Is Azithromycin a Penicillin?

Penicillin allergies result when your immune system adversely reacts to an antibiotic from the penicillin class. Some symptoms of a penicillin allergy include tightness in the throat, itching, rash, hives, swelling, wheezing, coughing, or difficulty breathing. 

Those with a penicillin allergy to one drug in this class have to be careful to avoid all other types of penicillin. As such, it’s common to wonder what drugs are penicillins. For example, is azithromycin, another commonly prescribed antibiotic, a penicillin?

Azithromycin is not a penicillin and is safe for those with a penicillin allergy to take. Continue reading to learn more. 

Table of Contents

Is Azithromycin a Penicillin?

Azithromycin is not a penicillin. 

Penicillins are a class of antibiotics containing medications derived from the Penicillium fungi. They were discovered by coincidence when the growth of Staphylococcus aureus bacteria on an uncovered petri dish was accidentally contaminated. The scientist, Alexander Fleming, noticed that the bacteria near the mold were dying, and thus, penicillin was discovered. 

Penicillins work by preventing the bacteria from creating a cell wall, which is their outer layer of protection. Penicillins prevent amino acid chains from cross-linking, building weak cell walls in the bacteria that can easily rupture. 

Some types of penicillins include:

  • amoxicillin
  • nafcillin
  • piperacillin
  • ampicillin
  • dicloxacillin
  • ticarcillin

While penicillins encompass many different medications, azithromycin is not one of them. However, azithromycin treats many of the same infections as penicillin, making it a suitable alternative if someone cannot take penicillin, such as for an allergy. 

Can You Take Azithromycin If You Are Allergic to Penicillin?

Azithromycin does not contain any penicillin, and a study on the safety of azithromycin in those with a penicillin allergy also found that there was no reaction to azithromycin. Based on these results, azithromycin is an alternative to penicillin for those with allergies. 

However, some people may be allergic to azithromycin, and an allergy to both penicillin and azithromycin is possible. If you ever notice signs of an allergic reaction while taking azithromycin, seek immediate medical attention. 

What Exactly Is Azithromycin?

Azithromycin belongs to the macrolide class of antibiotics. It fights bacterial infections by inhibiting bacterial protein synthesis. Proteins are crucial for bacterial survival, so without proteins, the bacteria die, and the body can clear out the infection. 

This means that azithromycin does not directly kill bacteria but instead slows or completely stops its growth. This treatment method allows azithromycin to be effective against many atypical bacteria, including chlamydiae and mycobacteria. 

The brand name of azithromycin is Zithromax, and it might also be known as a Z-Pak. It is available as regular and extended-release liquid or tablets. 

Some of the bacterial infections that azithromycin may be prescribed to treat include:

  • skin infections
  • pneumonia
  • syphilis
  • eye infections
  • Lyme disease
  • sinus infections
  • tonsillitis
  • urethritis

This list is incomplete, and azithromycin may be prescribed to treat something not included. 

What Are the Different Types of Penicillin?

There are four different types of penicillin. Three are purely penicillin, and the fourth category encompasses combination drugs that allow penicillin to be more effective. 

Natural Penicillins

The natural penicillins (penicillin G and V) are only effective against gram-positive bacteria.

Modern Semi-Synthetic Penicillins

Some examples of modern semi-synthetic penicillins include oxacillin and ampicillin. These varieties can be taken orally and have some resistance to beta-lactamase, which bacteria create to break penicillins down and make them less effective. Additionally, modern semi-synthetic penicillins are effective against gram-negative bacteria, which are notoriously more resistant to antibiotics. 

Antipseudomonal Penicillins

This category includes piperacillin and denotes penicillins with more activity against the difficult-to-treat gram-negative bacteria, including Enterococcus, Pseudomonas, and Klebsiella. These penicillins concentrate in the urine, which makes them helpful for urinary tract infections caused by certain bacteria.

Penicillin/Beta-Lactamase Inhibitor Combinations

Some bacteria produce beta-lactamase to break down penicillins, making the bacteria resistant to this type of antibiotic. However, some medication varieties combine penicillin with a beta-lactamase inhibitor, which is a class of medications that keep beta-lactamase from breaking down the penicillin, thus allowing it to continue working. 

Some penicillins commonly combined with beta-lactamase inhibitors are amoxicillin, piperacillin, and ampicillin. Common beta-lactamase inhibitors include clavulanate, tazobactam, and sulbactam.

Key Takeaways

Penicillins are a class of antibiotics used to treat bacterial infections. Still, allergies to this group of medications can occur, and those with allergies often look for antibiotics that are just as effective as penicillin but safe to take in those with a penicillin allergy. 

Azithromycin is one alternative. This antibiotic does not belong to the penicillin class; it is instead a macrolide antibiotic. In addition to not containing any penicillin, azithromycin has also been shown, through trials, to be safely tolerated by those with a penicillin allergy, making it a safe alternative for certain infections. 

The different types of penicillins include natural penicillins, modern semi-synthetic penicillins, antipseudomonal penicillins, and penicillin/beta-lactamase inhibitor combinations. Each of these types of penicillin targets different infection types and are most effective in different scenarios. 


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  • Patterson RA, Stankewicz HA. Penicillin Allergy. [Updated 2023 Jun 20]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from:
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Content on the DrHouse website is written by our medical content team and reviewed by qualified MDs, PhDs, NPs, and PharmDs. We follow strict content creation guidelines to ensure accurate medical information. However, this content is for informational purposes only and not a substitute for professional medical advice, diagnosis, or treatment. For more information read our medical disclaimer.

Always consult with your physician or other qualified health providers about medical concerns. Never disregard professional medical advice or delay seeking it based on what you read on this website.

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