Is Azithromycin a Good Alternative to Erythromycin?

Published February 15th, 2021 by Corey Riley
Fact Checked by
Camille Freking
Medically Reviewed:
Dr. Gerardo Sison
Updated Date: Jun 30th, 2022

Bacterial infections affect nearly everyone at some point in their lifetime, and these conditions are commonly treated with broad spectrum antibiotics like azithromycin and erythromycin.

Unfortunately, erythromycin in particular is associated with a number of uncomfortable side effects, including gastrointestinal distress, and interacts with a long list of medications.

Is azithromycin a good alternative to erythromycin?


Azithromycin and erythromycin are FDA-approved prescription medications that belong to a class of drugs called macrolide antibiotics.

Macrolide antibiotics work by i bacteria from producing certain proteins that are required for reproduction and survival.

Macrolide antibiotics in general are prescribed for the treatment of many different types of bacterial infections, but there are differences in the specific types of infections that are treated by azithromycin and erythromycin, as outlined below.

Azithromycin is sold under the brand name Zithromax, while erythromycin is known by the brand name Erythrocin.

Both act as a protein synthesis inhibitor and can be taken in an intravenous or intracellular format. However, both drugs are most commonly prescribed in their generic forms. 

Conditions Treated

Erythromycin and azithromycin are both used for the full eradication of certain bacterial infections in pediatric and adult applications. 

Erythromycin is most commonly used to treat certain bacterial infections and infectious diseases, including:

  • Bronchitis
  • Legionnaires’ disease
  • Pneumonia
  • Pertussis (whooping cough)
  • Diphtheria
  • Syphilis and other sexually transmitted diseases
  • Rheumatic fever
  • Ear infections
  • Intestinal infections
  • Gynecological infections
  • Urinary tract infections
  • Lower respiratory tract infections
  • Skin infections
  • Acne
  • Rosacea

Azithromycin is most commonly used for the treatment of the following:

  • Infections of the middle ear (otitis media)
  • Pneumonia
  • Mycoplasma pneumoniae
  • Laryngitis
  • Infections caused by Gram-negative pathogens
  • Sinusitis
  • Skin infections
  • Sexually transmitted diseases such as gonorrhea and chlamydia
  • Infections caused by Mycobacterium pneumoniae
  • Mycobacterial infections
  • Infections caused by Streptococcus pneumoniae
  • Infections caused by some strains of Staphylococcus aureus
  • Tonsillitis
  • Infections caused by Haemophilus influenzae

Both erythromycin and azithromycin are used to treat many different types of bacterial infections.

Although both drugs are considered equally effective for the treatment of many different bacterial infections, one drug may be more effective than the other for treating certain types of bacterial infections.

Standard Dosage and Length of Treatment

Azithromycin is most commonly prescribed in the form of a Z-pak. A Z-pak is a six-tablet prescription of azithromycin that instructs patients to take two tablets on the first day of treatment and one tablet each day for the next four days. Azithromycin can also be prescribed outside of a Z-pak depending on the condition being treated with the medication.

The typical dosing for adults of azithromycin is between 500 and 2000 mg, which is taken in single doses over the course of multiple days.

Erythromycin is most commonly prescribed in a dose ranging from 250 mg to 1,000 mg that is taken between two and four times per day. 

Children may take a lower dose or erythromycin. The medication is best taken with food, as it is known to cause an upset stomach but is less likely to do so when taken with a meal. 

In order to rid your system of the harmful bacteria that is causing your infection, antibiotics like azithromycin and erythromycin must be taken over a period of several days. 

Azithromycin has an average terminal half-life of 68 hours, while erythromycin has a half-life of approximately two hours.

The average course of treatment varies between three and ten days depending on the type of infection. However, it is common for patients to start to feel better before finishing their entire prescription, which can cause them to stop taking the drug prematurely.

When this occurs, the remaining bacteria in a patient’s body is able to adapt to the antibiotic, which can lead to antibiotic resistance. Therefore, it is important to finish your prescription of antibiotics even after you start to feel better.

Side Effects

Azithromycin and erythromycin both belong to the macrolide antibiotic class of medications and are known to cause similar common side effects.

However, azithromycin is known to have a much lower risk of causing gastrointestinal side effects than erythromycin and in general is better tolerated by most patients.

The two drugs differ in the types of serious and very serious side effects that are associated with each medication. Common side effects associated with azithromycin include:

  • Nausea
  • Diarrhea or loose stools
  • Abdominal pain
  • Vomiting

Less common side effects of azithromycin include:

  • Vaginitis
  • Indigestion or gastrointestinal problems
  • Rash
  • Ringing in the ears
  • Tongue discoloration
  • Muscle weakness

Rare but serious side effects of azithromycin include:

  • Angioedema
  • Cardiovascular issues including abnormal heartbeat or arrhythmia
  • Steven-Johnson Syndrome
  • Cholestatic jaundice
  • Serious allergic reactions
  • Abnormal liver tests

Common side effects of erythromycin include:  

  • Nausea
  • Diarrhea
  • Loss of appetite
  • Vomiting
  • Stomach pain or cramping

It’s important to tell your healthcare provider right away if you notice any serious side effects while being treated with erythromycin. Serious side effects associated with use of erythromycin include:

  • Liver disease, as evidenced by:
    • Yellowing eyes or skin
    • Severe stomach or abdominal pain
    • Persistent nausea or vomiting
    • Dark urine
  • Muscle weakness
  • Blurred vision
  • Hearing loss
  • Unusual tiredness
  • Trouble speaking
  • Drooping eyelids

Rare but very serious side effects of erythromycin require immediate medical attention. Very serious side effects associated with erythromycin include:

  • Severe dizziness
  • Fast or irregular heartbeat
  • Fainting

Azithromycin and erythromycin, like other antibiotics, both present a potential risk of causing the development of a dangerous condition called Clostridium difficile-associated diarrhea.

Clostridium difficile is a type of harmful bacteria that is known to cause inflammation in the colon, a condition called pseudomembranous colitis.

Patients who develop pseudomembranous colitis can experience symptoms ranging from mild diarrhea to severe inflammation. Left untreated, the condition can be severe.

People who are using azithromycin or erythromycin and who start to develop signs of pseudomembranous colitis, including diarrhea, abdominal pain, fever, and shock should contact a healthcare professional immediately. 

Azithromycin and erythromycin may cause other side effects in addition to those listed above. If side effects persist or worsen during or immediately after your treatment, consult your healthcare provider. 


As noted above, azithromycin is better tolerated than erythromycin by most patients, but how do the drugs compare in terms of effectiveness?

A study conducted in children between the ages of six months and 16 years of age with a cough illness that was either suspected to be or confirmed to be whooping cough (a type of cough caused by infection of a bacteria called Bordetella pertussis) found  that azithromycin was just as effective as erythromycin in treating whooping cough. 

Azithromycin is equally effective in the treatment of nongonococcal urethritis and cervicitis caused by the bacteria Chlamydia trachomatis.

Azithromycin also offers an equally effective treatment for gastroparesis compared to erythromycin but may provide relief for even longer than erythromycin.

Drug Interactions

Erythromycin is known to cause potentially dangerous interactions with many medications. Drug interactions associated with erythromycin include but are not limited to the following:

  • Amiodarone
  • Cisapride
  • Procainamide
  • Quinidine
  • Dofetilide
  • Pimozide
  • Propafenone
  • Sotalol
  • Itraconazole
  • Ketoconazole
  • Verapamil
  • Diltiazem
  • Phenytoin
  • Carbamazepine
  • Saquinavir
  • Quinupristin-dalfopristin
  • Bromocriptine
  • Triazolam
  • Midazolam
  • Ergotamine
  • Dihydroergotamine
  • Tadalafil
  • Sildenafil
  • Lovastatin
  • Simvastatin
  • Vinblastine

Azithromycin poses a much lower risk of drug interactions than erythromycin, which is one reason that azithromycin is often preferred for the treatment of many infections.

However, azithromycin is known to interact with the following medications:

  • Aluminum or magnesium-based antacids, including Maalox and Mylanta, which affect the body’s ability to absorb azithromycin. 
  • Amiodarone
  • Digoxin
  • Pimozide
  • Colchicine
  • Hydroxychloroquine
  • Phenytoin
  • Quinidine
  • Nelfinavir
  • Dofetilide

Consult a healthcare provider for other possible drug interactions associated with either drug.


Although azithromycin is commonly used for the treatment of some types of pneumonia, it should not be used to treat pneumonia in patients who have any of the following medical conditions:

  • Known or suspected bacteremia (bacteria in the blood)
  • Nosocomial (hospital-acquired) infections
  • Cystic fibrosis

Individuals who are currently hospitalized, do not have a spleen, are elderly or disabled, or have a compromised immune system should not be treated with azithromycin. 

Patients with any of the following medical conditions should speak to their doctor before using erythromycin.

  • Liver disease
  • Myasthenia gravis, a type of muscle disease
  • Kidney disease

Erythromycin is known to affect the heart and can potentially cause a condition called QT prolongation, a type of heart rhythm that is characterized by a fast and irregular heartbeat and symptoms such as fainting or severe dizziness.

Patients with a history of heart problems should discuss their medical history with their doctor before using erythromycin, as QT prolongation is serious and requires immediate medical attention.


Azithromycin presents a good alternative for erythromycin depending on the type of infection being treated with antibiotics.

Azithromycin has been shown to be equally effective in the treatment of many bacterial infections but is better tolerated than erythromycin, particularly in regards to the lower incidence of gastrointestinal side effects.

Other antibacterial and antimicrobial drugs that may help your condition include theophylline, clindamycin, clarithromycin, and penicillin.

Azithromycin is also less likely to cause drug interactions than erythromycin.

Although both medications are available in a generic form and are covered by most types of health insurance, it may be possible to save even more on your prescription by using a pharmacy discount card from USA Rx.

Research, Studies and Sources: