Difference Between Azithromycin and Erythromycin

Edited by Diffzy | Updated on: August 09, 2022


Difference Between Azithromycin and Erythromycin Difference Between Azithromycin and Erythromycin

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Antibiotics are often prescribed drugs to treat different bacterial illnesses. Choosing the right bacteria pathogen is essential for effectively treating these diseases because there are millions of different varieties of bacteria. Particularly, macrolide antibiotics are a class of anti-infective drugs used to treat germs that typically affect the lungs, skin, or soft tissues. Additionally, they are highly successful in preventing STDs.The bacteriostatic antibiotics known as macrolides have a wide range of effectiveness against various gram-positive bacteria. Macrolides, which are now accessible, are well tolerated, ingested, and frequently used to treat mild-to-moderate infections. The liver damage caused by some macrolide antibiotics has been documented. Macrolides are, as their name implies, macrocyclic lactone rings that typically contain 12 or more atoms. Bacteriostatic medications are known as macrolide antibiotics typically contain one or more sugars, usually cladinose or desosamine.

The macrolides are a group of organic compounds that typically have one or more deoxy sugars, such as cladinose and desosamine, linked to a large macrocyclic lactone ring. Typically, the lactone rings have 14, 15, or 16 members. Macrolides are a subclass of natural compounds known as polyketides. Some macrolides are utilized as pharmaceuticals and have antibacterial or antifungal action. Macrolides are bacteriostatic because they slow down or prevent bacterial development rather than eliminate it. Any macrocyclic lactone with more than eight members is generally a contender for this class. The macrocycle may contain an oxazole ring, a thiazole ring, no nitrogen, amide nitrogen (but should be distinguished from cyclopeptides), or both. To distinguish from tannins, benzene rings are excluded from the analysis. As with the annamycin family, lactams rather than lactones are also prohibited. There are larger rings like those seen in tacrolimus as well as macrocycles with 12 to 16 members. Erythromycin, the first macrolide to be identified, was initially utilized in 1952. When a patient was allergic to penicillin or experienced a condition that was resistant to penicillin, erythromycin was frequently administered as a replacement. By chemically altering erythromycin, later macrolides were created, such as azithromycin and clarithromycin, which were intended to be more readily absorbed and to have fewer adverse effects (erythromycin caused gastrointestinal side effects in a significant proportion of users).

Mechanism of Action for Macrolides

The macrolides are inhibitors of protein synthesis. Inhibiting bacterial ribosomal translation and peptidyl transferase’s capacity to add the developing peptide connected to the tRNA to the following amino acid is assumed to be how macrolides work to prevent bacteria from producing proteins (similar to chloramphenicol). Another suggested cause is premature peptidyl-tRNA dissociation from the ribosome. To do this, macrolide antibiotics reversibly bind to the 50S subunit's P site on bacterial ribosomes. This conduct is thought to be bacteriostatic. Macrolides are concentrated by leukocytes and subsequently transported to the infection site.

The 23s ribosomal RNA molecule, among other ribosomal proteins, serves as a specific target for the macrolides' binding to the 50S ribosomal subunit. All macrolides prevent the production of bacterial proteins, however, they all work at various stages. The peptidyl transfer process is inhibited by 16-membered molecules, while the translocation of peptidyl-tRNA is blocked by 14-membered macrolides. According to the most recent theory, protein synthesis is inhibited by all macrolides because they cause peptidyl-tRNA to dissociate from ribosomes during the elongation phase.


Diseases brought on by Gram-positive bacteria (such as Streptococcus pneumonia) and a small number of Gram-negative bacteria (such as Bordetella pertussis, and Haemophilus influenza), as well as some infections of the respiratory tract and soft tissues, are treated with antibiotic macrolides. [3] Macrolides are frequently used as a penicillin alternative by patients since their antibacterial range is a little bit broader than that of penicillin. Macrolides are typically effective against beta-haemolytic streptococci, pneumococci, staphylococci, and enterococci. In contrast to penicillin, macrolides have been proven to be effective against chlamydia, mycoplasma, mycobacteria, Legionella pneumophila, and certain rickettsia.

Macrolides must not be administered to horses, rabbits, or other non-ruminant herbivores. They quickly generate a response that disrupts the digestive system fatally. Horses less than a year old can use it, but caution must be taken to prevent other horses (such as foal's mare) from coming into touch with the macrolide therapy. Macrolides can be given orally, topically, intravenously, orally, as tablets, capsules, solutions, or injections.


In tissues, macrolides are broadly dispersed and have concentrations that are similar to those in plasma or even greater in some cases. They build up inside numerous cells, such as macrophages, where their concentration may be 20 times higher than in the plasma. The dispersion of WBCs to the area of inflammation will thus be facilitated. This build-up contributes to the lengthy dosing interval that some macrolides have (e.g., tilmicosin). Spiramycin has particularly high tissue concentrations despite having relatively low plasma values. In the spleen, liver, kidneys, and particularly the lungs, macrolides tend to accumulate. They concentrate in the eye and permeate pleural and ascitic fluids, but they do not diffuse into the CSF or the eye (only 2%–13% of plasma concentration, unless the meninges are inflamed). They concentrate on milk and bile. Up to 75% of the dosage is bound by plasma proteins, who bind to 1-acid glycoproteins rather than albumin.

Azithromycin vs. Erythromycin

The macrolide antibiotics azithromycin and erythromycin are used to treat soft tissue infections, infections of the upper and lower respiratory tracts, and vaginal and urinary tract infections. A form of erythromycin is azithromycin. They differ in their mechanisms and times at which they take effect, nevertheless. The drugs the doctor prescribes could change depending on several factors.

The primary distinction between azithromycin and erythromycin is azithromycin's prolonged half-life. This could be a result of the drug's unusually broad tissue absorption and release. The human liver is primarily responsible for processing erythromycin. The majority of it is eliminated in the bile, while some also pass through the urine. Erythromycin has a half-life of about 1.5 hours. The effectiveness of birth control pills may be affected by either of these antibiotics.

Difference between Azithromycin and Erythromycin in Tabular Form                                                     

Table: Azithromycin vs. Erythromycin
Parameters of Comparison
Azithromycin, the generic name for Zithromax, is an antibiotic that is effective against several bacterial infections. However, it could also cause a rash, dizziness, or headaches.
 A variety of bacterial illnesses may be treated with Ery-Tab (erythromycin), an antibiotic. Check for drug interactions before usage.
Treats illnesses caused by bacteria.
Treatment and prevention of infections.
53 hours
2 hours
Negative Effects
Dosage Style
Oral tablet, oral powder, intravenous powder for injection.
Oral suspension, oral tablet, or oral capsule

What is Azithromycin?

The Croatian pharmaceutical company Pliva discovered azithromycin in 1980, and in 1988 the drug was given medical use approval under the brand name Sumamed. It is listed as one of the Essential Medicines by the World Health Organization. It is regarded by the World Health Organization as being of crucial importance to human medicine. It is a generic drug that is offered for sale in many different countries. With more than 15 million prescriptions written in 2019, it was the 48th most often prescribed drug in the US.

The medicine azithromycin is used to treat bacterial infections in the body. The microorganisms that are growing inside the human body will be eradicated. It is currently being studied after recently emerging as usually advantageous for the treatment of bacterial infections. You can use this medication if you have a sore throat. It mostly treats infections of the nose, throat, and lungs.

A specific type of antibiotic is azithromycin. It is frequently used to treat throat infections, various sexually transmitted diseases, and chest infections like pneumonia. Children's chest infections and ear infections are frequently treated with azithromycin. In patients who often contract infections, it can also be given over an extended period to prevent chest infections. On prescription, the drug is offered as capsules, pills, and a drinkable liquid. It can also be injected; however, this is often done in a medical facility. Azithromycin is also marketed under the name Zithromax. The usage of azithromycin is usually regarded as safe. However, unpleasant side effects like nausea, vomiting, stomach pain, or diarrhoea also occur. Hearing loss and enhanced bacterial resistance in isolates are both possible side effects of prolonged use of the medication. Although they are rare, allergic reactions are possible but unlikely. As a result, only those with a prescription can buy azithromycin. Additionally, it is used to treat travel-related diarrhoea and pneumonia. It is frequently used with other antimalarial drugs by doctors. It can be ingested or administered intravenously by injection.

Nausea, vomiting, diarrhoea, and upset stomach are typical side effects. It is possible to experience an allergic reaction, such as anaphylaxis, QT prolongation, or a specific type of diarrhoea brought on by Clostridium difficile. There has been no evidence of danger from using it while pregnant. Although its safety during breastfeeding has not been established, it is probably safe. An antibiotic is known as an azalide, or macrolide is azithromycin. It functions by reducing protein synthesis, which prevents bacterial growth.

What is Erythromycin?

The antibiotic erythromycin was initially discovered in the bacteria Saccharopolyspora erythraea in 1952. It is listed as one of the Essential Medicines by the World Health Organization. With more than two million prescriptions written, it was the 215th most often prescribed drug in the United States in 2017. A multitude of bacterial illnesses can be treated with the antibiotic erythromycin. This includes syphilis, pelvic inflammatory disease, chlamydia infections, skin infections, and respiratory tract and skin infections. Additionally, it can help with delayed stomach emptying and Group B streptococcal infection in the foetus when given during pregnancy. It can be administered orally and intravenously. After delivery, an eye ointment is typically advised to protect the newborn’s eyes against infections.

The main purpose of erythromycin is to treat infections brought on by penicillin resistance. It provides greater defence against upper respiratory tract infections. Erythromycin may be given to you by your doctor as pills, slow-release capsules, gels, ophthalmic solutions and ointments, and other dosage forms. The precise mechanism of action of erythromycin is uncertain. However, it is known that it might possess bactericidal qualities. Azithromycin functions by halting the development of bacteria inside the body. By interfering with their protein production, this is achieved. An antibiotic called erythromycin is used to treat a variety of bacterial diseases. Inhibiting the spread of germs is another application for it. The macrolide class of antibiotics includes the drug erythromycin. It functions by halting the spread of germs. This antibiotic is only used to treat or prevent bacterial diseases. Viral infections cannot be treated with it.

An antibiotic loses its potency for treating future illnesses when it is administered when it is not necessary. Erythromycin can be taken by adults, even those who are pregnant or nursing. Erythromycin can be taken by kids. Erythromycin should be avoided by some people. Erythromycin may cause nausea, vomiting, and stomach pain as adverse effects. Erythromycin in particular may not be suggested by the doctor as a first-line treatment as a result. Patients taking these medications may experience negative side effects like urticaria and anaphylaxis. In addition, erythromycin is used to prevent heart infections in patients undergoing dental or other surgical procedures.

Consequences like nausea, vomiting, and diarrhoea are common. More serious side effects include colitis caused by Clostridium difficile, problems with the liver, a protracted QT, and allergic reactions. It is usually safe in persons who are allergic to penicillin. Erythromycin also appears to be safe to take when pregnant. Although it is usually safe when breastfed, if the mother uses it within the first two weeks of a baby's life, the newborn may be more likely to develop pyloric stenosis. If the baby is given the drug at this age immediately, there is still a risk. It lowers bacterial protein synthesis and is a member of the macrolide class of antibiotics.

Difference Between Azithromycin and Erythromycin In Points

  • Azithromycin, the generic name for Zithromax, is an antibiotic that is effective against several bacterial infections. Ery-Tab (Erythromycin), on the other hand, is an antibiotic that may be used to treat a variety of bacterial infections; nevertheless, it may cause headaches, dizziness, or a rash. Check for drug interactions before usage.
  • While Erythromycin both prevents and treats infections, Azithromycin only treats bacterial infections.
  • The half-life of azithromycin is 53 hours while that of erythromycin is 2 hours.
  • Erythromycin has a lower frequency of side effects than Azithromycin, although the latter has a higher frequency.
  • In contrast to erythromycin, which comes in the dosage forms of oral capsule, oral tablet, and oral suspension, azithromycin is administered intravenously for injection, orally for reconstitution, and as an oral tablet.


Similar to erythromycin, but with a longer half-life, azithromycin stimulates antral activity. Azithromycin, on the other hand, has fewer drug-drug interactions than erythromycin, which makes it a promising new treatment choice for gastroparesis and gastrointestinal dysmotility. Both azithromycin and erythromycin may cause nausea, diarrhoea, vomiting, and stomach discomfort. As a result, particularly Erythromycin, your doctor might not suggest them as a first-line treatment. Patients taking these medications may experience negative side effects like urticaria and anaphylaxis.

Additionally, the usage of azithromycin as a first-line antibiotic for treating babies is expanding. Additionally, it is frequently used by people whose immune systems have been compromised for whatever cause. To treat infections, doctors recommend azithromycin and erythromycin. However, if you are expecting, your doctor might suggest taking azithromycin. Your doctor could choose azithromycin since it is simple to take (just one pill daily). Additionally, some people claim that compared to erythromycin, azithromycin has fewer adverse effects.



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"Difference Between Azithromycin and Erythromycin." Diffzy.com, 2023. Mon. 27 Mar. 2023. <https://www.diffzy.com/article/difference-between-azithromycin-and-erythromycin-813>.

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