Table of ContentsView AllTable of ContentsCephalexinAmoxicillinDosing GuidelinesOnset to ActionSide EffectsHow to Take SafelyPotential for InteractionWhich One Is Better for Me?Preventing Bacterial InfectionsFrequently Asked Questions

Table of ContentsView All

View All

Table of Contents

Cephalexin

Amoxicillin

Dosing Guidelines

Onset to Action

Side Effects

How to Take Safely

Potential for Interaction

Which One Is Better for Me?

Preventing Bacterial Infections

Frequently Asked Questions

Cephalexinis anantibioticthat treats various bacterial infections such as pneumonia, other respiratory tract infections, and infections of the ears, urinary tract, skin, bone, and genitals. Cephalexin is a member of a class of drugs calledcephalosporins.

Amoxicillinis an antibiotic that treats bacterial infections like pneumonia, bronchitis, and infections of the ears, throat, nose, skin, and urinary tract.Amoxicillinis a member of a class of drugs called penicillin antibiotics.

Antibiotics only treat bacterial infections and are not effective in treating viral infections like thecold or flu.Cephalexin and amoxicillin are both generic prescription antibiotics. They have various similarities and differences. This article will provide information about both antibiotics.

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A close-up of a bottle of amoxicillin antibiotic suspension with a blurred background

What Is Cephalexin and How Does It Work?

Cephalexin is classified as a cephalosporin antibiotic. It is afirst-generation cephalosporin antibiotic, meaning that it was among the first cephalosporins developed. It is also part of a larger class known asbeta-lactam antibiotics. Beta-lactam antibiotics include all cephalosporin drugs as well as all penicillin drugs, including amoxicillin.

Cephalexin is only for treating certain types of bacterial infections. You will not find cephalexin as an ingredient in any other types of medication that are not antibiotics.

Some other examples of off-label uses for cephalexin include:

What Is Amoxicillin and How Does It Work?

Amoxicillin can treat the following types of bacterial infections when the infection is known or thought to be susceptible to amoxicillin treatment:

Amoxicillin can also be found as an ingredient in the antibioticAugmentin.

General dosing guidelines for cephalexin and amoxicillin are as follows.

For adults and adolescents 15 years of age and older, the cephalexin dosage is:

For children over 1 year of age, the dosage will depend on the type and severity of infection as well as the child’s weight.

Amoxicillin dosing is as follows:

Cephalexin starts working quickly, reaching its highest levels in the body within one hour. A dose of cephalexin lasts for about six to eight hours in the body.

Amoxicillin also starts working quickly, reaching its highest levels in the body within an hour or two. A dose of amoxicillin lasts in the body for about five to eight hours.

Regardless of which antibiotic you take, you may start to feel better relatively quickly, possibly within a day or two. However, this does not mean you can stop taking the medicine.

You must finish a course of antibiotics to ensure the infection clears and to prevent bacteria from becomingresistant. If bacteria become resistant to an antibiotic, the antibiotic will not work the next time you need it.

Each medication may have side effects.

Common side effects of cephalexin include:

Common side effects of amoxicillin include:

Serious Side Effects

Call your healthcare provider right away if you experience serious side effects. Call 911 if your symptoms feel life-threatening or you think you have a medical emergency. Serious side effects of cephalexin and amoxicillin can include the following:

Report Side Effects

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Safely Taking Cephalexin vs. Amoxicillin

Here are some tips for safely taking cephalexin or amoxicillin:

Before taking cephalexin or amoxicillin, tell your healthcare provider about all of the medicines you take, including:

While taking cephalexin or amoxicillin, do not start any new medications without approval from your healthcare provider.

Some examples of drug interactions with cephalexin include:

Some examples of drug interactions with amoxicillin include:

This is not a full list of drug interactions. Other drug interactions may occur with cephalexin or amoxicillin. Consult your healthcare provider for more information about drug interactions and how they may affect you.

For example, you should not take cephalexin if you are allergic to cephalexin or any other cephalosporin medication, such as Omnicef (cefdinir) or Ceftin (cefuroxime).You should not take amoxicillin if you are allergic to amoxicillin or penicillins, such aspenicillinorAugmentin (amoxicillin and clavulanic acid).

Because cephalexin and amoxicillin both fall under the broad category of beta-lactam antibiotics, if you are allergic to one, there is a chance you may be allergic to the other. However, in many cases, people who are allergic to penicillin or amoxicillin can safely take cephalexin.You can ask your healthcare provider for personalized medical advice regarding allergies to medications.

Additionally, you should tell your healthcare provider about any medical conditions (especially any problems with your stomach, kidneys, or liver) you have, as well as your medical history and family history. Also, tell your healthcare provider if you are pregnant, planning to become pregnant, or breastfeeding/chestfeeding.

Your healthcare provider can examine you, order necessary tests, and prescribe the appropriate antibiotic for you.

Various types of bacteria cause bacterial infections. Some common examples of bacteria includeStaphylococcus,Streptococcus, andE. coli.Here are some general tips on preventing infections:

Summary

Cephalexin and amoxicillin have some things in common but some differences as well. Consult your healthcare provider for more information about these medications.

Cephalexin or amoxicillin tablets or capsules can be stored at room temperature, away from direct light, heat, and moisture.Cephalexin liquid is stored in the refrigerator. Amoxicillin liquid is generally stored in the refrigerator, but other forms of it can be stored at room temperature. If you or your child is prescribed the liquid formulation, ask your pharmacist about specific storage requirements.Keep all medications out of sight and out of reach of children and pets.Learn MoreTips for Safe Medication Administration

Cephalexin or amoxicillin tablets or capsules can be stored at room temperature, away from direct light, heat, and moisture.Cephalexin liquid is stored in the refrigerator. Amoxicillin liquid is generally stored in the refrigerator, but other forms of it can be stored at room temperature. If you or your child is prescribed the liquid formulation, ask your pharmacist about specific storage requirements.Keep all medications out of sight and out of reach of children and pets.

Cephalexin or amoxicillin tablets or capsules can be stored at room temperature, away from direct light, heat, and moisture.

Cephalexin liquid is stored in the refrigerator. Amoxicillin liquid is generally stored in the refrigerator, but other forms of it can be stored at room temperature. If you or your child is prescribed the liquid formulation, ask your pharmacist about specific storage requirements.

Keep all medications out of sight and out of reach of children and pets.

Learn MoreTips for Safe Medication Administration

Azithromycin, which is usually taken once a day, can treat various bacterial infections such as bronchitis, pneumonia, sexually transmitted infections (STI), and infections of the skin, throat, ears, lungs, sinuses, and reproductive organs.

Learn MoreWhat to Know About Azithromycin

16 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.MedlinePlus.Cephalexin.MedlinePlus.Amoxicillin.Bush K, Bradford PA.β-Lactams and β-lactamase inhibitors: an overview.Cold Spring Harb Perspect Med. 2016;6(8):a025247. doi:10.1101/cshperspect.a025247Prescribers’ Digital Reference (PDR).Cephalexin.National Library of Medicine DailyMed.Cephalexin.Selva Olid A, Solà I, Barajas-Nava LA, et al.Systemic antibiotics for treating diabetic foot infections.Cochrane Database Syst Rev. 2015;2015(9):CD009061. doi:10.1002/14651858.CD009061.pub2Arnold JJ, Hehn LE, Klein DA.Common questions about recurrent urinary tract infections in women.Am Fam Physician. 2016;93(7):560-569Prescribers’ Digital Reference (PDR).Amoxicillin.National Library of Medicine DailyMed.Amoxicillin.Cluver C, Novikova N, Eriksson DOA, et al.Interventions for treating genitalChlamydia trachomatisinfection in pregnancy.Cochrane Database Syst Rev. 2017;(9):CD010485. doi:10.1002/14651858.CD010485.pub2Arvikar SL, Steere AC.Diagnosis and treatment of Lyme arthritis.Infect Dis Clin North Am. 2015;29(2):269-280. doi:10.1016/j.idc.2015.02.004U.S. Food and Drug Administration.Combating antibiotic resistance.Zagursky RJ, Pichichero ME.Cross-reactivity in β-lactam allergy.J Allergy Clin Immunol Pract. 2018;6(1):72-81.E1. doi:10.1016/j.jaip.2017.08.027MedlinePlus.Bacterial infections.Harvard Health Publishing.How to prevent infections.MedlinePlus.Azithromycin.

16 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.MedlinePlus.Cephalexin.MedlinePlus.Amoxicillin.Bush K, Bradford PA.β-Lactams and β-lactamase inhibitors: an overview.Cold Spring Harb Perspect Med. 2016;6(8):a025247. doi:10.1101/cshperspect.a025247Prescribers’ Digital Reference (PDR).Cephalexin.National Library of Medicine DailyMed.Cephalexin.Selva Olid A, Solà I, Barajas-Nava LA, et al.Systemic antibiotics for treating diabetic foot infections.Cochrane Database Syst Rev. 2015;2015(9):CD009061. doi:10.1002/14651858.CD009061.pub2Arnold JJ, Hehn LE, Klein DA.Common questions about recurrent urinary tract infections in women.Am Fam Physician. 2016;93(7):560-569Prescribers’ Digital Reference (PDR).Amoxicillin.National Library of Medicine DailyMed.Amoxicillin.Cluver C, Novikova N, Eriksson DOA, et al.Interventions for treating genitalChlamydia trachomatisinfection in pregnancy.Cochrane Database Syst Rev. 2017;(9):CD010485. doi:10.1002/14651858.CD010485.pub2Arvikar SL, Steere AC.Diagnosis and treatment of Lyme arthritis.Infect Dis Clin North Am. 2015;29(2):269-280. doi:10.1016/j.idc.2015.02.004U.S. Food and Drug Administration.Combating antibiotic resistance.Zagursky RJ, Pichichero ME.Cross-reactivity in β-lactam allergy.J Allergy Clin Immunol Pract. 2018;6(1):72-81.E1. doi:10.1016/j.jaip.2017.08.027MedlinePlus.Bacterial infections.Harvard Health Publishing.How to prevent infections.MedlinePlus.Azithromycin.

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.

MedlinePlus.Cephalexin.MedlinePlus.Amoxicillin.Bush K, Bradford PA.β-Lactams and β-lactamase inhibitors: an overview.Cold Spring Harb Perspect Med. 2016;6(8):a025247. doi:10.1101/cshperspect.a025247Prescribers’ Digital Reference (PDR).Cephalexin.National Library of Medicine DailyMed.Cephalexin.Selva Olid A, Solà I, Barajas-Nava LA, et al.Systemic antibiotics for treating diabetic foot infections.Cochrane Database Syst Rev. 2015;2015(9):CD009061. doi:10.1002/14651858.CD009061.pub2Arnold JJ, Hehn LE, Klein DA.Common questions about recurrent urinary tract infections in women.Am Fam Physician. 2016;93(7):560-569Prescribers’ Digital Reference (PDR).Amoxicillin.National Library of Medicine DailyMed.Amoxicillin.Cluver C, Novikova N, Eriksson DOA, et al.Interventions for treating genitalChlamydia trachomatisinfection in pregnancy.Cochrane Database Syst Rev. 2017;(9):CD010485. doi:10.1002/14651858.CD010485.pub2Arvikar SL, Steere AC.Diagnosis and treatment of Lyme arthritis.Infect Dis Clin North Am. 2015;29(2):269-280. doi:10.1016/j.idc.2015.02.004U.S. Food and Drug Administration.Combating antibiotic resistance.Zagursky RJ, Pichichero ME.Cross-reactivity in β-lactam allergy.J Allergy Clin Immunol Pract. 2018;6(1):72-81.E1. doi:10.1016/j.jaip.2017.08.027MedlinePlus.Bacterial infections.Harvard Health Publishing.How to prevent infections.MedlinePlus.Azithromycin.

MedlinePlus.Cephalexin.

MedlinePlus.Amoxicillin.

Bush K, Bradford PA.β-Lactams and β-lactamase inhibitors: an overview.Cold Spring Harb Perspect Med. 2016;6(8):a025247. doi:10.1101/cshperspect.a025247

Prescribers’ Digital Reference (PDR).Cephalexin.

National Library of Medicine DailyMed.Cephalexin.

Selva Olid A, Solà I, Barajas-Nava LA, et al.Systemic antibiotics for treating diabetic foot infections.Cochrane Database Syst Rev. 2015;2015(9):CD009061. doi:10.1002/14651858.CD009061.pub2

Arnold JJ, Hehn LE, Klein DA.Common questions about recurrent urinary tract infections in women.Am Fam Physician. 2016;93(7):560-569

Prescribers’ Digital Reference (PDR).Amoxicillin.

National Library of Medicine DailyMed.Amoxicillin.

Cluver C, Novikova N, Eriksson DOA, et al.Interventions for treating genitalChlamydia trachomatisinfection in pregnancy.Cochrane Database Syst Rev. 2017;(9):CD010485. doi:10.1002/14651858.CD010485.pub2

Arvikar SL, Steere AC.Diagnosis and treatment of Lyme arthritis.Infect Dis Clin North Am. 2015;29(2):269-280. doi:10.1016/j.idc.2015.02.004

U.S. Food and Drug Administration.Combating antibiotic resistance.

Zagursky RJ, Pichichero ME.Cross-reactivity in β-lactam allergy.J Allergy Clin Immunol Pract. 2018;6(1):72-81.E1. doi:10.1016/j.jaip.2017.08.027

MedlinePlus.Bacterial infections.

Harvard Health Publishing.How to prevent infections.

MedlinePlus.Azithromycin.

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