutin-based regimens enter the picture. Rifabutin is an antibiotic normally associated with tuberculosis treatment, and H. pylori resistance to it is still uncommon. It is typically combined with a PPI and amoxicillin or metronidazole.¹⁶ Rifabutin-containing therapy is generally reserved for patients who have already failed two or more eradication attempts.¹⁷

Bismuth quadruple therapy also serves as an effective second-line option, especially after failure of a clarithromycin-based first-line regimen. European registry data showed that when PPI plus clarithromycin and metronidazole failed as first-line therapy (achieving only about 69% eradication), switching to bismuth quadruple therapy for the second attempt cleared infection in about 78% of patients.¹⁸

If You Have a Penicillin Allergy

Amoxicillin is a penicillin, so patients with a genuine penicillin allergy cannot use the majority of first-line regimens. The traditional fallback is a PPI combined with clarithromycin and metronidazole, but this approach has produced modest results, with European registry data showing first-line eradication of only about 69%.¹⁸ The same registry found that bismuth quadruple therapy (PPI, bismuth, tetracycline, metronidazole), which contains no penicillin, performed substantially better at about 91% in first-line use for penicillin-allergic patients.

If the first-line regimen fails and levofloxacin is available, a PPI plus clarithromycin and levofloxacin can be considered as a rescue option, even after two or more previous failures.¹⁹ Where vonoprazan is available, combining it with clarithromycin and metronidazole is another option that appears to be better tolerated than bismuth quadruple therapy, with fewer daily pills.⁹

The Role of Susceptibility Testing

A growing body of evidence favors testing the H. pylori strain for antibiotic resistance before choosing a regimen, rather than prescribing empirically. In one study, susceptibility-guided therapy achieved an eradication rate of about 85%, compared to roughly 58% for empiric therapy using the same drug class.²⁰ That is a substantial gap. A multicenter trial using fecal molecular testing to guide bismuth quadruple therapy selection confirmed that tailored regimens were not inferior to standard empiric bismuth quadruple therapy and showed an edge in per-protocol analysis.²¹

Susceptibility testing is especially valuable after a failed first attempt, because you already know the strain has survived one round of antibiotics. But it can also be used upfront. The practical hurdle is access: culture-based susceptibility testing requires an endoscopy to collect a stomach tissue sample, and not all labs are equipped to culture H. pylori. Newer molecular tests that detect resistance genes from stool samples or biopsies are making the process more accessible.²² Pediatric guidelines from ESPGHAN and NASPGHAN now recommend susceptibility testing before any treatment in children, and suggest avoiding clarithromycin altogether when testing is not available.²³

Side Effects, Gut Disruption, and Probiotics

All H. pylori regimens hit the rest of your gut bacteria as collateral damage. The most common complaints are nausea, diarrhea, metallic taste, and abdominal discomfort. Bismuth quadruple therapy tends to cause more side effects than triple therapy, though most are mild and manageable. About a third of patients on either regimen report at least one adverse event during treatment.¹²

The disruption to your gut microbiome is real and measurable. Eradication therapy worsens the diversity of gut bacteria in the short term, though the microbiome tends to recover over weeks to months.²⁴ Probiotic supplementation alongside antibiotics has shown promise in speeding up that recovery and may modestly improve eradication rates while reducing diarrhea and other digestive side effects.²⁵ Probiotics are not a replacement for antibiotics, but adding them is a reasonable strategy to help your gut weather the treatment course.²⁶

Why Sticking to the Full Course Matters

Compliance is the single most important factor in whether your treatment works.²⁷ Skipping doses or stopping early because you feel better (or because the side effects are annoying) dramatically lowers your chances of clearing the infection and increases the risk that resistant bacteria survive. The regimens are designed so that consistent drug levels over the full treatment period are needed to kill the entire bacterial population.

Some practical steps that help: ask your pharmacist for a blister pack that organizes all the pills by day and time, set phone alarms for each dose, and understand ahead of time that side effects like a metallic taste or dark stools are expected and not dangerous. Knowing what to expect makes it easier to push through the full 10 or 14 days. If side effects are truly intolerable, call your doctor rather than just stopping on your own, because switching to a different regimen is better than an incomplete course.

Smoking, Diet, and Treatment Success

Smoking has a measurable negative effect on treatment outcomes. A study in a high-risk population found that active smokers had roughly twice the odds of treatment failure compared to non-smokers.²⁸ The mechanism likely involves reduced blood flow to the stomach lining and changes in gastric acid secretion that make the antibiotics less effective. If you smoke and are about to start treatment, quitting or at least stopping during the treatment period may improve your chances.

Diet, on the other hand, does not appear to affect eradication rates directly. A prospective cohort study examining different dietary patterns found no significant link between what patients ate and whether their treatment succeeded, even though certain diets were associated with more side effects during treatment.²⁹ You do not need to follow a special diet during H. pylori therapy, though avoiding alcohol and very spicy food can reduce stomach irritation while your gut is already under stress from the antibiotics.

Treating Children

H. pylori treatment in children uses the same core antibiotics as in adults but at weight-based doses. Pediatric guidelines recommend amoxicillin, clarithromycin, and metronidazole as the primary options, with bismuth-containing regimens available for children over 10 years of age at adult-like doses.³⁰ The most significant difference from adult practice is the emphasis on susceptibility testing before treatment. Joint ESPGHAN/NASPGHAN guidelines recommend invasive testing with strain analysis for every child diagnosed with H. pylori, and explicitly advise against using clarithromycin empirically when susceptibility data is not available.²³ This is a stricter standard than what most adult guidelines currently require, reflecting concern about growing resistance and the limited antibiotic options available for younger patients.

Confirming the Infection Is Gone

After finishing treatment, you should not assume the infection is cured. Testing to confirm eradication is standard practice, usually done at least four weeks after completing the antibiotic course. The urea breath test and stool antigen test are the most common non-invasive methods. One wrinkle to be aware of: PPIs, antibiotics, and bismuth compounds can all cause false-negative results on these tests if taken too recently.³¹ Your doctor will usually ask you to stop PPIs for at least two weeks before the follow-up test to avoid this problem. If the test comes back positive, the next step is typically a different regimen from the one that failed, ideally guided by susceptibility testing when available.