Maxithro (azithromycin): Uses, Dosage & Side Effects

What it's for (Indications)

Azithromycin is a macrolide antibiotic indicated for the treatment of mild to moderate infections caused by susceptible strains of the designated microorganisms.
These indications include, but are not limited to, acute bacterial exacerbations of chronic bronchitis caused by *Haemophilus influenzae*, *Moraxella catarrhalis*, or *Streptococcus pneumoniae*; community-acquired pneumonia caused by *Chlamydophila pneumoniae*, *Haemophilus influenzae*, *Mycoplasma pneumoniae*, or *Streptococcus pneumoniae*; pharyngitis/tonsillitis caused by *Streptococcus pyogenes* (as an alternative to first-line therapy in individuals who cannot use first-line therapy); uncomplicated skin and skin structure infections caused by *Staphylococcus aureus*, *Streptococcus pyogenes*, or *Streptococcus agalactiae*; urethritis and cervicitis due to *Chlamydia trachomatis* or *Neisseria gonorrhoeae*; and chancroid due to *Haemophilus ducreyi*.
It is also used in the treatment of acute otitis media caused by *Haemophilus influenzae*, *Moraxella catarrhalis*, or *Streptococcus pneumoniae*.
The selection of azithromycin should consider local susceptibility patterns and clinical guidelines to ensure appropriate antimicrobial stewardship and efficacy.

Dosage Information

Type	Guideline
Standard	The dosage of azithromycin varies significantly based on the type and severity of infection, as well as patient age and weight. For adults with community-acquired pneumonia, pharyngitis/tonsillitis, or acute bacterial exacerbations of chronic bronchitis, a common regimen is 500 mg orally as a single dose on Day 1, followed by 250 mg once daily on Days 2 through 5. Alternatively, for these indications, a 500 mg once-daily regimen for 3 days may be prescribed. For uncomplicated urethritis or cervicitis due to Chlamydia trachomatis, a single oral dose of 1 gram is typically administered. For uncomplicated skin and skin structure infections, the dosage usually follows the 5-day regimen. Pediatric dosing is weight-based, for example, 10 mg/kg orally once daily for 3 days for acute otitis media or 12 mg/kg once daily for 5 days for pharyngitis/tonsillitis, with specific maximum doses. Tablets may be taken with or without food, while the oral suspension generally provides better absorption when taken on an empty stomach, although some formulations permit administration with food. Adherence to the prescribed regimen is critical to achieve optimal therapeutic outcomes and minimize the development of antibiotic resistance.

Type

Guideline

Standard

The dosage of azithromycin varies significantly based on the type and severity of infection, as well as patient age and weight. For adults with community-acquired pneumonia, pharyngitis/tonsillitis, or acute bacterial exacerbations of chronic bronchitis, a common regimen is 500 mg orally as a single dose on Day 1, followed by 250 mg once daily on Days 2 through 5. Alternatively, for these indications, a 500 mg once-daily regimen for 3 days may be prescribed. For uncomplicated urethritis or cervicitis due to *Chlamydia trachomatis*, a single oral dose of 1 gram is typically administered. For uncomplicated skin and skin structure infections, the dosage usually follows the 5-day regimen. Pediatric dosing is weight-based, for example, 10 mg/kg orally once daily for 3 days for acute otitis media or 12 mg/kg once daily for 5 days for pharyngitis/tonsillitis, with specific maximum doses. Tablets may be taken with or without food, while the oral suspension generally provides better absorption when taken on an empty stomach, although some formulations permit administration with food. Adherence to the prescribed regimen is critical to achieve optimal therapeutic outcomes and minimize the development of antibiotic resistance.

Safety & Warnings

Common Side Effects

Azithromycin is generally well-tolerated, but like all medications, it can cause adverse effects.
The most frequently reported side effects are gastrointestinal in nature, including diarrhea, nausea, abdominal pain, and vomiting.
These are usually mild to moderate and transient.
Less common but more serious side effects include cardiovascular events, particularly QT interval prolongation, which can lead to life-threatening arrhythmias such as Torsades de Pointes, especially in patients with pre-existing risk factors.
Hepatic dysfunction, including elevated liver enzymes, hepatitis, and cholestatic jaundice, has been reported, with rare cases of hepatic necrosis and liver failure.
Hypersensitivity reactions can range from rash and urticaria to severe and potentially fatal conditions like Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), acute generalized exanthematous pustulosis (AGEP), and Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) syndrome.
*Clostridioides difficile*-associated diarrhea (CDAD) can occur, ranging from mild diarrhea to fatal colitis.
Other reported side effects include headache, dizziness, taste perversion, and candidiasis.
Patients should be advised to seek immediate medical attention for any severe or persistent adverse reactions.

Serious Warnings

Black Box Warning: Azithromycin does *not* carry an FDA-mandated Black Box Warning. However, it is associated with several serious and potentially life-threatening risks that warrant careful consideration and are critically important for patient safety. These serious warnings include the risk of **QT interval prolongation**, which can lead to ventricular arrhythmias, including Torsades de Pointes, especially in patients with pre-existing risk factors such as known QT prolongation, uncorrected hypokalemia or hypomagnesemia, clinically significant bradycardia, or concomitant use of other QT-prolonging drugs. Patients with these risk factors should be closely monitored or an alternative antibiotic considered. Furthermore, azithromycin has been associated with severe and sometimes fatal **hepatotoxicity**, including cholestatic jaundice, hepatic necrosis, and liver failure. Patients should be advised to seek immediate medical attention if signs or symptoms of liver dysfunction occur. Severe **hypersensitivity reactions**, including anaphylaxis, Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) syndrome, have been reported, with some cases being fatal and potentially recurring after initial symptomatic treatment. Finally, **Clostridioides difficile-associated diarrhea (CDAD)** has been reported with azithromycin use and can range from mild diarrhea to fatal colitis, necessitating careful evaluation of patients presenting with diarrhea after antibiotic therapy. While not a formal black box, these serious adverse events underscore the importance of careful patient selection, monitoring, and immediate discontinuation if such reactions develop.
Azithromycin carries several important warnings.
It should be used with caution in patients with known QT prolongation, a history of Torsades de Pointes, congenital long QT syndrome, bradyarrhythmias, or uncompensated heart failure, due to the risk of further QT interval prolongation and ventricular arrhythmias.
Concomitant use with other drugs known to prolong the QT interval (e.
g.
, antiarrhythmics, antipsychotics) should be avoided or carefully monitored.
Cases of fatal hepatic failure have been reported; azithromycin should be discontinued immediately if signs and symptoms of hepatitis occur.
*Clostridioides difficile*-associated diarrhea (CDAD) has been reported with nearly all antibacterial agents, including azithromycin, and its severity can range from mild diarrhea to fatal colitis.
Patients presenting with diarrhea after antibiotic use should be evaluated for CDAD.
Severe hypersensitivity reactions, including anaphylaxis, SJS, TEN, DRESS, and AGEP, have occurred.
These reactions can be life-threatening and may recur after symptomatic therapy has been discontinued.
Azithromycin should not be used in patients with pneumonia who are judged to be inappropriate for oral therapy due to moderate to severe illness or risk factors.
Exacerbation of symptoms of myasthenia gravis has been reported in patients receiving azithromycin therapy.
Infantile hypertrophic pyloric stenosis (IHPS) has occurred in neonates receiving azithromycin.
Prescribers should be vigilant for signs of new infections, as azithromycin use can lead to the overgrowth of non-susceptible organisms.

How it Works (Mechanism of Action)

Azithromycin exerts its antibacterial action by inhibiting bacterial protein synthesis. It achieves this by binding reversibly to the 50S ribosomal subunit of susceptible microorganisms. This binding site is located near the peptidyl transferase center, and azithromycin effectively blocks the translocation step in protein synthesis, thereby preventing the elongation of the peptide chain. This mechanism of action is generally bacteriostatic, meaning it inhibits bacterial growth and reproduction, but it can be bactericidal at higher concentrations against certain susceptible pathogens. As a macrolide, azithromycin exhibits a broad spectrum of activity against many Gram-positive and Gram-negative bacteria, as well as atypical organisms such as *Chlamydia* and *Mycoplasma*. Its unique pharmacokinetic properties, including rapid tissue penetration, high intracellular concentration in phagocytes, and a prolonged half-life, contribute to its efficacy and allow for shorter treatment courses and once-daily dosing for many infections. These properties enable sustained drug levels at the site of infection.