AMPICILLIN AND AMOXICILLIN ARE SIMILAR ANTIBIOTICS BUT AREN’T INTERCHANGEABLE. LEARN HOW THEIR USES, DOSING, EFFECTIVENESS, AND COSTS COMPARE.
Ampicillin and amoxicillin belong to the aminopenicillin class of beta-lactam antibiotics. Both treat bacterial infections by preventing bacteria from building protective cell walls, causing them to die. Although they work similarly and treat various infections, they differ in certain uses, dosing, and absorption.
Key Takeaways
Ampicillin and amoxicillin are broad-spectrum antibiotics belonging to the aminopenicillin group of the penicillin family.
Both antibiotics have similar side effects, including nausea, vomiting, diarrhea, and skin rashes. Severe allergic reactions require immediate medical attention.
Both medications are generally covered by insurance and Medicare Part D, but amoxicillin is prescribed more frequently because it is better absorbed when taken orally.
Ampicillin vs. Amoxicillin: Uses, Effectiveness, Side Effects, and Cost
Ampicillin and amoxicillin are broad-spectrum antibiotics belonging to the penicillin family. Although they work similarly, they differ in absorption, dosing, and certain medical uses.
Ampicillin vs. Amoxicillin at a Glance
| Ampicillin | Amoxicillin |
|---|---|
| Less commonly prescribed | More commonly prescribed |
| Usually taken every 6 hours | Usually taken every 8–12 hours |
| Available orally and by injection | Primarily taken orally |
| Lower oral absorption | Better oral absorption |
| Often used for certain Enterococcus and Listeria infections | Commonly used for ear, sinus, throat, and respiratory infections |
What Are the Main Differences?
Ampicillin treats various gram-positive and gram-negative bacterial infections. It is available as generic capsules and injections. It is also combined with sulbactam in the injectable antibiotic Unasyn to expand coverage against certain resistant bacteria. Amoxicillin belongs to the same antibiotic class but is absorbed more effectively when taken orally. It is available as tablets, capsules, chewable tablets, and oral suspensions. It can also be combined with clavulanic acid, commonly known as Augmentin.
Both antibiotics may be prescribed to adults and children. Dosage and treatment duration depend on the infection.
Conditions Treated by Ampicillin and Amoxicillin
Both medications treat susceptible bacterial infections, but their approved uses differ.
Ampicillin
According to its prescribing information, ampicillin may be used for:
Certain respiratory tract infections
Urinary tract infections
Gastrointestinal infections caused by susceptible bacteria
Certain bacterial meningitis infections
Amoxicillin
According to its FDA drug label, amoxicillin may treat:
Ear, nose, and throat infections
Certain urinary tract infections
Skin and soft tissue infections
Lower respiratory tract infections
H. pylori infections when combined with other medications
Neither antibiotic works against viral illnesses such as colds or influenza.
Which Antibiotic Works Better?
Amoxicillin is generally preferred for many outpatient infections because it is absorbed more efficiently and produces more consistent blood concentrations when taken orally. Ampicillin remains useful for certain infections, particularly when intravenous treatment is needed in hospitals.
Both medications can be effective against susceptible bacteria. However, the best choice depends on the infection, bacterial resistance, medical history, and other medications. Healthcare providers may use bacterial cultures and antibiotic susceptibility testing to determine the most appropriate treatment.
Ampicillin vs. Amoxicillin: Cost and Insurance Coverage
oth antibiotics are available as affordable generic medications and are typically covered by commercial insurance and Medicare Part D.
Based on the supplied pricing information:
| Medication | Estimated Price Without Insurance | Typical Medicare Part D Copay |
|---|---|---|
| Ampicillin, 28 capsules of 500 mg | $22 | $0–$1 |
| Amoxicillin, 21 capsules of 500 mg | $12 or more | $0–$1 |
Actual costs depend on dosage, quantity, pharmacy, location, and insurance benefits.
Common Side Effects
Ampicillin and amoxicillin have similar side effects, primarily affecting the digestive system.
Common reactions include:
Nausea
Vomiting
Diarrhea
Skin rashes
Digestive discomfort
Both antibiotics may also increase the likelihood of yeast infections. Severe allergic reactions, including anaphylaxis, require immediate emergency medical attention. Contact your healthcare provider if symptoms become severe or unusual.
Drug Interactions
Because these antibiotics are chemically similar, they share several possible drug interactions.
Warfarin: May increase or alter bleeding risk, requiring monitoring.
Allopurinol: May increase the likelihood of skin rashes.
Hormonal contraceptives: These antibiotics generally do not reduce effectiveness, but severe vomiting or diarrhea may interfere with oral contraceptive absorption.
Live oral typhoid vaccine: Antibiotics may reduce the vaccine’s effectiveness.
Always inform your healthcare provider about medications, supplements, and vaccines before starting treatment.
Important Warnings
Both antibiotics should be used only when prescribed for a bacterial infection.
Important precautions include:
Penicillin allergies: Individuals with previous serious allergic reactions to penicillin may need alternative antibiotics.
Severe diarrhea: Antibiotics can cause Clostridioides difficile infections, which may develop during or after treatment.
Fungal infections: Prolonged antibiotic use may increase the risk of yeast infections.
Antibiotic resistance: Unnecessary or incorrect antibiotic use can contribute to bacterial resistance.
Follow your prescribed treatment instructions and contact your healthcare provider if symptoms worsen or fail to improve.
Frequently Asked Questions
Are Ampicillin and Amoxicillin the Same?
No. Both belong to the aminopenicillin family, but they differ in oral absorption, dosing schedules, formulations, and certain approved uses.
Can You Be Allergic to Both?
Yes. Because the medications are closely related, an allergy to one may indicate a risk of reacting to the other. Inform your healthcare provider about any previous penicillin allergy.
Do They Treat the Same Infections?
They overlap in treating certain bacterial infections, but they are not interchangeable. Amoxicillin is more commonly used for outpatient respiratory, ear, and throat infections, while ampicillin is frequently used intravenously for specific hospital-treated infections.
Is Amoxicillin a Newer Version of Ampicillin?
Both antibiotics were developed decades ago. Amoxicillin became more commonly prescribed for oral treatment because of its better absorption.
Which Is More Effective?
Neither is universally better. Effectiveness depends on the bacteria involved, antibiotic susceptibility, infection severity, and route of administration.
Can They Be Used During Pregnancy?
Both antibiotics may be prescribed during pregnancy when medically appropriate. A healthcare provider should evaluate the potential benefits and risks before treatment.
Can You Drink Alcohol While Taking Them?
Alcohol does not have a major direct interaction with either medication, but it may worsen nausea, digestive discomfort, and dehydration. Avoiding alcohol while recovering from an infection may be helpful.
Are These Strong Antibiotics?
Both are broad-spectrum antibiotics, meaning they work against several types of susceptible bacteria. However, their effectiveness depends on the infection rather than being classified as stronger or weaker.
How Long Should Treatment Last?
Treatment may last approximately 7–14 days, although shorter or longer courses may be appropriate depending on the infection.
Follow the exact duration prescribed by your healthcare provider. Do not stop, extend, or change treatment without medical guidance.
What Bacteria Do They Treat?
Both antibiotics work against certain susceptible gram-positive and gram-negative bacteria responsible for respiratory, urinary, gastrointestinal, and other infections.
Their effectiveness depends on bacterial susceptibility and resistance patterns.
The Bottom Line
Ampicillin and amoxicillin are related penicillin antibiotics used to treat various bacterial infections.Amoxicillin is more commonly prescribed for oral treatment because of its better absorption, while ampicillin is frequently used in hospital settings where injectable antibiotics are needed.
Both medications have similar side effects and drug interactions and are generally available as affordable generics.The appropriate antibiotic depends on the infection, bacterial susceptibility, medical history, and treatment requirements. Always follow your healthcare provider’s prescription and guidance.
Source: SingleCare