Clarithromycin and Erythromycin

Difference Between Clarithromycin and Erythromycin

Brief overview of Clarithromycin and Erythromycin

Clarithromycin and Erythromycin are both antibiotics that belong to the macrolide class of drugs. They are used to treat a variety of bacterial infections.

Clarithromycin is a broad-spectrum antibiotic commonly used to treat respiratory tract infections such as bronchitis and pneumonia, as well as skin and soft tissue infections. It is also effective against certain types of bacteria that cause stomach ulcers. Clarithromycin works by inhibiting the growth of bacteria and preventing them from producing essential proteins.

Erythromycin, the first macrolide antibiotic, is also effective against a wide range of bacterial infections. It is commonly used for respiratory tract infections, skin and soft tissue infections, as well as certain sexually transmitted infections like chlamydia. Erythromycin works in a similar way to clarithromycin, by inhibiting bacterial protein synthesis.


Clarithromycin belongs to the macrolide class of antibiotic medications and can effectively treat various bacterial infections. Its use has become widespread.

Clarithromycin works by inhibiting bacteria’s ability to produce essential proteins, thus stopping their proliferation and inhibiting further infection. As it works against multiple strains of bacteria, this treatment option makes itself suitable for respiratory tract infections like bronchitis and pneumonia as well as skin or soft tissue infections caused by susceptible organisms.

Figure 01: Clarithromycin

Clarithromycin may also be prescribed to treat certain bacteria associated with stomach ulcers, such as Helicobacter pylori. When combined with other medication (proton pump inhibitors for instance) this treatment approach can be highly successful.

Clarithromycin comes in various forms, such as tablets, extended-release tablets and oral suspension.

Dosage and duration depend upon both the nature of infection being treated as well as personal medical circumstances – dosage could include tablets taken orally at once as well as extended release tablets taken at different intervals throughout treatment duration if indicated; adverse side effects could include nausea, vomiting and diarrhea due to taking too many tablets at one time and failing to complete full course treatments as directed to ensure effective elimination.

It’s vitally important that individuals follow prescribed dosage in order for effective infection elimination!


Erythromycin can be described as an anti-biotic used to treat a variety of types of bacterial infections like respiratory tract infections, skin infections the chlamydia infection, as well as pelvic inflammation.

This medication is effective in pregnancy to avoid streptococcal infections of the Group B group for the infant and also to slow the process of emptying stomach. The ways to administer this medication include an intravenous injection or oral route.

The bioavailability for this medication could range from 30-65 percentage, depending upon the type of ester. The protein binding capacity of this medication is around 90 percent. The process of metabolism for erythromycin takes place within the liver. The half-life of elimination is approximately 1.5 hours. Its elimination occurs via the bile.

Figure 02: Erythromycin

Some frequent side effects from these, including abdominal cramps, nausea, and diarrhea. Some serious adverse effects include complications with liver function or prolonged QT as well as allergies. It is generally suitable for those who have an allergy to penicillin.

Difference Between Clarithromycin and Erythromycin

Clarithromycin & Erythromycin
Figure 03: Clarithromycin & Erythromycin

Clarithromycin and Erythromycin both belong to the macrolide antibiotic class.

There are some key distinctions between them that set each apart:

  1. Spectrum of activity: Clarithromycin’s spectrum of activity is wider compared to that of erythromycin; it can effectively tackle both Gram-positive and Gram-negative bacteria strains; while its Effectiveness against Gram-positive ones tends to be Superior.
  2. Pharmacokinetics: Clarithromycin outshines erythromycin when it comes to its pharmacokinetics; its better absorption from the digestive tract results in higher and more consistent levels in bloodstream while its variable absorption often causes side effects in some people.
  3. Resistance: Over time, certain bacteria have evolved resistance to erythromycin; clarithromycin was developed as an antibiotic remedy against some of this resistance and often shows promise against such organisms.
  4. Dosage Frequency: Clarithromycin should typically be taken once or twice daily while erythromycin requires more frequent dosage – generally three or four times each day – which could compromise patient compliance and convenience.
  5. Drug Interactions: Both antibiotics have the potential to interact with one or more other drugs; however, clarithromycin tends to have more significant interactions than others with certain statin drugs used for cholesterol management, potentially increasing risks and adverse side effects.

Comparison chart of Clarithromycin and Erythromycin

Aspect Clarithromycin Erythromycin
Drug Class Macrolide antibiotic Macrolide antibiotic
Mechanism of Action Inhibition of protein synthesis by binding to the 50S ribosomal subunit Inhibition of protein synthesis by binding to the 50S ribosomal subunit
Indications Respiratory tract infections, skin infections, certain sexually transmitted diseases Respiratory tract infections, skin infections, certain sexually transmitted diseases
Spectrum of Activity Effective against gram-positive bacteria; active against some gram-negative bacteria Effective against gram-positive bacteria; limited activity against gram-negative bacteria
Pharmacokinetics Better oral bioavailability; longer half-life; extensive liver metabolism Variable oral bioavailability; shorter half-life; extensive liver metabolism
Common Adverse Effects Gastrointestinal disturbances (nausea, vomiting, diarrhea); reversible liver enzyme elevations; allergic reactions Gastrointestinal disturbances (nausea, vomiting, diarrhea); reversible liver enzyme elevations; allergic reactions
Preferred Use Often considered a second-line or alternative option when erythromycin is not effective or tolerated Less commonly used due to limited activity and potential for drug interactions


Clarithromycin and Erythromycin are both macrolide antibiotics used to treat bacterial infections. There are important differences between them. Clarithromycin has a broader spectrum of activity, improved pharmacokinetics, and is often effective against erythromycin-resistant bacteria.

It is generally better tolerated and requires less frequent dosing. On the other hand, erythromycin is more effective against Gram-positive bacteria and has a longer history of use. The choice between the two depends on factors such as the specific infection, bacterial susceptibility, and individual patient considerations.

It is essential to follow the guidance of a healthcare provider when determining the appropriate antibiotic treatment.