Clarithromycin Vs Azithromycin


Bacterial infections such as pneumonia, bronchitis, and sexually transmitted diseases can be treated with the help of antibiotics such as Clarithromycin and Azithromycin. Infections occur when pathogens capable of causing disease invade our bodies through the eyes, nose, or other openings (such as wounds that breach the skin barrier).

The prevalence of tourism and international travel has further accelerated the risk of infection. It's easier for pathogens to spread from one corner of the world to another because every passenger traveling by aircraft is a potential carrier. However, the rise of Clarithromycin and Azithromycin has made it easier to treat infections and minimize complications in patients.

About Clarithromycin and Azithromycin

What is Clarithromycin?

Clarithromycin is a semisynthetic macrolide antibiotic that is used to treat a wide range of bacterial infections. This includes Lyme disease, skin infections, pneumonia, and strep throat. Clarithromycin works by inhibiting bacterial protein synthesis by binding to the 50s ribosomal subunit.

This binding restricts peptidyl transferase activity and disrupts the amino acid translocation during the protein assembly process. Clarithromycin has been derived from erythromycin and has a long serum half-life with superior tissue penetration. The antibiotic has a macrolide 14-membered lactone ring - which is the exact same as erythromycin; the only exception is that the methoxy group replaces the hydroxyl group at position six.

It is worth mentioning that Clarithromycin does not work against flu, colds, and other virus infections. Clarithromycin is only available with a valid prescription.

What conditions is Clarithromycin approved to treat?

Clarithromycin is used for treating a wide range of infections, such as pneumonia, cellulitis, stomach ulcers, bronchitis, and Lyme disease, among others. In other words, the antibiotic can treat any infection as long as it can disrupt the bacteria’s protein synthesis by impairing the elongation cycle of the peptidyl chain.

However, this antibiotic does not work against flu, colds, and other similar infections.

How does Clarithromycin work for Infections?

Clarithromycin works by killing bacteria or stopping their growth. Some people take medicine in the form of extended-release tablets, which means that it is slowly released into the body over the course of 24 hours. These tablets are taken once a day. Clarithromycin can treat most infections within the span of a few days.

It has a long serum half-life with superior tissue penetration, allowing multiple daily dosing to treat infections. Clarithromycin disrupts protein synthesis in bacteria by binding to subunit 50S of the bacterial ribosome. Moreover, it has a superior first-pass metabolism in the liver. Its main metabolites are 14-R-hydroxy CAM, 14-S-hydroxy CAM, and N-desmethyl CAM. Of these, 14-R-hydroxy CAM is responsible for the medication’s anti-bacterial effect.

Clarithromycin has an average half-life of 6 hours, with an oral dose of 500 mg taken every 12 hours. Using clarithromycin results in increased serum levels and potential increased toxicity of multiple drugs metabolized by these enzymes. This medication can also inhibit the metabolism of proteinase inhibitors.

What is Azithromycin?

Azithromycin is a macrolide class of antimicrobials that are used to treat a wide range of infections, including pneumonia, sinusitis, Lyme disease, and some sexually transmitted infections. Its mechanism of action includes the inhibition of proinflammatory cytokine production, inhibition of bacterial protein synthesis, and macrophage polarization alteration.

Azithromycin binds the bacterial 50S ribosomal subunit, which prevents bacterial protein synthesis. This allows the medication to stop the growth of various pathogens or outright kill them.

However, just like Clarithromycin, Azithromycin does not work for virus infections and colds. It is only available with a doctor’s prescription. The average terminal elimination half-life of Azithromycin is about threeand days.

What conditions is Azithromycin approved to treat?

Azithromycin is used to treat various infections caused by pathogens. It is often prescribed for treating bronchitis, pneumonia, STDs, and infections of the lungs, sinuses, skin, and ears. The macrolide may also be used for treating patients with a chronic wet cough. The good oral bioavailability and superior half-life of the medication allow it to be used in frequent doses, including once-daily and even once-to-three times weekly dosing.

Azithromycin has been shown to have in vitro antiviral properties, which has spiked interest in the experimental treatment of the coronavirus.

How does Azithromycin work for Infections?

Azithromycin works by killing pathogens or slowing down their growth. It binds to the 23S rRNA of the 50S ribosomal subunit of bacteria such as Chlamydia trachomatis and M. intracellular. This prevents protein synthesis of the bacteria, thereby killing them. It usually takes about seven days for Azithromycin to cure chlamydia in patients.

This mechanism of action will not work against colds, cases of flu, and other virus infections. Unlike erythromycin, Azithromycin is less prone to dissociation from the gram-negative ribosome, improving its efficiency against gram-negative pathogens. It can easily move from the bloodstream into tissues and readily penetrate cellular membranes, allowing it to be highly effective against intracellular pathogens.

Azithromycin is only available with a doctor’s prescription.


How effective are Clarithromycin and Azithromycin for treating Infection?

Both Clarithromycin and Azithromycin have been shown to be extremely effective at treating a wide range of bacterial infections. They start working soon after the patient takes their first dose. Note that oral forms of both Clarithromycin and Azithromycin usually require about 2 to 3 hours to reach a full concentration in the body, and the effects may not be noticeable right away. However, patients should start to feel better in a few days.

Both Clarithromycin and Azithromycin are highly effective against gram-positive and gram-negative bacteria (with a few exceptions, such as enterococci). They are especially effective against chlamydia, bordetella pertussis, legionella spp., and borrelia spp.

Dosage information

How is Clarithromycin administered for Infections?

Clarithromycin is administered orally. It comes in both tablet and liquid form - both of which are to be taken by mouth. The regular tablet and liquid may be taken with or without food at 12-hour intervals for up to 2 weeks. Most people will be asked to take the medication twice a day: once in the morning and once in the event.

It is common to take slow-release Clarithromycin tablets that are gradually released into the body over the course of 24 hours. These slow-release tablets are to be taken once a day. Patients may be prescribed Clarithromycin Infusions if they are unable to swallow Clarithromycin tablets or if they have severe infections. Clarithromycin infusion can be used on patients over the age of 12.

Side Effects

What are the most-common side effects of Clarithromycin?

The most common side effects of Clarithromycin include the following:

  • Diarrhea
  • Nausea
  • Stomach pain
  • Heartburn
  • Gas
  • Vomiting
  • Headache
  • Change in taste

Are there any potential serious side effects of Clarithromycin?

* If you experience any of these serious side effects, seek medical help immediately

  • Rash
  • Chest pain
  • Severe diarrhea with bloody stools
  • Hives
  • Itching
  • Swelling in the facial area, hands, feet, or ankles
  • Extreme lethargy
  • Unusual bruising or bleeding
  • Yellowing of the eyes
  • Difficulty swallowing or breathing
  • Fever
  • Loss of appetite
  • Dark colored urine
  • Double visions
  • Hallucinations (seeing or hearing things that are not there)
  • Irregular heartbeat
  • Muscle weakness

What are the most-common side effects of Azithromycin?

Here are the most common side effects of Azithromycin:

  • Nausea
  • Diarrhea
  • Vomiting
  • Loss of appetite
  • Headaches
  • Changes in taste
  • Fever
  • Swelling
  • Scaly skin
  • Blistering

Are there any potential serious side effects of Azithromycin?

* If you experience any of these serious side effects, seek medical help immediately

  • Blurred visions
  • Dizziness
  • Fainting
  • Lightheadedness
  • Confusion
  • Chest pain
  • Irregular heartbeat
  • Difficulty breathing
  • Extreme lethargy
  • Dark pee
  • The whites of the eye turning yellow
  • Tinnitus
  • Severe diarrhea that contains blood or mucus
  • Severe pain in the stomach (a sign of inflammation of the pancreas)

Contraindications and interactions

Warnings and general precautions for Clarithromycin and Azithromycin

The FDA has warned the public that taking Azithromycin can cause abnormal changes in the heart and could lead to fatal, irregular heart rhythm. Some patients are at a high risk of delivering this, including individuals with low blood levels of magnesium, existing QT interval prolongation, and a slower-than-normal heart rate. Consult your doctor if you are at risk of fatal heart rhythms before taking Azithromycin.

Taking Clarithromycin can cause severe skin reactions. This is why you should check in with your doctor if you notice peeling, blistering, or loosening of the skin.

Both Azithromycin and Clarithromycin can affect your heartbeat. This is why it is not recommended to take any other medicines that have the same effect. You should tell your doctor if you’re taking any medicines that can affect your heartbeat, including medication for irregular heartbeats, such as sotalol or amiodarone.

Contraindications and important interactions for Clarithromycin and Azithromycin



Clarithromycin isn’t suitable for everyone. You may not be prescribed the medication if you have the following:

  • Severe Hypersensitivity Reactions
  • Coronary heart disease
  • Had diarrhea when taking antibiotics
  • Rapid ventricular heartbeat
  • Diarrhea from an infection
  • Low amount of magnesium or potassium in the blood
  • Inflammation of the liver
  • Chronic kidney disease


Azithromycin isn’t suitable for everyone. You should report to your doctor if you have:

  • Heart problems
  • Liver and kidney problems
  • Myasthenia gravis
  • Diabetes
  • Toxoplasma Infections

Drug/Medication Interactions




3,5-diiodothyropropionic acid



  • Anagrelide
  • Arsenic trioxide
  • Artemether
  • Asenapine
  • Astemizole

Food/Beverage/Supplement Interactions


Food interactions

  • Spicy food
  • Grapefruit
  • Avoid chicken raised on antibiotics

Beverage interactions

  • Grapefruit juice

Supplement interactions

Check with your doctor before taking any supplements with Clarithromycin


Food interactions

  • High-acid fruits
  • Chocolate
  • Tomato
  • Anything with a high acid content

Beverage interactions

  • Citrus juice
  • Grape juice
  • Soda

Supplement interactions

Call your door before taking any supplements with Azithromycin

Cost Comparison

How much do Clarithromycin and Azithromycin cost?

The average price of Clarithromycin is north of $150 for a supply of 28 500 mg tablets, but some pharmacies may offer coupons and discounts. The cost of an azithromycin oral tablet 250 mg for a supply of 2 tablets is about $14. Both Clarithromycin and Azithromycin are covered by most Medicare and insurance plans.

Popularity of Clarithromycin and Azithromycin

Both Clarithromycin and Azithromycin are popular forms of antibiotics that are commonly prescribed to patients. There have been 275,000 prescriptions for Clarithromycin, according to ClinCac. The number of prescriptions for Azithromycin tablets has been over 10 million in 2020 alone. This makes it the most popular antibiotic in the US.



So there you have it, an in-depth comparison of Clarithromycin and Azithromycin. Both medications are very similar, with very few differences. Of these, Azithromycin is the most popular, with over 10 million precautions in the US alone, compared to just 275,000 prescriptions for Clarithromycin in 2020.

The side effect profile, as well as the efficacy of both medications, is very similar. In both cases, it is important to consult your doctor before changing your dose or discontinuing the medication. Always inform your doctor of changes in your symptoms and if you’re taking any other medications to prevent drug interactions.