Zithromax, known generically as azithromycin, is a cornerstone macrolide antibiotic in modern therapeutic regimens. It is distinguished by its advanced azalide structure, which confers a broad spectrum of activity against a wide array of gram-positive, gram-negative, and atypical pathogens. Its unique pharmacokinetic profile, characterized by extensive tissue penetration and a prolonged half-life, facilitates shorter, more convenient dosing schedules compared to traditional antibiotics, enhancing patient adherence and treatment success rates. This agent is a first-line choice for numerous community-acquired infections, offering clinicians a reliable and efficient tool for outpatient management.

Features

• Active pharmaceutical ingredient: Azithromycin (as azithromycin dihydrate)
• Standard dosage forms: Oral tablets (250 mg, 500 mg, 600 mg), oral suspension (100 mg/5mL, 200 mg/5mL), and intravenous solution for infusion
• Pharmacological class: Macrolide (azalide subclass) antibiotic
• Mechanism of Action: Binds to the 50S subunit of the bacterial ribosome, inhibiting RNA-dependent protein synthesis
• Spectrum of activity: Effective against susceptible strains of Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus, Moraxella catarrhalis, Chlamydia trachomatis, Mycoplasma pneumoniae, and Legionella pneumophila
• Unique pharmacokinetics: Demonstrates high tissue concentrations that can exceed plasma levels by 10- to 100-fold and an extended terminal elimination half-life of 68 hours, allowing for once-daily dosing

Benefits

• Convenient Dosing Regimen: The extended half-life often allows for a complete course of therapy to be administered in as few as 3 to 5 days, significantly improving patient compliance compared to antibiotics requiring multiple daily doses over a longer period.
• High Tissue Bioavailability: Achieves potent bactericidal concentrations directly at the site of infection, including lung tissue, genitourinary organs, and skin, leading to more targeted and effective eradication of pathogens.
• Broad-Spectrum Efficacy: Provides reliable coverage against a comprehensive range of common community-acquired bacterial and atypical pathogens, making it a versatile first-line or alternative treatment option.
• Established Safety Profile: As a widely prescribed antibiotic with decades of clinical use, its safety and tolerability are well-documented in both adult and pediatric populations (except in infants under 6 months for certain indications).
• Oral and IV Formulations: Availability in both oral and intravenous forms allows for seamless step-down therapy, enabling early hospital discharge and continuation of effective treatment in an outpatient setting.

Common use

Zithromax (azithromycin) is indicated for the treatment of patients with mild to moderate infections caused by susceptible strains of the designated microorganisms in the following conditions:

• Community-Acquired Pneumonia: Caused by Streptococcus pneumoniae, Haemophilus influenzae, Chlamydia pneumoniae, Mycoplasma pneumoniae, or Legionella pneumophila.
• Acute Bacterial Exacerbations of Chronic Obstructive Pulmonary Disease (COPD): Due to H. influenzae, M. catarrhalis, or S. pneumoniae.
• Acute Bacterial Sinusitis: Caused by H. influenzae, M. catarrhalis, or S. pneumoniae.
• Pharyngitis/Tonsillitis: Caused by Streptococcus pyogenes as an alternative to first-line penicillin therapy.
• Uncomplicated Skin and Skin Structure Infections: Caused by Staphylococcus aureus, Streptococcus pyogenes, or Streptococcus agalactiae.
• Urethritis and Cervicitis: For the treatment of non-gonococcal urethritis and cervicitis due to Chlamydia trachomatis.
• Genital Ulcer Disease: For the treatment of chancroid due to Haemophilus ducreyi.
• Mycobacterial Infections: Used as part of combination regimens for the prophylaxis and treatment of disseminated Mycobacterium avium complex (MAC) disease in patients with advanced HIV infection.

Dosage and direction

Administration is oral, with or without food. However, administration at least 1 hour before or 2 hours after a meal may increase absorption.

• Community-Acquired Pneumonia & COPD Exacerbations (Oral): 500 mg as a single dose on Day 1, followed by 250 mg once daily on Days 2 through 5. Total dose: 1.5 grams.
• Acute Bacterial Sinusitis (Oral): 500 mg once daily for 3 days.
• Pharyngitis/Tonsillitis (Oral): 500 mg as a single dose on Day 1, followed by 250 mg once daily on Days 2 through 5.
• Uncomplicated Skin/Skin Structure Infections (Oral): 500 mg as a single dose on Day 1, followed by 250 mg once daily on Days 2 through 5.
• Non-Gonococcal Urethritis/Cervicitis: A single 1 gram (1000 mg) oral dose.
• Genital Ulcer Disease (Chancroid): A single 1 gram (1000 mg) oral dose.
• Pediatric Dosing (Otitis Media, Community-Acquired Pneumonia): 10 mg/kg on Day 1 (not to exceed 500 mg), followed by 5 mg/kg on Days 2 through 5 (not to exceed 250 mg per day). Alternatively, 30 mg/kg may be given as a single dose (not to exceed 1500 mg).
• Mycobacterium avium complex (MAC) Prophylaxis: 1200 mg taken once weekly.
• Intravenous (IV) Dosing: Reserved for hospitalized patients with community-acquired pneumonia. 500 mg IV once daily for at least 2 days, followed by 500 mg orally once daily to complete a 7- to 10-day course.

Precautions

• Clostridium difficile-Associated Diarrhea (CDAD): Antibiotic use, including Zithromax, can cause overgrowth of C. difficile, potentially resulting in severe, persistent diarrhea. Evaluate if diarrhea occurs during or after therapy.
• Hepatotoxicity: Discontinue azithromycin immediately if signs and symptoms of hepatitis, such as fatigue, malaise, nausea, jaundice, or liver enzyme elevations, occur.
• Prolongation of QT Interval: Azithromycin has been associated with prolongation of the QT interval and rare cases of arrhythmias, including torsades de pointes. Avoid use in patients with known QT prolongation, history of torsades de pointes, uncorrected electrolyte imbalances, or clinically significant bradycardia, and in patients receiving Class IA or III antiarrhythmic agents.
• Exacerbation of Myasthenia Gravis: Has been associated with exacerbation of symptoms or new onset of myasthenia gravis.
• Infantile Hypertrophic Pyloric Stenosis (IHPS): Azithromycin use in neonates (treatment of pertussis) has been associated with IHPS. Weigh the benefits against the potential risks.
• Prescribing in the absence of a proven or strongly suspected bacterial infection is unlikely to provide benefit and increases the risk of developing drug-resistant bacteria.

Contraindications

Zithromax is contraindicated in patients with:

• A known history of hypersensitivity to azithromycin, any other macrolide or ketolide antibiotic (e.g., erythromycin, clarithromycin, telithromycin).
• A history of cholestatic jaundice/hepatic dysfunction associated with prior azithromycin use.

Possible side effect

The most common side effects are gastrointestinal in nature and are generally mild to moderate. Serious side effects are rare.

• Very Common (>10%): Diarrhea/loose stools, nausea, abdominal pain.
• Common (1-10%): Vomiting, dyspepsia, flatulence, headache, dizziness.
• Uncommon (0.1-1%): Rash, pruritus, vaginitis, taste perversion, elevated liver enzymes, photosensitivity.
• Rare (<0.1%): Angioedema, anaphylaxis, cholestatic jaundice, hepatitis, hepatic necrosis, hearing disturbances (including deafness), tinnitus, ventricular tachycardia (including torsades de pointes), QT prolongation, CDAD, neutropenia.

Drug interaction

• Nelfinavir: Coadministration significantly increases azithromycin serum levels. Monitor for known side effects of azithromycin, particularly hearing and liver-related effects.
• Warfarin: Potentiation of anticoagulant effect has been reported. Monitor prothrombin time (PT) and INR closely in patients receiving both drugs.
• Drugs that Prolong QT Interval: Concomitant use with other QT-prolonging agents (e.g., antipsychotics like pimozide, certain antidepressants, fluoroquinolones, antiarrhythmics like amiodarone, sotalol) may result in additive effects and increased risk of serious cardiac arrhythmias. Avoid concomitant use.
• Digoxin: Azithromycin may increase digoxin serum concentrations. Monitor digoxin levels.
• Antacids: Aluminum- and magnesium-containing antacids may reduce peak serum levels of azithromycin if administered simultaneously. Administer Zithromax at least 1 hour before or 2 hours after these antacids.

Missed dose

Take the missed dose as soon as you remember. If it is almost time for the next scheduled dose, skip the missed dose and resume the regular dosing schedule. Do not take a double dose to make up for a missed one.

Overdose

Symptoms of overdose are expected to be consistent with the drug’s adverse effect profile and may include severe nausea, vomiting, diarrhea, and transient hearing loss. There is no known specific antidote for azithromycin overdose. General supportive measures are indicated, with gastric lavage performed if ingestion was recent. All treatment should be symptomatic.

Storage

• Store Zithromax tablets and single-dose suspension packets at room temperature between 20°C to 25°C (68°F to 77°F).
• Store the constituted oral suspension (liquid) at room temperature (below 30°C/86°F) or under refrigeration (5°C/41°F). Discard any unused portion after the course of therapy is completed, or after 10 days, whichever comes first.
• Keep all medications out of the reach of children and pets.

Disclaimer

This information is for educational and informational purposes only and does not constitute medical advice. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any new treatment. Never disregard professional medical advice or delay in seeking it because of something you have read here. The information provided is based on the product’s prescribing information but may not be exhaustive.

Reviews

“Zithromax remains a workhorse in my infectious disease practice. The 5-day ‘Z-Pak’ regimen for community-acquired pneumonia and bronchitis offers unparalleled convenience and adherence rates. Its efficacy against atypicals is particularly valuable. I always remain vigilant for potential GI side effects and QT interactions in at-risk patients.” – Infectious Disease Specialist, 15 years experience.

“In pediatric otitis media and pneumonia, the short-course, once-daily dosing is a game-changer for parents and increases completion rates dramatically. The banana-flavored suspension is generally well-accepted. We carefully monitor for any signs of gastrointestinal upset.” – Pediatrician, 10 years experience.

“The single-dose therapy for chlamydial infections is a major public health advantage, ensuring effective treatment and reducing transmission. It simplifies partner treatment and follow-up. It’s a critical tool in our STI management protocols.” – Public Health Clinic Director.