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Zithromax contains an active substance called Azithromycin. From the pharmacological aspect it belongs to a group of macrolide antibiotics, while it is chemically classified in the azalides. Zithromax exhibits a wide range of antibacterial effects and its mechanism of action is based on binding to the 50s subunit, which leads to the inhibition of bacterial protein synthesis, thus resulting in a bactericidal effect.

Zithromax is effective in the treatment of infections caused by the following microorganisms:

  • ​Haemophillus influenzae
  • ​Haemophillus parainfluenzae
  • ​Meticillin-sensitive Staphylococcus aureus
  • Penicillin-sensitive Streptococcus pneumoniae
  • Group A Streptococcus pyogenes
  • Moraxela catarrhalis
  • Legionella pneumophilia
  • Fusobacterium species
  • Pasteurella multocida
  • Prevotella species
  • Porphyromonas species
  • Chlamydia trachomatis

Azithromycin is not effective against enterococci, methicillin-resistant Staphylococcus aureus (MRSA) and Bacteroides fragilis.

Zithromax is metabolized in the liver and excreted through the bile.

General Info about Azithromycin


Zithromax Azithromycin is used in the treatment of the following infections:

  • ​Outpatient pneumonia, bronchitis, and acute exacerbations of chronic obstructive pulmonary disease
  • ​Pharyngitis, tonsillitis, and sinusitis
  • ​Otitis media
  • Soft tissue and skin infections, such as:
  1. Acne vulgaris
  2. Erythema migrans
  3. Erysipelas
  4. Ulcers and abscesses on skin
  • ​Uncomplicated genital infection caused by Chlamydia trachomatis

Many doctors do not recommend this drug to be used more than twice a year, because it may increase a risk of liver damage. You should always tell your doctor if you have recently used Zithromax.


Azithromycin is administered once a day, one hour before, or two hours after meals. In this way, the best bioavailability of the drug is achieved, which is in direct correlation with the efficacy of the medicine.

The usual dosage to Meds4sure Antibiotics: Zithromax Azithromycin 250mg & 500mg Dosage Tablets recommended by meds4sure is 500mg once daily for three days or 50mg on the day 1 of therapy, and 250mg from day 2 to day 5 of therapy.

The usual dose in the treatment of uncomplicated genital infections caused by Chlamydia trachomatis is 1000mg as a single dose. The usual dosage in patients who weigh less than 45 kg is 10mg/kg once daily for 3 days. You should swallow the tablet with sufficient amounts of water.

The dose should be reduced in patients with severe kidney damage.


Zithromax is contraindicated in patients who are allergic to the active substance Azithromycin or other macrolide antibiotics (Erythromycin and Clarithromycin). Like other antibiotics, Zithromax can also cause severe allergic reactions, including anaphylactic shock (occurring in less than 1 in 10,000 treated patients).

Since it is metabolized by the liver, Zithromax should not be used in patients who have severe liver damage, as significant increase in the blood levels may occur, thus leading to increased risk of adverse effects.

If you notice signs of liver damage such as asthenia, jaundice or dark color of the urine, the therapy should be stopped immediately. In addition, Azithromycin can cause damage to the liver and hepatic necrosis that may have a fatal outcome.

Clinical studies have not proven, but theoretically, the concomitant use of Zithromax with ergotamine derivatives (drugs used in the treatment of migraine) can lead to an ergotamine crisis that can have serious health consequences. For this reason, the use with ergotamine derivatives must be avoided.

All macrolide antibiotics, including Azithromycin, can cause prolonged heart repolarization and QT interval, which can lead to a severe arrhythmia called torsades de pointes. Therefore, Zithromax should not be used in patients who:

  • ​Take other medicines that can cause torsades de pointes
  • ​Have hypokalaemia
  • ​Have hypomagnesemia
  • Have slow heart rate
  • Have cardiac arrhythmias
  • Have severe heart failure

It has been demonstrated that the use of Zithromax in patients suffering from myasthenia gravis can aggravate the symptoms of this disease. For this reason, the drug must be very carefully used in patients with myasthenia gravis.

Azithromycin can disrupt the intestinal flora and cause diarrhea. Sometimes this diarrhea is caused by excessive reproduction of a bacterium called Clostridium difficile. This bacterium produces toxins that can affect your health. For this reason, it is important to contact your doctor if you notice any of the following symptoms:

  • ​Watery diarrhea
  • ​Presence of blood in the stool
  • ​Fever
  • Presence of mucus in the stool

Pregnancy and Breastfeeding

The FDA places this drug in Group B because animal studies have not shown that Zithromax is harmful to the fetus. However, this medicine should only be used during pregnancy only if clearly needed, as the safety of its use in pregnant women has not been established. It is now known whether Zithromax is excreted in breast milk, and therefore its use should be avoided during breastfeeding.

Side Effects

Zithromax can cause the following side effects:

  • ​Anorexia
  • ​Constipation
  • ​Pancreatitis
  • Fungal infection of the mouth
  • Flatulence
  • Dyspepsia
  • Vomiting
  • Pseudomembranous colitis
  • Change in the color of the tongue
  • Thrombocytopenia
  • Aggressive behavior
  • Anxiety
  • Loss of hearing
  • Interstitial nephritis
  • Acute renal failure
  • Vaginitis
  • Low blood pressure
  • Rapid heart rate
  • Torsades de pointes
  • Allergic reactions

Tell your doctor if you notice any side effects.


The concomitant use of Zithromax Azithromycin with the following medicines increases the risk of arrhythmias:

  • Anagrelid – a drug used in the treatment of an essential increase in the number of platelets in the blood.
  • Amiodarone, Sotalol, Ibutilide – antiarrhythmic drugs.
  • Efavirenz – a drug used to treat HIV.
  • Lumefantrine – a drug used to treat malaria.
  • Fluoroquinolone antibiotics, such as Ciprofloxacin, Norfloxacin, Moxifloxacin and others.
  • Bedaquiline – a drug used to treat tuberculosis.
  • Dolasetron – a drug used to prevent nausea that occurs after chemotherapy or radiation.
  • Bepridil – a drug used to treat angina pectoris.
  • Droperidol, Haloperidol and Clozapine – antipsychotics.
  • Escitalopram– a drug used to treat anxiety and depression.
  • Mifepristone – so-called abortion pill.

The concomitant use with the following drugs should also be avoided as it increases the risk of liver damage:

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    ​Leflunomide and Terflunomide – immunosuppressive drugs used in the treatment of psoriasis and rheumatoid arthritis.
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    ​Mipomersen – a drug used to treat high blood cholesterol levels.

It is not known whether alcohol increases blood levels of Zithromax, therefore the concomitant use with alcoholic beverages should be avoided.

Avoid grapefruit while taking Azithromycin, because it may increase the risk of Zithromax adverse effects.

(Last Updated On: November 11, 2020)

A Doctor of Public Health, Lacy Ryan has accrued more than ten years of experience, making a name for herself as a researcher, writer, policy analyst, and project manager specializing in public health and international development.She earned her PhD in Community and Behavioural Health at the Colorado School of Public Health, her Master’s Degree in Global Health and Public Policy at the University of Edinburgh, and her Bachelor’s Degree with Honours in Biomedical Sciences (with minours in Biology and Psychology) at the University of Waterloo.

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