Cephalexin Vs. Amoxicillin: All You Need To Know

Regarding bacterial infections, antibiotics are the standard treatment, with broad-spectrum antibiotics especially appealing because they can treat a range of infections. Amoxicillin and cephalexin are two examples of broad-spectrum antibiotics, and they are often used to treat similar bacterial infections, although there are some differences. 

Continue reading to learn more about cephalexin and amoxicillin, including their side effects, dosages, drug interactions, and why a doctor might choose to prescribe you one over the other.

Table of Contents

What Is Cephalexin?

Cephalexin belongs to the class of cephalosporin antibiotics, which treat bacterial infections by killing bacteria. Cephalexin fights bacterial infection by preventing bacteria from forming their cell walls. This makes it so the bacteria cannot grow and reproduce, and then they eventually die.

What Is Amoxicillin?

Amoxicillin is another antibiotic, and it belongs to the class of penicillin-like antibiotics. Like cephalexin, amoxicillin also fights bacterial infections by impeding the bacteria’s ability to form a cell wall.

Amoxicillin is one of the most commonly prescribed antibiotics of all time, with more than 50 million prescriptions for this medication filled each year.

Cephalexin vs Amoxicillin

Listed below is an in-depth comparison between cephalexin and amoxicillin to help you better understand when and why one medication might be used over the other. 

What Are Cephalexin and Amoxicillin Used For?

Despite both being antibiotics for bacterial infections, cephalexin and amoxicillin share some similarities and differences in the infections they treat.

Some bacterial infections that amoxicillin is commonly used to treat include:

  • bronchitis
  • pneumonia
  • infections of the nose, ears, urinary tract, throat, and skin
  • Lyme disease
  • stomach ulcers (due to H. pylori bacteria)

In some cases, amoxicillin may be paired with clavulanate potassium, which is effective in cases where bacteria are resistant to amoxicillin alone. This pairing is often used when treating skin, soft tissue, and urinary tract infections. 

Cephalexin, like amoxicillin, can also treat pneumonia and infections of the ears, urinary tract, and skin. In addition, cephalexin can treat certain respiratory tract infections and infections of the bone or genitals.

Cephalexin and amoxicillin may also be used to prevent endocarditis, an infection and inflammation of the lining of the heart valves.

Neither antibiotic will work on viral infections, such as the cold or flu, and taking antibiotics when they are not needed increases the risk of antibiotic resistance in a later infection.

Because there is a lot of overlap between what each medication treats, healthcare providers will typically choose the one that will be the most effective based on your medical history or other health-related factors. For example, your healthcare provider will likely prescribe cephalexin if you have a history of amoxicillin-resistant infections.

Side Effects of Cephalexin vs Amoxicillin Side Effects

Cephalexin and amoxicillin both share some side effects, which include:

Amoxicillin and cephalexin also have the potential for more severe side effects associated with an allergic reaction, such as:

  • skin blisters or peeling
  • rash
  • hives
  • itching
  • difficulty swallowing or breathing
  • wheezing
  • swelling of the throat, tongue, face, lips, or eyes
  • severe diarrhea

If you take amoxicillin or cephalexin and notice any of these symptoms, especially within one hour of taking the medication, seek immediate medical attention. 

Drug Interactions of Cephalexin vs Amoxicillin

When taking medication, it is always important to be aware of potential drug interactions, or how one drug may affect another. When two drugs are taken together, one might become less effective, or serious side effects may develop.

Both cephalexin and amoxicillin may interact with blood thinners, probenecid, and other antibiotics.

Additionally, cephalexin may interact with metformin, and amoxicillin may interact with allopurinol.

It is also essential to discuss the safety of taking amoxicillin or cephalexin with your doctor if you have kidney disease.

How To Use Amoxicillin or Cephalexin?

Cephalexin can be prescribed as a tablet, capsule, or suspension (liquid), which are all taken by mouth. Depending on your prescription, it may be taken every 6 or 12 hours with or without food, and the complete course typically lasts 1-2 weeks, depending on what condition is being treated.

The dosage prescribed for cephalexin will depend on your age and infection severity. Adults can be prescribed between 1-4 grams a day, which is divided between 2-4 doses. In comparison, children are prescribed medication doses based on their weight. A dose of 25-50 mg per kg of body weight is prescribed daily and divided into 2-4 doses.

Amoxicillin can come as a capsule, chewable tablet, tablet, or suspension (liquid), often taken every 8 or 12 hours, with or without food. For those taking the chewable tablets, they should be chewed completely before being swallowed, while the tablet and capsules should not be chewed or split at all.

The dosage of amoxicillin depends on your age and infection severity, and dosages often look as follows:

  • Adults with mild infections: 500 mg every 12 hours or 250 mg every 8 hours
  • Adults with severe infections: 875 mg every 12 hours or 500 mg every 8 hours.
  • Children with mild infections: 20-25 mg per kg of body weight per day, which is then divided into 2-3 doses
  • Children with severe infections: 40-45 mg per kg of body weight per day, divided into 2-3 doses.

These dosage ranges for cephalexin and amoxicillin are only general, and your doctor will prescribe the appropriate amount based on your age, infection severity, and medical history to effectively treat the infection.

For both medications, if you are taking the liquid form, it is important to shake it well before using it to ensure the medication is evenly distributed.

How Can DrHouse Help?

With DrHouse, you can meet with an online doctor in just 15 minutes to discuss your symptoms and receive a prescription. Your online doctor will consider your symptoms, health history, and other medications you take to decide between cephalexin, amoxicillin, or other antibiotics to effectively treat your infection and help you feel better.

Key Takeaways

Cephalexin and amoxicillin are two antibiotics with a significant number of similarities. They both destroy bacteria by affecting their cell wall, and they are used to treat a number of the same infections.

If you have had a previous instance of antibiotic resistance to either cephalexin or amoxicillin, the alternative antibiotic may be a more effective form of treatment for future infections. However, for both medications, it is essential to be aware of drug interactions to ensure that you are not taking something that would make your antibiotic less effective.

If you think you have an infection, an online doctor can evaluate your symptoms and prescribe an antibiotic such as cephalexin or amoxicillin. Your doctor will consider your age, infection severity, and other medical conditions to prescribe a dosage that will effectively cure the infection while minimizing the risk of unpleasant side effects.

References

  • Amoxicillin. (2020). In LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. National Institute of Diabetes and Digestive and Kidney Diseases. PMID: 31643176.
  • Sader, H. S., Jacobs, M. R., & Fritsche, T. R. (2007). Review of the spectrum and potency of orally administered cephalosporins and amoxicillin/clavulanate. Diagnostic microbiology and infectious disease, 57(3 Suppl), 5S–12S. https://doi.org/10.1016/j.diagmicrobio.2006.12.014 
  • Cephalexin: MedlinePlus Drug Information. (2022). https://medlineplus.gov/druginfo/meds/a682733.html 
  • Herman TF, Hashmi MF. Cephalexin. [Updated 2022 Feb 16]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK549780/ 
  • Ghafelehbashi, R., Akbarzadeh, I., Tavakkoli Yaraki, M., Lajevardi, A., Fatemizadeh, M., & Heidarpoor Saremi, L. (2019). Preparation, physicochemical properties, in vitro evaluation and release behavior of cephalexin-loaded niosomes. International Journal Of Pharmaceutics, 569, 118580. doi: https://www.doi.org/10.1016/j.ijpharm.2019.118580 
  • Akhavan BJ, Khanna NR, Vijhani P. Amoxicillin. [Updated 2021 Aug 17]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK482250/ 

DrHouse articles are written by MDs, NPs, nutritionists and other healthcare professionals. The contents of the DrHouse site are for informational purposes only and are not a substitute for professional medical advice, diagnosis, or treatment. If you are experiencing high fever (>103F/39.4C), shortness of breath, difficulty breathing, chest pain, heart palpitations, abnormal bruising, abnormal bleeding, extreme fatigue, dizziness, new weakness or paralysis, difficulty with speech, confusion, extreme pain in any body part, or inability to remain hydrated or keep down fluids or feel you may have any other life-threatening condition, please go to the emergency department or call 911 immediately.

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