Why Azithromycin Is Given For 3 Days Only

In this blog, we will take a close look at the question of why azithromycin is usually given as a treatment for only 3 days. We will understand how the unique pharmacokinetic properties and high tissue selectivity of azithromycin make this possible. We will also analyze its effectiveness in treating various infections and the potential side effects associated with its use.
Jakub Gwiazdecki

Jakub Gwiazdecki

Fifth year medical student at the Medical Faculty of Comenius University in Bratislava.

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Why is Azithromycin given for 3 days only?

Azithromycin is a type of antibiotic that is often prescribed for a short course of three days. One reason why it is possible is that azithromicyn has a long elimination half-life. It takes around 68 hours for the elimination of half of the dosage [1].

This means that after two and a half days after the last dose, there is still more than half of the concentration in the organism left. The available drug concentration continues to fight the infection [1, 2].

Another property of azithromycin that allows it to be given for only 3 days is its high tissue selectivity. After absorption, it concentrates in cells of the immune system. It can be found in white blood cells like leukocytes, monocytes, and macrophages [3].

When an infection is triggered, the immune cells containing azithromycin migrate to the affected site. They act as natural transporters, and the drug is delivered straight to the infection site [1].

Is a 3 day Treatment with Azithromycin Effective?

Clinical trials have shown that a 3-day treatment with azithromycin is not as effective as a longer treatment with other antibiotics. It was concluded in the treatment of skin, respiratory tract, and soft tissue infections [3, 4].

However, in respiratory infections, a study showed better results when the infection was treated with azithromycin. After the 3-day treatment regime, approximately 98% of the infection resolved. When other antibiotics were given for 10 days, the resolution rate was only 87% [5].

Additionally, short-term treatment has other benefits. Patients adhere more frequently to short-term therapies than to long-term ones. It is more convenient for the patient, and it reduces the side effects linked with long-term treatment with antibiotics [3, 6].

What is Azithromycin?

Azithromycin belongs to the broad-spectrum macrolide antibiotic family. It is a derivative of erythromycin A, also a macrolide. It is created by a conversion process that includes the incorporation of a methyl-substituted nitrogen atom into a lactone ring. This creates a macrolide ring made of 15 members [7, 8, 9, 10].

Azithromycin is primarily used for the treatment of respiratory, enteric, and genitourinary infections. Also, it can be used for some sexually transmitted diseases [9]. Examples of the conditions for which azithromycin is commonly prescribed include middle ear infections, strep throat, pneumonia, typhoid, bronchitis, and sinusitis [11].

Aside from its antibacterial properties, azithromycin is also an immunomodulator. This has been used in chronic respiratory inflammatory diseases [9]. One of the recent uses was during the COVID-19 pandemic. Azithromycin was given to modulate the severe immune responses to the SARS-CoV-2 virus [12, 13].

What is Azithromycin Used For?

Azithromycin is administered for a variety of bacterial infections. It shows high effectiveness against respiratory tract infections. Particularly those caused by Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis can be well treated with azithromycin [14, 15, 3].

However, this macrolide is also used in skin and soft tissue infections and some sexually transmitted diseases [16, 9]. It is active against atypical organisms such as Chlamydia and Mycobacterium [16].

Because of its immunomodulatory effects, it can be used in chronic inflammatory disorders. These include diffuse panbronchiolitis, post-transplant bronchiolitis, and rosacea [17].

What are the Risk Factors and Side Effects of Azithromycin?

Generally, azithromycin is well-tolerated and considered safe for all patients [18]. Nevertheless, it can cause several side effects. The most common ones include:

  • diarrhea
  • stomach pain
  • nausea
  • vomiting
  • and headache.

These side effects are reported by around 4% of adults and 3% of children [18].

Less common adverse reactions include:

  • allergic reactions (skin rash and swelling of the tongue or lips),
  • arrhythmias,
  • severe diarrhea,
  • and coagulation disturbance (easy bleeding)[19].

Azithromycin is hepatotoxic, and because of that, it can cause liver problems. It can manifest with fatigue, pain in the abdomen, jaundice, and a dark urine color [20]. In severe cases, liver toxicity can lead to hepatic encephalopathy [21].

This microlite can also have some more serious cardiac side effects. It can lead to QT interval prolongation [20]. This condition is a predisposing factor for arrhythmia development, especially re-entry tachycardias. These fast heartbeats can be very dangerous and even lethal.

In addition, azithromycin can cause aphthous stomatitis [22] and is ototoxic, which can lead to impaired hearing [23].

Long-term use of azithromycin or any other antibiotic can lead to the development of bacterial resistance. The risk of resistance to this macrolide in acute therapies is low, as it is used for a short time. However, in patients treated for chronic inflammatory lung diseases, the risk of bacterial resistance increases 2.7-fold [23].

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Jakub Gwiazdecki

Jakub Gwiazdecki

Jakub is in his fifth year as a medical student at Comenius University in Bratislava, Slovakia. He has special interested in cardiology and in patient-centered medicine. His love for heart health isn't just book-smarts; he wants to know how it works, what it means for our feelings, and how key it is for health and happiness. Jakub thinks real good health care comes from always putting the patient at the centre, treating each person as a whole.