Which is Better for Respiratory Infection: Amoxicillin or Cephalexin?

October 13, 2025 •

3 min read

The vast majority of acute respiratory infections, such as the common cold, are caused by viruses and do not require antibiotics. For bacterial respiratory infections that do require medication, understanding which is better for a respiratory infection, amoxicillin or cephalexin, is crucial for effective treatment and preventing antibiotic resistance.

Quick Summary

This article provides a comprehensive comparison of amoxicillin and cephalexin for treating bacterial respiratory infections. It covers their different drug classes, specific uses, suitability for conditions like sinusitis and bronchitis, and key factors like patient allergies and bacterial resistance.

Key Points

Drug Class Difference: Amoxicillin is a penicillin, while cephalexin is a cephalosporin, both part of the beta-lactam family but with different specific uses.
Not First-Line for All Respiratory Infections: Cephalexin is generally not a first-line choice for most respiratory infections like sinusitis or pneumonia due to its limited coverage compared to amoxicillin or broader spectrum options.
Amoxicillin for Common Respiratory Illnesses: Amoxicillin is a preferred first-line treatment for common bacterial ear, throat, and sinus infections when a penicillin allergy is not a factor.
Allergy Considerations: Cephalexin may be a suitable alternative for patients with a mild penicillin allergy, though a small risk of cross-reactivity exists.
Viral vs. Bacterial: Most acute respiratory infections are viral and do not require antibiotics at all, a critical point in preventing antibiotic resistance.
Infection-Specific Choice: The best antibiotic depends on the specific bacteria causing the infection; there is no universal 'better' option.
Prescription Needed: A healthcare professional must determine the correct antibiotic based on a proper diagnosis.

Comparing Amoxicillin and Cephalexin for Respiratory Infections

While both amoxicillin and cephalexin are antibiotics used to treat bacterial infections, they belong to different drug classes and have distinct uses. Amoxicillin is a penicillin-class antibiotic, while cephalexin is a first-generation cephalosporin. Both are part of the larger beta-lactam family, which works by disrupting the bacterial cell wall synthesis. Their effectiveness for respiratory infections depends on the specific bacteria. There is no single "better" option; the choice depends on the type of infection, patient history, and local resistance patterns.

Amoxicillin: A Penicillin-Class Antibiotic

Amoxicillin is a common first-line treatment for bacterial respiratory tract infections, effective against bacteria like Streptococcus pneumoniae and Haemophilus influenzae.

It is often prescribed for:

Acute Otitis Media (Middle Ear Infection).
Acute Bacterial Rhinosinusitis (Sinus Infection), sometimes with clavulanate.
Strep Throat (Pharyngitis).
Bacterial Bronchitis (when confirmed).

Cephalexin: A First-Generation Cephalosporin

Cephalexin primarily targets gram-positive bacteria and has a more limited role in respiratory infections compared to amoxicillin. It is not a first-line treatment for most common respiratory conditions.

Cephalexin is primarily used for:

Skin and Soft Tissue Infections.
Urinary Tract Infections (UTIs).
Strep Throat (Pharyngitis) as an alternative for mild penicillin allergy.
Bone and Joint Infections.

Comparison Table: Amoxicillin vs. Cephalexin


Feature	Amoxicillin (Penicillin)	Cephalexin (Cephalosporin)
Drug Class	Penicillin	First-Generation Cephalosporin
Primary Uses	Ear, nose, throat, lung infections; often first-line for respiratory infections.	Skin, bone, joint, and urinary tract infections; alternative for some respiratory infections.
Respiratory Suitability	High for common bacterial respiratory infections.	Lower for many respiratory infections; not first-line for pneumonia or sinusitis.
Penicillin Allergy	Not suitable for patients with any penicillin allergy.	Can be used as an alternative for patients with mild penicillin allergies (lower cross-reactivity risk).
Spectrum of Activity	Effective against typical respiratory bacteria, but can be susceptible to beta-lactamase resistance.	Primarily targets gram-positive bacteria; broader spectrum than penicillin, but still susceptible to resistance.
Formulations	Capsules, tablets, chewable tablets, and liquid suspensions.	Capsules, tablets, and liquid suspensions.

Which to Choose for Specific Respiratory Issues

The choice between antibiotics depends on the specific respiratory condition.

Bacterial Sinusitis (Rhinosinusitis)

Amoxicillin, often with clavulanate, is commonly recommended for bacterial sinus infections. Cephalexin is generally not recommended due to less effective coverage against common sinusitis bacteria. Alternatives for penicillin allergy exist.

Acute Bronchitis

Acute bronchitis is usually viral and doesn't need antibiotics. For rare bacterial cases, amoxicillin may be used, but cephalexin is not standard treatment.

Pneumonia

Cephalexin is not a typical first-line treatment for community-acquired pneumonia due to insufficient coverage. Amoxicillin or broader options like amoxicillin-clavulanate or macrolides are often preferred, depending on severity and setting.

Strep Throat (Pharyngitis)

Amoxicillin is the preferred first-line treatment for strep throat. Cephalexin is a suitable 10-day alternative for patients with a mild penicillin allergy, but not for severe allergies.

The Role of Antibiotic Resistance

Antibiotic resistance is a critical factor. Overuse contributes to bacteria becoming resistant. Narrow-spectrum antibiotics like amoxicillin are often preferred for simple infections to preserve broader-spectrum drugs. Using an antibiotic with an unnecessarily wide spectrum can increase resistance.

Conclusion

Choosing between amoxicillin and cephalexin for a respiratory infection requires a medical assessment of the specific infection, likely bacteria, patient allergies, and health. Amoxicillin is a common choice for many bacterial respiratory infections when penicillin allergy is absent. Cephalexin is often used for other infections or as an alternative for mild penicillin allergies. Always consult a healthcare provider for diagnosis and treatment to ensure effective and responsible antibiotic use.

For more information on antibiotic use guidelines, consult resources from the Centers for Disease Control and Prevention (CDC).

Frequently Asked Questions

Cephalexin is generally not recommended for sinus infections (rhinosinusitis). While it treats some bacterial infections, it does not have the optimal spectrum of activity against the bacteria most commonly responsible for sinusitis. Amoxicillin or amoxicillin/clavulanate are typically preferred as first-line treatments.

Neither antibiotic is universally more potent. Their effectiveness depends on the type of bacteria causing the infection. Amoxicillin is more effective for certain respiratory pathogens, while cephalexin is better for conditions like skin and bone infections. The correct dosage and appropriate antibiotic for the specific pathogen are what determine the success of the treatment.

For patients with a history of mild penicillin allergy, cephalexin can be used, but there is a small risk of cross-reactivity. It is crucial to inform your doctor about your allergy history. Cephalexin should not be used if you have a history of a severe, immediate allergic reaction to penicillin.

Most cases of acute bronchitis are caused by a virus and do not require antibiotics. Antibiotics are only effective against bacterial infections. Your doctor can determine if your bronchitis is bacterial based on the duration and severity of your symptoms.

Both are beta-lactam antibiotics that work by inhibiting the synthesis of the bacterial cell wall, which causes the bacteria to die. However, they bind to different penicillin-binding proteins within the cell wall, meaning they affect different types of bacteria more effectively.

Completing the entire prescribed course of antibiotics is essential to fully eradicate the infection. Stopping early can allow surviving bacteria to mutate and become resistant to the antibiotic, making future infections harder to treat.

The primary difference lies in their drug class and coverage. Amoxicillin is a penicillin-derivative, while cephalexin is a first-generation cephalosporin. While both target many gram-positive bacteria, amoxicillin has a more targeted spectrum for common respiratory pathogens, while cephalexin is often better for skin infections.