Table of ContentsView AllTable of ContentsPrimary DifferencesEfficacyDosing GuidelinesStorage RequirementsSide EffectsInteractions
Table of ContentsView All
View All
Table of Contents
Primary Differences
Efficacy
Dosing Guidelines
Storage Requirements
Side Effects
Interactions
Amoxicillinandpenicillin(also known as penicillin V potassium or penicillin G) are two of the most widely-prescribedantibioticsacross the globe.
And from their inception, it’s estimated that millions of lives have been saved due to their effective treatment of bacterial infections, includingrespiratory tract infectionslikepneumoniaorbronchitis.
Amoxicillin and penicillin share a similar chemical structure and work the same way to kill bacteria, so they help treat some of the same types of diseases.
Penicillin generally treats mild to moderate conditions, whereas amoxicillin may treat certain severe infections.
Read on for an in-depth comparison of amoxicillin versus penicillin, including an overview of their uses, dosing, side effects, potential for interaction, and more.
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Primary Differences: Amoxicillin vs. Penicillin
The FDA has approved amoxicillin and penicillin to treat similar types ofbacterial infections. Both drugs are prescribed to treat certain bacterial infections of the ears, nose, throat,urinary tract, skin, and lower respiratory tract.
Examples of bacteria considered susceptible to either amoxicillin or penicillin include certainStreptococcusandStaphylococcusspecies.
In addition, amoxicillin is prescribed as part of a combination drug regimen to treat a stomach infection calledpyloriHelicobacter(H. pylori)andduodenal ulcer disease. Penicillin is not approved to treatH. pylori.
Due to widespread use and overuse, many bacterial infections that were previously treatable with penicillin are now resistant to its effects.
In general, fewer bacteria are resistant to amoxicillin compared to penicillin. However, some bacteria historically treated with amoxicillin may no longer respond to this drug.
Considering recent trends in your area, a healthcare provider can determine which antibiotics may be suitable for treating your infection.
Amoxicillin
Amoxicillin is a generic prescription drug. Brand-name versions include Amoxil and Larotid.
Additionally, amoxicillin is prescribed to treatH. pyloriand duodenal ulcer disease as part of a combination drug regimen.
It is also commonly prescribed to preventbacterial endocarditisassociated with dental procedures.
Finally, used with other drugs, amoxicillin is one of the two active ingredients in the brand-name antibioticAugmentin, which contains amoxicillin and clavulanate acid and can be used for hard-to-treat sinus and ear infections.
Penicillin
Penicillin is also classified as a beta-lactam antibiotic.
Penicillin is a generic prescription drug. There currently isn’t a brand-name version of penicillin V potassium available.
Penicillin works to treat many of the same infections as amoxicillin. Specifically, the FDA has approved penicillin to:
Conversely, penicillin G (an injected form of penicillin that contains potassium and sodium) can be used to treat the following infections:
Before choosing penicillin as an antibiotic to treat a specific infection, healthcare providers typically orderlab teststo identify the bacteria responsible for the condition.
Tests can also help determine if penicillin or another antibiotic will be effective against the bacteria.
Which Is More Effective?
Given the similar nature of amoxicillin and penicillin, only some clinical studies have directly compared the two medications.
An older study investigated the difference between oral amoxicillin and injectable penicillin for pneumonia in children.
The research showed that a similar percentage of participants (81%) in both the penicillin and amoxicillin groups were successfully cured of infection, suggesting similar effectiveness of the two drugs.
Another study compared the effectiveness of amoxicillin vs. penicillin fortonsillitis.
After a 10-day course of either medication, 76% of the participants who took amoxicillin achieved treatment success, compared to 64% of those who took penicillin.
In this study, researchers found amoxicillin more effective than penicillin for tonsillitis.
Overall, these studies suggest relative efficacy between the two products. However, amoxicillin may provide better outcomes for certain infections or strains of bacteria.
Dosage
Both amoxicillin and penicillin are available in a variety of dosage forms and strengths.
When selecting a dosage form, healthcare providers consider several factors, such as personal preferences and the ability to swallow pills or liquids.
No differences in effectiveness exist between the various dosage forms of the same medication.
A healthcare provider may prescribe amoxicillin in the following forms and strengths:
Penicillin V potassium is available in the following forms and strengths:
The dosing recommendations for amoxicillin and penicillin vary depending on the person’s age, weight, type of infection, and severity.
These factors also influence the frequency (number of doses per day) and duration (number of days) of treatment with amoxicillin or penicillin.
Typical dosages of amoxicillin and penicillin are:
You shouldn’t stop treatment early, even if your symptoms go away. Doing so can increase the risk of the infection returning even worse, making it more challenging to treat.
Amoxicillin and penicillin share similar storage requirements. Still, these vary with the dosage form:
Oral capsules and tablets: Keep in a cool, dry area at room temperature in a sealed container.
Oral liquid suspension: Pharmacies store these products in bottles of powder kept at room temperature. After the pharmacist mixes the powder with water, storing the liquid suspension in the refrigerator is recommended. Note the expiration date that your pharmacist adds to the label.
After the product is mixed with water, it usually expires 10 or 14 days later—you should not take the medication after the expiration date.
Side Effects & Safety
Like all drugs, amoxicillin, and penicillin may cause similar side effects. As such, closely monitor yourself or a loved one while taking amoxicillin or penicillin.
If you feel any of the side effects listed below continue to worsen or affect your ability to complete your prescription, contact your healthcare provider immediately.
Common Side Effects
The more common side effects are usually mild and temporary, such as:
Severe Side Effects
In rare instances, treatment with amoxicillin or penicillin leads tosevere, longer-lasting diarrhea, known asClostridioidesdifficile(C. Diff).
This can occur when antibiotics kill the “good” bacteria in your digestive tract and protect it from harmful overgrowth of “bad” bacteria. In these cases, diarrhea could last up to two months and require treatment.
Taking amoxicillin or penicillin infrequently leads to a severe allergic reaction calledanaphylaxis. Symptoms of an allergic reaction include rash, difficulty breathing, and swelling in the face or throat.
Potential for Interaction
Other medications may interact with amoxicillin or penicillin, resulting in side effects or decreased effectiveness.
Some drugs that interact with amoxicillin and penicillin include:
Before starting amoxicillin or penicillin, talk to a healthcare provider about other medications you take.
Sharing this information with your pharmacist can also help prevent interactions that may be dangerous.
Other Safety Considerations
Individuals with a history ofamoxicillin or penicillin allergyshould not receive either medication.
Before starting penicillin or amoxicillin, talk to a healthcare provider if you have an allergy or a history of a reaction to a similar drug.
Regarding pregnancy, no adequate and well-controlled studies show conclusively that the potentially harmful effects of penicillin or amoxicillin on a fetus can be ruled out.
Therefore, amoxicillin and penicillin should only be used in pregnant people if needed.
Additionally, healthcare providers try to avoid prescribing amoxicillin to people with a history ofmononucleosisor “mono” due to a risk of skin reactions.
Summary
Penicillins are a class of antibiotics used against a wide range of bacteria. Both penicillin and amoxicillin are categorized as penicillin-class drugs.
Because of this, the two medications work similarly and are used to treat similar conditions.
Prescribed for conditions such as bacterial infections of the ears, nose, throat, urinary tract, skin, and lower respiratory tract, the varied uses of these two drugs have saved millions of lives since the inception of penicillin in 1941.
Nonetheless, like all drugs, a healthcare provider should decide how and when to use these medications, as their fundamental differences, most notably amoxicillin’s effectiveness against more types of bacteria, may determine which antibiotic a healthcare provider prescribes to treat an infection.
Frequently Asked QuestionsAmoxicillin and penicillin are not expensive. For a one-week supply, both amoxicillin and penicillin cost about $10.50.Mostcommercial and government insurancecover generic drugs at low or no cost to the patient.Both amoxicillin and penicillin are safe for children, but caution should be used in children 3 months and younger.Additionally, depending on the age and weight of a child, the dosing volume for a given bacterial infection may vary.
Frequently Asked Questions
Amoxicillin and penicillin are not expensive. For a one-week supply, both amoxicillin and penicillin cost about $10.50.Mostcommercial and government insurancecover generic drugs at low or no cost to the patient.
Amoxicillin and penicillin are not expensive. For a one-week supply, both amoxicillin and penicillin cost about $10.50.
Mostcommercial and government insurancecover generic drugs at low or no cost to the patient.
Both amoxicillin and penicillin are safe for children, but caution should be used in children 3 months and younger.Additionally, depending on the age and weight of a child, the dosing volume for a given bacterial infection may vary.
Both amoxicillin and penicillin are safe for children, but caution should be used in children 3 months and younger.
Additionally, depending on the age and weight of a child, the dosing volume for a given bacterial infection may vary.
17 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Browne AJ, Chipeta MG, Haines-Woodhouse G, et al.Global antibiotic consumption and usage in humans, 2000-18: a spatial modelling study.Lancet Planet Health. 2021;5(12):e893-e904. doi:10.1016/S2542-5196(21)00280-1Calver, T. University of Oxford.75 years of penicillin in people.MedlinePlus.Penicillin v potassium.MedlinePlus.Amoxicillin.DailyMed.Label: amoxicillin capsules, tablets, and oral suspension, for oral administration.DailyMed.Label: penicillin v potassium tablet penicillin V potassium powder, for solution.Ventola CL.The antibiotic resistance crisis: part 1: causes and threats.P T. 2015;40(4):277-283.Rutherford SJ, Glenny AM, Roberts G, et al.Antibiotic prophylaxis for preventing bacterial endocarditis following dental procedures.Cochrane Database Syst Rev.2022;5(5):CD003813. doi:10.1002/14651858.CD003813.pub5DailyMed.Label: Augmentin- amoxicillin and clavulanate potassium for suspension.Lobanovska M, Pilla G.Penicillin’s discovery and antibiotic resistance: lessons for the future?Yale J Biol Med. 2017;90(1):135-145.MedlinePlus.Penicillin g (potassium, sodium) injection.Addo-Yobo E, Chisaka N, Mumatz H, et al.Oral amoxicillin versus injectable penicillin for severe pneumonia in children aged 3 to 59 months: a randomised multicentre equivalency study.Lancet.2004;364(9440):1141-1148. doi:10.1016/S0140-6736(04)17100-6Curtin-Wirt C, Casey JR, Murray PC, et al.Efficacy of penicillin vs. amoxicillin in children with group A beta hemolytic streptococcal tonsillopharyngitis.Clin Pediatr.2003;42(3):219-225. doi:10.1177/000992280304200305.MedlinePlus.C.diffInfections.American Academy of Allergy Asthma & Immunology.Penicillin allergy FAQ.Gaynes R.The discovery of penicillin—new insights after more than 75 years of clinical use.Emerg Infect Dis. 2017;23(5):849–853. doi:10.3201/eid2305.161556Andrews M, Condren M.Once-daily amoxicillin for pharyngitis.J Pediatr Pharmacol Ther.2010;15(4):244-248.
17 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Browne AJ, Chipeta MG, Haines-Woodhouse G, et al.Global antibiotic consumption and usage in humans, 2000-18: a spatial modelling study.Lancet Planet Health. 2021;5(12):e893-e904. doi:10.1016/S2542-5196(21)00280-1Calver, T. University of Oxford.75 years of penicillin in people.MedlinePlus.Penicillin v potassium.MedlinePlus.Amoxicillin.DailyMed.Label: amoxicillin capsules, tablets, and oral suspension, for oral administration.DailyMed.Label: penicillin v potassium tablet penicillin V potassium powder, for solution.Ventola CL.The antibiotic resistance crisis: part 1: causes and threats.P T. 2015;40(4):277-283.Rutherford SJ, Glenny AM, Roberts G, et al.Antibiotic prophylaxis for preventing bacterial endocarditis following dental procedures.Cochrane Database Syst Rev.2022;5(5):CD003813. doi:10.1002/14651858.CD003813.pub5DailyMed.Label: Augmentin- amoxicillin and clavulanate potassium for suspension.Lobanovska M, Pilla G.Penicillin’s discovery and antibiotic resistance: lessons for the future?Yale J Biol Med. 2017;90(1):135-145.MedlinePlus.Penicillin g (potassium, sodium) injection.Addo-Yobo E, Chisaka N, Mumatz H, et al.Oral amoxicillin versus injectable penicillin for severe pneumonia in children aged 3 to 59 months: a randomised multicentre equivalency study.Lancet.2004;364(9440):1141-1148. doi:10.1016/S0140-6736(04)17100-6Curtin-Wirt C, Casey JR, Murray PC, et al.Efficacy of penicillin vs. amoxicillin in children with group A beta hemolytic streptococcal tonsillopharyngitis.Clin Pediatr.2003;42(3):219-225. doi:10.1177/000992280304200305.MedlinePlus.C.diffInfections.American Academy of Allergy Asthma & Immunology.Penicillin allergy FAQ.Gaynes R.The discovery of penicillin—new insights after more than 75 years of clinical use.Emerg Infect Dis. 2017;23(5):849–853. doi:10.3201/eid2305.161556Andrews M, Condren M.Once-daily amoxicillin for pharyngitis.J Pediatr Pharmacol Ther.2010;15(4):244-248.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Browne AJ, Chipeta MG, Haines-Woodhouse G, et al.Global antibiotic consumption and usage in humans, 2000-18: a spatial modelling study.Lancet Planet Health. 2021;5(12):e893-e904. doi:10.1016/S2542-5196(21)00280-1Calver, T. University of Oxford.75 years of penicillin in people.MedlinePlus.Penicillin v potassium.MedlinePlus.Amoxicillin.DailyMed.Label: amoxicillin capsules, tablets, and oral suspension, for oral administration.DailyMed.Label: penicillin v potassium tablet penicillin V potassium powder, for solution.Ventola CL.The antibiotic resistance crisis: part 1: causes and threats.P T. 2015;40(4):277-283.Rutherford SJ, Glenny AM, Roberts G, et al.Antibiotic prophylaxis for preventing bacterial endocarditis following dental procedures.Cochrane Database Syst Rev.2022;5(5):CD003813. doi:10.1002/14651858.CD003813.pub5DailyMed.Label: Augmentin- amoxicillin and clavulanate potassium for suspension.Lobanovska M, Pilla G.Penicillin’s discovery and antibiotic resistance: lessons for the future?Yale J Biol Med. 2017;90(1):135-145.MedlinePlus.Penicillin g (potassium, sodium) injection.Addo-Yobo E, Chisaka N, Mumatz H, et al.Oral amoxicillin versus injectable penicillin for severe pneumonia in children aged 3 to 59 months: a randomised multicentre equivalency study.Lancet.2004;364(9440):1141-1148. doi:10.1016/S0140-6736(04)17100-6Curtin-Wirt C, Casey JR, Murray PC, et al.Efficacy of penicillin vs. amoxicillin in children with group A beta hemolytic streptococcal tonsillopharyngitis.Clin Pediatr.2003;42(3):219-225. doi:10.1177/000992280304200305.MedlinePlus.C.diffInfections.American Academy of Allergy Asthma & Immunology.Penicillin allergy FAQ.Gaynes R.The discovery of penicillin—new insights after more than 75 years of clinical use.Emerg Infect Dis. 2017;23(5):849–853. doi:10.3201/eid2305.161556Andrews M, Condren M.Once-daily amoxicillin for pharyngitis.J Pediatr Pharmacol Ther.2010;15(4):244-248.
Browne AJ, Chipeta MG, Haines-Woodhouse G, et al.Global antibiotic consumption and usage in humans, 2000-18: a spatial modelling study.Lancet Planet Health. 2021;5(12):e893-e904. doi:10.1016/S2542-5196(21)00280-1
Calver, T. University of Oxford.75 years of penicillin in people.
MedlinePlus.Penicillin v potassium.
MedlinePlus.Amoxicillin.
DailyMed.Label: amoxicillin capsules, tablets, and oral suspension, for oral administration.
DailyMed.Label: penicillin v potassium tablet penicillin V potassium powder, for solution.
Ventola CL.The antibiotic resistance crisis: part 1: causes and threats.P T. 2015;40(4):277-283.
Rutherford SJ, Glenny AM, Roberts G, et al.Antibiotic prophylaxis for preventing bacterial endocarditis following dental procedures.Cochrane Database Syst Rev.2022;5(5):CD003813. doi:10.1002/14651858.CD003813.pub5
DailyMed.Label: Augmentin- amoxicillin and clavulanate potassium for suspension.
Lobanovska M, Pilla G.Penicillin’s discovery and antibiotic resistance: lessons for the future?Yale J Biol Med. 2017;90(1):135-145.
MedlinePlus.Penicillin g (potassium, sodium) injection.
Addo-Yobo E, Chisaka N, Mumatz H, et al.Oral amoxicillin versus injectable penicillin for severe pneumonia in children aged 3 to 59 months: a randomised multicentre equivalency study.Lancet.2004;364(9440):1141-1148. doi:10.1016/S0140-6736(04)17100-6
Curtin-Wirt C, Casey JR, Murray PC, et al.Efficacy of penicillin vs. amoxicillin in children with group A beta hemolytic streptococcal tonsillopharyngitis.Clin Pediatr.2003;42(3):219-225. doi:10.1177/000992280304200305.
MedlinePlus.C.diffInfections.
American Academy of Allergy Asthma & Immunology.Penicillin allergy FAQ.
Gaynes R.The discovery of penicillin—new insights after more than 75 years of clinical use.Emerg Infect Dis. 2017;23(5):849–853. doi:10.3201/eid2305.161556
Andrews M, Condren M.Once-daily amoxicillin for pharyngitis.J Pediatr Pharmacol Ther.2010;15(4):244-248.
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