Clarithromycin and amoxicillin are two of the most familiar names on pharmacy shelves, and they often turn up for the same complaints: sore throats, sinus pain, chest infections, ear infections, and stomach ulcers caused by H. pylori. Sometimes they are even prescribed together. Yet they belong to different antibiotic families, attack bacteria in completely different ways, and come with very different safety profiles.
This clarithromycin vs amoxicillin comparison starts with a spec sheet, then pits the two drugs against each other infection by infection, with a clear “edge” for each matchup. We also cover allergies, side effects, interactions, children, pregnancy, and the situations where the right answer is “both.”
The Spec Sheet
| Feature | Clarithromycin | Amoxicillin |
|---|---|---|
| Antibiotic family | Macrolide | Penicillin (aminopenicillin), a beta-lactam |
| How it works | Blocks the bacterial ribosome, stopping protein production | Blocks enzymes that build the bacterial cell wall, causing the cell to burst |
| Main effect | Mostly stops growth (bacteriostatic); can kill at high levels | Kills bacteria (bactericidal) |
| Covers “atypical” germs (Mycoplasma, Chlamydophila, Legionella)? | Yes | No |
| Affected by beta-lactamase enzymes? | No | Yes (unless combined with clavulanate as Augmentin) |
| Usual adult schedule | Every 12 hours, or once daily extended release | Every 8 or 12 hours |
| Drug interactions | Many (strong CYP3A4 inhibitor) | Few |
| Heart rhythm warning | Yes (QT prolongation; FDA caution in heart disease) | No |
| Signature side effect | Metallic or bitter taste | Diarrhea and rash |
| Pregnancy labeling | Not recommended unless no alternative | Widely used; large reassuring data |
| Use in penicillin allergy | Yes | No |
| Cost (US generics) | Low to moderate | Very low |
A Short History of Two Workhorses
Amoxicillin arrived in the early 1970s as an improved version of ampicillin, absorbed better from the gut and dosed less often. It quickly became the default antibiotic for childhood ear and throat infections and remains one of the most prescribed antibiotics in the world. Clarithromycin came about two decades later, when chemists modified erythromycin to make it acid-stable and easier on the stomach. It reached the US market in the early 1990s, just as the role of H. pylori in ulcers and the importance of atypical pneumonia germs were becoming clear. Each drug arrived to solve a different problem, and that origin still shapes how they are used today.
Pros and Cons at a Glance
Clarithromycin
- Pros: covers atypical bacteria; safe in penicillin allergy; twice-daily or once-daily dosing; core drug for MAC; option in selected H. pylori regimens; good tissue penetration.
- Cons: many drug interactions; QT prolongation; FDA caution in heart disease; metallic taste; rising resistance; not recommended in pregnancy without strong reason.
Amoxicillin
- Pros: reliable against strep and pneumococcus at proper doses; very few interactions; extensive pregnancy and pediatric experience; inexpensive; well-tolerated liquid for children.
- Cons: misses atypical germs; destroyed by beta-lactamase enzymes unless combined with clavulanate; cannot be used in true penicillin allergy; rash is common, especially with viral infections like mono.
Two Very Different Attack Plans
Amoxicillin: breaking the wall
Most bacteria are wrapped in a rigid cell wall made of peptidoglycan. Amoxicillin binds to penicillin-binding proteins, the enzymes that stitch that wall together. As the bacterium grows without being able to repair its wall, it ruptures. This is a fast, lethal effect, but only against bacteria that have this kind of wall and that do not produce enzymes (beta-lactamases) that destroy amoxicillin first.
Clarithromycin: jamming the factory
Clarithromycin works inside the cell, binding to the 50S portion of the bacterial ribosome and blocking protein production. Because it does not need a cell wall to act on, it reaches organisms such as Mycoplasma pneumoniae, which have no wall at all, and bacteria that live inside human cells. It also concentrates in lung tissue and white blood cells. Read more in our clarithromycin uses and how it works guide.
Why the difference matters
These mechanisms explain almost every head-to-head result below. Amoxicillin is excellent against classic “typical” bacteria like Streptococcus. Clarithromycin is the specialist for walled-off or wall-less organisms. Resistance follows different paths for each, which is why one can work when the other fails.
Head-to-Head Matchups by Infection
Round 1: Strep throat
Edge: Amoxicillin. Group A Streptococcus has never developed resistance to penicillins, so amoxicillin (or penicillin) remains first line. Macrolide resistance in strep exists and varies by region, so clarithromycin is reserved for people with penicillin allergy. Details in amoxicillin for strep throat.
Round 2: Ear infections in children
Edge: Amoxicillin. High-dose amoxicillin is the recommended first choice for most childhood ear infections when antibiotics are needed. Clarithromycin is an alternative for allergic children, but resistance among the usual ear germs makes it a weaker option. See amoxicillin for ear infections in kids.
Round 3: Bacterial sinus infections
Edge: Amoxicillin (often as amoxicillin-clavulanate). The Infectious Diseases Society of America’s sinusitis guideline advises against macrolides for empiric treatment because pneumococcal resistance to them is high. Amoxicillin-clavulanate is commonly preferred, with doxycycline as a penicillin-allergy alternative. Clarithromycin still works for some patients but is no longer a first pick. Compare with amoxicillin vs Augmentin.
Round 4: Pneumonia in a healthy adult outpatient
Edge: Amoxicillin, by guideline. The 2019 ATS/IDSA pneumonia guideline lists high-dose amoxicillin (1 g three times daily) as the first option for healthy adults without risk factors, with doxycycline as an alternative. Macrolide monotherapy, including clarithromycin, is allowed only where local pneumococcal macrolide resistance is below 25%, which excludes most of the US.
Round 5: Pneumonia in someone with chronic illness
Edge: Both, together. For outpatients with conditions such as COPD, heart disease, diabetes, or kidney disease, the guideline recommends a beta-lactam (often amoxicillin-clavulanate) plus a macrolide (clarithromycin or azithromycin), or a respiratory fluoroquinolone. Here amoxicillin covers pneumococcus and clarithromycin covers atypical germs. Our clarithromycin for pneumonia and bronchitis guide explains this in detail.
Round 6: “Walking pneumonia” from Mycoplasma
Edge: Clarithromycin. Mycoplasma has no cell wall, so amoxicillin cannot touch it. A macrolide (azithromycin or clarithromycin) or doxycycline is needed. Macrolide-resistant Mycoplasma is common in parts of Asia and has been reported in the US, so failure to improve should prompt a review.
Round 7: Whooping cough (pertussis)
Edge: Clarithromycin. Macrolides are the treatment of choice. Azithromycin is usually preferred, with clarithromycin an accepted alternative. Amoxicillin is not used.
Round 8: Flare-ups of chronic bronchitis (COPD)
Edge: Close; amoxicillin-clavulanate slightly favored. When antibiotics are needed for a flare, amoxicillin, amoxicillin-clavulanate, doxycycline, or a macrolide are all used. Local resistance and allergy history usually decide.
Round 9: H. pylori stomach infection
Edge: Amoxicillin as the more reliable partner. Both drugs feature in H. pylori treatment, often together. But H. pylori resistance to amoxicillin remains rare, while clarithromycin resistance is now so common that the 2024 American College of Gastroenterology guideline advises against clarithromycin regimens unless susceptibility is confirmed. Amoxicillin appears in more of today’s recommended regimens, including vonoprazan dual therapy and rifabutin triple therapy. See clarithromycin for H. pylori.
Round 10: Dental infections
Edge: Amoxicillin. When antibiotics are needed for a tooth infection alongside dental treatment, amoxicillin or penicillin are first choices. Clarithromycin is not a standard dental option in US guidance. See amoxicillin for tooth infection.
Round 11: Urinary tract infections
Edge: Neither is ideal. Clarithromycin does not reliably cover common UTI bacteria. Amoxicillin is used only when a urine culture shows susceptibility or in specific situations. See can amoxicillin treat a UTI.
Round 12: Early Lyme disease
Edge: Amoxicillin. Amoxicillin is a standard option for the erythema migrans rash, alongside doxycycline and cefuroxime. Macrolides are less effective and reserved for people who cannot take those.
Round 13: Mycobacterium avium complex (MAC)
Edge: Clarithromycin. A macrolide is the backbone of MAC treatment. Amoxicillin has no role.
Scorecard Summary
| Infection | Usual edge |
|---|---|
| Strep throat | Amoxicillin |
| Ear infection (child) | Amoxicillin |
| Sinus infection | Amoxicillin / amoxicillin-clavulanate |
| Pneumonia, healthy adult | Amoxicillin |
| Pneumonia with chronic illness | Both, combined |
| Walking pneumonia (Mycoplasma) | Clarithromycin |
| Whooping cough | Clarithromycin |
| COPD flare | Close call |
| H. pylori | Amoxicillin as the more reliable partner |
| Tooth infection | Amoxicillin |
| UTI | Neither, unless culture supports amoxicillin |
| Early Lyme disease | Amoxicillin |
| MAC | Clarithromycin |
| True penicillin allergy | Clarithromycin |
Resistance Profiles Compared
Both drugs have lost ground to resistance, but in different ways.
| Germ | Amoxicillin | Clarithromycin |
|---|---|---|
| Group A Streptococcus | No resistance reported | Resistance present in a minority of strains, varies by region |
| Streptococcus pneumoniae | Usually overcome with high doses | High resistance in much of the US |
| Haemophilus influenzae | Some strains make beta-lactamase (clavulanate helps) | Moderate activity; not a strong option |
| Moraxella catarrhalis | Most strains make beta-lactamase (clavulanate needed) | Generally active |
| Mycoplasma pneumoniae | Inactive (no cell wall) | Active, but resistance rising globally |
| H. pylori | Resistance rare | Resistance common |
Amoxicillin’s weakness, beta-lactamase enzymes, can be fixed by adding clavulanate. Clarithromycin’s weakness, ribosomal mutations and efflux pumps, has no equivalent fix, which is why its role has narrowed over time. Our amoxicillin uses guide covers where amoxicillin still shines.
Dosing and Convenience
| Clarithromycin | Amoxicillin | |
|---|---|---|
| Adult tablets/capsules | 250 mg, 500 mg; 500 mg extended release | 250 mg, 500 mg capsules; 500 mg, 875 mg tablets; chewables |
| Liquid | 125 mg/5 mL, 250 mg/5 mL | Several strengths up to 400 mg/5 mL; high-dose formulations for ear infections |
| Doses per day | 2 (or 1 with extended release) | 2 or 3 |
| Food | Optional (required for extended release) | Optional |
| Typical course | 7 to 14 days | 5 to 10 days |
Three Patient Scenarios
A 34-year-old with a sore throat and a positive strep test
No allergies, no other medicines. Amoxicillin is the clear choice: reliable, inexpensive, well tolerated.
A 19-year-old college student with two weeks of dry cough and a patchy chest X-ray
Walking pneumonia from Mycoplasma is suspected. Amoxicillin would miss it. A macrolide such as clarithromycin or azithromycin, or doxycycline, is the logical pick.
A 72-year-old with COPD, heart failure, and pneumonia
Guidelines favor a beta-lactam plus a macrolide or a fluoroquinolone. Because of his heart disease and medication list, his doctor might choose amoxicillin-clavulanate plus doxycycline or azithromycin over clarithromycin, after reviewing interactions and QT risk.
The Penicillin Allergy Question
Penicillin allergy is clarithromycin’s biggest everyday advantage. Because it is chemically unrelated to penicillin, it is safe for people with a genuine penicillin allergy (unless they are also allergic to macrolides).
The catch is that most people labeled penicillin-allergic are not. The CDC notes that while about 10% of US patients report a penicillin allergy, fewer than 1% are truly allergic when tested. That matters, because an unnecessary allergy label pushes doctors toward broader or less effective drugs, often with more side effects. If your allergy dates back to a childhood rash or a vague family story, ask about allergy testing. Our amoxicillin allergy guide explains how delabeling works.
Side Effects Compared
| Side effect | Clarithromycin | Amoxicillin |
|---|---|---|
| Taste disturbance | Common (metallic or bitter) | Rare |
| Nausea and stomach pain | Common | Occasional |
| Diarrhea | Common | Common |
| Rash | Occasional | More common; very common with mononucleosis |
| Insomnia and vivid dreams | Occasional | Rare |
| Heart rhythm effects | QT prolongation; caution in heart disease | None significant |
| Liver injury | Rare | Rare (more with amoxicillin-clavulanate) |
| C. difficile risk | Present | Present |
| Severe allergic reactions | Rare | Less rare; anaphylaxis possible |
Deep dives are available in clarithromycin side effects and amoxicillin side effects.
Drug Interactions: Not a Fair Fight
This is the starkest difference between the two. Amoxicillin has only a handful of notable interactions, such as raised INR with warfarin in some people, more rash with allopurinol, and reduced clearance of methotrexate. Clarithromycin strongly blocks CYP3A4 and P-glycoprotein, affecting statins, colchicine, calcium channel blockers, anticoagulants, sedatives, diabetes drugs, erectile dysfunction drugs, and more. If you take several regular medicines, amoxicillin is often the simpler option when both would work. Our clarithromycin drug interactions guide lists the details.
Heart Safety
Amoxicillin has no meaningful heart rhythm effect. Clarithromycin can prolong the QT interval, and the FDA has advised caution in people with heart disease after long-term follow-up of a trial in patients with coronary disease found more deaths in the clarithromycin group. For someone with heart disease, amoxicillin is usually preferred when it is an appropriate choice. Read clarithromycin heart risks for the full context.
Children
Both drugs come as liquids. Amoxicillin suspension is usually better tolerated and tastes better, which helps children finish the course. Clarithromycin suspension is notoriously bitter. Amoxicillin is dosed every 8 or 12 hours depending on the infection; clarithromycin every 12 hours. Dosing details are in amoxicillin dosage and clarithromycin dosage.
Pregnancy and Breastfeeding
Amoxicillin has decades of reassuring pregnancy data and is one of the most commonly used antibiotics in pregnancy (see amoxicillin during pregnancy). Clarithromycin’s US labeling advises against use in pregnancy unless no appropriate alternative exists, because of findings in animal studies. When a macrolide is needed in pregnancy, azithromycin is usually chosen. Both drugs pass into breast milk in small amounts.
Alcohol
Neither drug has a dangerous direct interaction with alcohol. The key exception arises when clarithromycin is part of an H. pylori regimen that includes metronidazole. See clarithromycin and alcohol and amoxicillin and alcohol.
Kidney and Liver Considerations
Both drugs need dose adjustments in significant kidney impairment, but for different reasons. Amoxicillin is cleared mainly by the kidneys, so the dosing interval is extended when kidney function is low. Clarithromycin is cleared by both the liver and the kidneys; its dose is halved in severe kidney impairment, and its liver-based interactions become more important when either organ is impaired. Clarithromycin has a rare but recognized risk of hepatitis; amoxicillin alone rarely affects the liver, though amoxicillin-clavulanate is a well-known cause of drug-induced liver injury. If you have liver or kidney disease, mention it before either drug is prescribed.
Can You Take Clarithromycin and Amoxicillin Together?
Yes, when a prescriber intends it. The combination is deliberate in two main settings: H. pylori treatment (with an acid blocker), and pneumonia in people with chronic illness or more severe disease (amoxicillin-clavulanate plus a macrolide). There is no harmful interaction between the two antibiotics themselves. Never combine them on your own using leftover tablets.
Where Amoxicillin-Clavulanate Fits In
Many “amoxicillin vs clarithromycin” decisions are really “amoxicillin-clavulanate (Augmentin) vs clarithromycin.” Adding clavulanate protects amoxicillin from beta-lactamase enzymes made by H. influenzae and M. catarrhalis, filling the biggest gap in amoxicillin’s respiratory coverage. That is why amoxicillin-clavulanate is often preferred for bacterial sinusitis, COPD flares, and as the beta-lactam partner in pneumonia combinations. The trade-off is more diarrhea and a slightly higher risk of liver problems than plain amoxicillin. Our amoxicillin vs Augmentin guide covers that comparison in detail.
When Doctors Switch From One to the Other
Switching from amoxicillin to clarithromycin
- A rash or reaction suggests true penicillin allergy.
- Clinical picture shifts toward an atypical infection, such as walking pneumonia or pertussis.
- Testing identifies a germ that clarithromycin covers and amoxicillin does not.
Switching from clarithromycin to amoxicillin (or another drug)
- A serious interaction emerges with a medicine you cannot pause.
- An ECG shows QT prolongation, or heart rhythm symptoms appear.
- Taste disturbance or nausea makes the course impossible to complete.
- Culture results show macrolide resistance.
- You become pregnant during treatment.
Any switch should be made by your prescriber. Combining or substituting leftover tablets on your own risks under-treatment and resistance.
Cost and Availability
Both drugs are available as inexpensive generics in the US, but amoxicillin is among the cheapest prescription medicines of any kind and is stocked almost everywhere. Clarithromycin extended-release tablets and the suspension can cost more and are less consistently stocked. Branded combination packs that contain either drug for H. pylori are considerably more expensive than their generic components. If cost is a concern, ask your pharmacist to compare prices before filling.
Myths vs Facts
- Myth: Clarithromycin is “stronger” than amoxicillin. Fact: Neither is universally stronger. Each is more effective against different bacteria.
- Myth: If amoxicillin did not work, clarithromycin will. Fact: Sometimes, if the cause was an atypical germ or a beta-lactamase producer. But many infections that do not improve are viral, or need a different drug entirely.
- Myth: Clarithromycin is safer because it is not a penicillin. Fact: It avoids penicillin allergy, but brings more interactions and heart rhythm considerations.
If You Are Weighing a Third Option
Azithromycin is clarithromycin’s closest cousin, with shorter courses and fewer interactions. See azithromycin vs clarithromycin and amoxicillin vs azithromycin to complete the comparison.
Frequently Asked Questions
Which is better for a chest infection, clarithromycin or amoxicillin?
For pneumonia in an otherwise healthy adult, US guidelines favor high-dose amoxicillin. For people with chronic illness, a combination is often used. For suspected walking pneumonia, a macrolide or doxycycline is needed. Most ordinary chest colds need neither.
Is clarithromycin a good alternative if I am allergic to amoxicillin?
Yes, for many respiratory and skin infections, provided you are not also allergic to macrolides and your other medicines do not interact. Consider allergy testing if your history is uncertain.
Why do H. pylori regimens contain both?
Using two antibiotics with different mechanisms, plus strong acid suppression, cures more infections and reduces the chance of resistance developing during treatment.
Which has fewer side effects?
Amoxicillin generally causes fewer taste and stomach complaints and has far fewer interactions. It causes more rashes. Overall tolerance depends on the person.
Can I take clarithromycin if amoxicillin gave me a rash?
Often yes, because the two drugs are unrelated. But not every amoxicillin rash is an allergy; rashes during viral infections such as mononucleosis are common and not true allergies. Ask whether testing makes sense before accepting a lifelong penicillin allergy label.
Which is safer if I have heart disease?
Amoxicillin, when it is an appropriate choice for the infection. It has no meaningful QT effect and no FDA heart warning, unlike clarithromycin.
The Bottom Line
Amoxicillin wins most everyday matchups: strep throat, ear infections, sinusitis, uncomplicated pneumonia, dental infections, and pregnancy. Clarithromycin wins where amoxicillin cannot reach: atypical pneumonia, whooping cough, MAC, and true penicillin allergy. In some cases, such as H. pylori and complicated pneumonia, they work best as a team. If you take several medicines or have heart disease, amoxicillin’s clean interaction profile is a real advantage when it fits the infection.
This article is for general education and does not replace personalized advice from your prescriber or pharmacist.
