Zithromax (Azithromycin)

What is Zithromax?

Zithromax (azithromycin) is a macrolide antibiotic with a broad spectrum of antibacterial activity and a distinct pharmacokinetic profile that allows single-dose or short-course treatment for several infections. It is approved by the European Medicines Agency (EMA) and is listed on the WHO Model List of Essential Medicines.

In sexual health, azithromycin is best known for its use as a single 1 g oral dose for the treatment of uncomplicated genital chlamydia and non-gonococcal urethritis. Its exceptional convenience — a single tablet taken once — makes it particularly valuable in settings where adherence to multi-day antibiotic courses is uncertain.

How does Zithromax work?

Azithromycin is an azalide (a subclass of macrolide) antibiotic that works by inhibiting bacterial protein synthesis:

• 50S ribosomal subunit binding: Azithromycin binds to the 50S ribosomal subunit of susceptible bacteria, the same target as other macrolides including erythromycin.
• Translocation inhibition: This binding prevents the translocation step of protein synthesis — the movement of the peptide chain from the A-site to the P-site of the ribosome — halting elongation of the growing protein chain.
• Bacteriostatic/bactericidal: Azithromycin is primarily bacteriostatic (inhibits growth) at standard concentrations but can be bactericidal against some organisms at higher concentrations.
• Intracellular accumulation: A particularly important feature of azithromycin is its remarkable ability to accumulate within cells, including phagocytic cells (macrophages, polymorphonuclear cells). This results in tissue concentrations 10–100 times higher than plasma concentrations, and intracellular concentrations that persist for days after dosing.

This intracellular accumulation explains two key clinical properties:

1. Efficacy against intracellular pathogens: Chlamydia trachomatis is an obligate intracellular pathogen — it lives and replicates inside host cells. Azithromycin’s high intracellular concentrations make it effective against this organism.
2. Single-dose efficacy: The prolonged intracellular half-life (tissue half-life of 2–4 days) means that therapeutic levels persist in tissues for 5–7 days after a single oral dose, providing ongoing antibacterial activity despite the drug having cleared from plasma.

Who is Zithromax for?

Primary sexual health indications:

• Chlamydia (Chlamydia trachomatis): 1 g single oral dose — first-line or alternative treatment (current European guidelines favour doxycycline as the preferred first-line, particularly for rectal chlamydia)
• Non-gonococcal urethritis (NGU): 1 g single oral dose — first-line treatment
• Mycoplasma genitalium (uncomplicated): 500 mg on day 1, then 250 mg on days 2–5 — though resistance is increasing
• Chancroid (Haemophilus ducreyi): 1 g single oral dose

Other uses:

• Respiratory tract infections
• Community-acquired pneumonia
• Alternative antibiotic for penicillin-allergic patients in appropriate indications

Zithromax is NOT appropriate for:

• Gonorrhoea (do not use as monotherapy — resistance is widespread in Europe)
• Patients with known macrolide allergy
• Patients with QT prolongation or on QT-prolonging medicines
• Patients with significant liver disease (azithromycin is hepatically processed)

Posología

Indication	Dose	Schedule
Chlamydia (uncomplicated genital)	1 g	Single dose
NGU	1 g	Single dose
Chancroid	1 g	Single dose
Mycoplasma genitalium (uncomplicated)	500 mg day 1, then 250 mg days 2–5	5 days total
Chlamydia (cervicitis, in pregnancy alternative)	1 g	Single dose

The 1 g dose can be taken as four 250 mg tablets or two 500 mg tablets simultaneously. Zithromax can be taken with or without food (food does not significantly affect absorption of the capsule/tablet formulation). Take with adequate water.

Efectos secundarios

Azithromycin is generally well tolerated, with a better gastrointestinal side effect profile than erythromycin.

Efectos secundarios frecuentes (afectan a entre 1 y 10 de cada 100 personas)

• Nausea
• Diarrhoea
• Abdominal pain
• Vomiting (less common than with erythromycin)
• Headache

Efectos secundarios poco frecuentes

• Flatulence
• Dyspepsia
• Dizziness
• Elevated liver enzymes
• Skin rash

Clinically important side effects

QT prolongation: Azithromycin prolongs the QT interval and can increase the risk of cardiac arrhythmias, including potentially fatal ventricular arrhythmias (torsades de pointes). The EMA has issued guidance on this risk. Risk is higher in patients who:

• Have known QT prolongation or hypokalemia
• Are taking other QT-prolonging medicines
• Have bradycardia or arrhythmias
• Have significant cardiovascular disease

Severe allergic reactions: Including angioedema, anaphylaxis, and Stevens-Johnson syndrome (rare)

Clostridioides difficile-associated diarrhoea: As with all antibiotics, disruption of gut flora can predispose to C. difficile overgrowth.

Hepatotoxicity: Severe liver reactions including cholestatic jaundice have been reported rarely.

Zithromax vs alternative antibiotics for chlamydia

Antibiotic	Dose	Duration	Efficacy (genital)	Notes
Doxycycline (preferred)	100 mg twice daily	7 days	~97–98%	Current preferred first-line
Zithromax (Azithromycin)	1 g single dose	1 day	~93–97%	Excellent adherence; single dose
Erythromycin	500 mg four times daily	7 days	~90–95%	Pregnancy alternative; poor GI tolerability
Amoxicillin	500 mg three times daily	7 days	~90%	Pregnancy alternative
Ofloxacin (Tarivid)	200–300 mg twice daily	7 days	~95%	Alternative; fluoroquinolone cautions

Current guideline position: The European STI guidelines (2015 and subsequent updates) and WHO guidelines both list azithromycin 1 g as an alternative first-line treatment for uncomplicated genital chlamydia. More recent evidence and meta-analyses have favoured doxycycline as the preferred choice due to higher cure rates particularly for rectal chlamydia infection. Azithromycin remains the preferred single-dose option and may be more appropriate where adherence to a 7-day course is a concern.

How to access Zithromax online in Europe

Zithromax (azithromycin) es un medicamento sujeto a prescripción médica en todos los estados miembros de la UE. No puede dispensarse legalmente sin una receta válida de un profesional médico autorizado.

Prescrivia opera como intermediario tecnológico: no prescribimos medicamentos, no empleamos médicos ni vendemos medicamentos. Nuestra plataforma conecta a los pacientes con médicos independientes registrados en la UE que pueden realizar evaluaciones de salud en línea confidenciales.

El proceso:

1. Complete una evaluación de salud: Describe your symptoms, any STI test results, relevant medical history, and any medications you take.
2. Revisión médica: Un médico independiente registrado en la UE revisa su evaluación. If azithromycin is clinically appropriate, they may issue a prescription.
3. Dispensación en farmacia: La receta se envía a una farmacia asociada autorizada de la UE para su dispensación y entrega directa.

Importante: Prescrivia no garantiza que se emita una receta. Todas las decisiones de prescripción son tomadas de forma independiente por profesionales médicos cualificados.

Información importante de seguridad

No tome Zithromax si usted:

• Are allergic to azithromycin or other macrolide antibiotics (e.g., erythromycin, clarithromycin)
• Have significant liver disease or hepatic dysfunction
• Are taking ergotamine or dihydroergotamine (risk of ergotism)

Informe a su médico antes de taking Zithromax si usted:

• Have a history of QT prolongation or cardiac arrhythmias
• Have hypokalaemia or hypomagnesaemia (electrolyte imbalances increase QT risk)
• Are taking other QT-prolonging medicines (antiarrhythmics, antipsychotics, certain antibiotics)
• Are taking warfarin (azithromycin may increase anticoagulant effect — INR monitoring advised)
• Are taking antacids containing aluminium or magnesium (take azithromycin at least 1 hour before or 2 hours after)
• Are pregnant or breastfeeding

Notificación a la pareja: If diagnosed with chlamydia or another STI, sexual partners from the preceding 6 months should be notified and offered testing and treatment to prevent reinfection and further transmission.

Fuentes

La información médica de esta página se basa en las siguientes fuentes:

• European Medicines Agency (EMA). Azithromycin — Summary of Product Characteristics. Disponible en: ema.europa.eu
• World Health Organization (WHO). WHO Guidelines for the Treatment of Chlamydia trachomatis. 2016. who.int
• World Health Organization (WHO). WHO Model List of Essential Medicines. 22nd edition, 2021.
• European STI Guidelines Editorial Board. 2015 European guideline on the management of Chlamydia trachomatis infections. Journal of the European Academy of Dermatology and Venereology.

Este contenido se revisa periódicamente para reflejar las directrices clínicas actualizadas. Se proporciona únicamente con fines informativos y no constituye asesoramiento médico. Consulte siempre a un profesional sanitario cualificado para obtener asesoramiento relevante para sus circunstancias de salud individuales.