What should be the azithromycin dosage?

Posted on  December 28, 2020, Edited by Jason, Category  

What is azithromycin?

1. Definition

Azithromycin is a macrolide antibiotic. It was discovered in 1980 and launched in 1981. Its trade names are Tellite, Xishumei, and Shumei Te. Azithromycin is a semi-synthetic 15-membered macrolide antibiotic. Azithromycin is widely used, but you need to pay attention to azithromycin dosage, usage and side effects. BALLYAcan do macrolides test to let you know if there are macrolides residues in the milk you drink in 10min.

2. Azithromycin Indications

It is suitable for the following infections caused by sensitive bacteria: bronchitis, pneumonia and other lower respiratory tract infections; skin and soft tissue infections; acute otitis media; upper respiratory tract infections such as sinusitis, pharyngitis, tonsillitis, etc. (penicillin is a commonly used drug for the treatment of Streptococcus pyogenes pharyngitis, and also a commonly used drug to prevent rheumatic fever. Azithromycin can effectively eliminate oropharyngeal streptococci, but there is no data on the efficacy of azithromycin in the treatment and prevention of rheumatic fever).

Azithromycin is used for simple genital infections caused by Chlamydia trachomatis in sexually transmitted diseases of men and women. Azithromycin can also be used for simple genital infections caused by non-multi-drug resistant Neisseria gonorrhoeae and chancroid caused by Haemophilus duke (need to rule out co-infection of Treponema pallidum).

Azithromycin is suitable for community-acquired pneumonia caused by Chlamydia pneumoniae, Haemophilus influenzae, Legionella pneumophila, Moraxella catarrhalis, Staphylococcus aureus or Streptococcus pneumoniae, which requires intravenous drip treatment first, and pelvic inflammatory disease caused by Chlamydia trachomatis, Gonorrhoeae, Mycoplasma hominis that requires intravenous drip treatment first. If anaerobic infection is suspected, antibiotics against anaerobic bacteria should be used in combination.

3. Pharmacokinetics

This product is stable to gastric acid. Although the oral bioavailability is only 37% and the peak plasma concentration is about 0.4μg/ml after a single dose of 0.5g in 2 to 3 hours, the tissue distribution is good and the protein binding rate is low (7% to 23%), the eliminated half-life is 12 to 14 hours, and the concentrations in prostate, tonsils, lung tissue, stomach tissue, and female genital tissues reach 2.6 μg/g, 4.5 μg/g, 3.6 μg/g, 6.1 μg /g and 2.7~3.5μg/g respectively in 12 to 30 hours after taking the medicine.

More than 50% of the drugs are excreted by bile in their original form, and some are demethylated metabolites. The drug stays in the tissue for a long time and the release is slow. After a single dose is taken 14 days, the original drug can still be detected in the urine. The urinary excretion rate within 1 week is less than 6%, and the renal clearance rate is 1.67~3.156ml/s. The reason why the concentration of this product in the tissue is significantly higher than the blood concentration of the drug is mainly due to the active movement of the drug from local tissues to the above cells through neutrophils and phagocytes. Neutrophils that store drugs at the site of infection are stimulated by bacteria to release drugs and play an antibacterial effect.

Azithromycin dosage and usage


It is administered orally once a day, swallowed whole, and can be taken with food. Azithromycin tablets are used to treat various infectious diseases. The course of treatment and the method of use are as follows: For sexually transmitted diseases caused by Chlamydia trachomatis, Haemophilus duke or Neisseria gonorrhoeae, only a single oral administration of 1000 mg of this product is required. Treatment of other infections: The total dose is 1500 mg, 500 mg of this product is taken once a day for three days. Or the total dose is the same, 500 mg on the first day, 250 mg orally once a day on the 2nd to 5th day.

Take this product at least 1h before eating, or 2h after eating. Adults take 0.3g daily, 1 meal for 3 days; or 0.5g for the first dose, 0.1g daily for the next 5 days. Sexually transmitted diseases can be treated with a single dose of 1g. The elderly can be administered as an adult. For children over 6 months (under 45 kg), the daily dose is 10 mg/kg, and the dosage and course of treatment are the same as adults. If taking azithromycin suspension, take 5ml (200 mg) for 3~7 years old (15~25 kg), take 7.5ml (300 mg) for 8~11 years old (26~35 kg), and take 10ml for 12~14 years old (36~45 kg).

Azithromycin side effects

1. Adverse reactions

  • Blood and lymphatic system abnormalities: Transient neutropenia is occasionally seen in clinical trials, but there is no data to show that it is related to azithromycin. Ear and labyrinth abnormalities: Some patients have experienced hearing loss after taking azithromycin, including hearing loss, tinnitus and/or deafness. According to investigations and studies, this phenomenon is related to patients' continuous high-dose use of this product. Through follow-up of these patients, it is found that most patients' hearing can be restored.
  • Gastrointestinal abnormalities: nausea, vomiting, diarrhea, loose stools, abdominal discomfort (pain or cramps), flatulence.
  • Abnormal hepatobiliary system: abnormal liver function.
  • Skin and subcutaneous soft tissue abnormalities: allergic reactions including skin rash and angioedema

After the listing, other adverse events reported during the use of this product include:

  • Infection and planting: candidiasis and vaginitis.
  • Blood and lymphatic system abnormalities: thrombocytopenia.
  • Immune system abnormalities: allergic reactions (rarely fatal).
  • Abnormal metabolism and nutrition: anorexia.
  • Mental disorders: aggressive reaction, nervousness, anxiety.
  • Nervous system abnormalities: dizziness, convulsions (similar to other macrolides), headache, increased activity, numbness, paresthesia, drowsiness, fainting. Rare reports of taste/olfaction and/or absence show. However, it is not clear whether it is related to medication.
  • Abnormal ears and labyrinth: dizziness.
  • Heart abnormalities: palpitations and arrhythmias including ventricular tachycardia (like other macrolides) have been reported; QT prolongation and torsade de pointes type ventricular tachycardia are rarely reported. However, it has not been confirmed that the above adverse events are related to azithromycin.
  • Vascular abnormalities: hypotension.
  • Gastrointestinal abnormalities: vomiting/diarrhea (rarely dehydrated), indigestion, constipation, pseudomembranous enteritis, pancreatitis, and tongue discoloration (rare).

2. Azithromycin contraindications

  • Like erythromycin and other macrolides, severe allergic reactions such as angioedema and allergies (rarely fatal) are rarely reported. Some reactions caused by azithromycin can recur and require a longer period of observation and treatment.
  • Since the liver is the main way to eliminate azithromycin, azithromycin should be used with caution in patients with obvious liver disease.
  • It has been reported that patients receiving ergot derivative treatment will develop ergot poisoning when taking certain macrolide antibiotics at the same time. Although there is no data showing that ergot interacts with azithromycin, ergot poisoning is theoretically possible, so azithromycin and ergot derivatives should not be administered simultaneously.
  • As with other antibiotic preparations, attention should be paid to the symptoms of double infection caused by non-susceptible bacteria including fungi.
  • Almost all antimicrobial applications have reports of Clostridium difficile-associated diarrhea (CDAD), including azithromycin, whose severity can range from mild diarrhea to fatal enteritis. Antimicrobial treatment can cause changes in the normal flora of the colon, leading to overgrowth of Clostridium difficile. Toxin A and Toxin B produced by Clostridium difficile are related to the pathogenesis of CDAD. The highly toxic Clostridium difficile leads to increased morbidity and mortality. These infections may not be effective in antibacterial treatment and may require colon resection. For all patients with diarrhea after using antibiotics, the possibility of CDAD must be considered. Since there have been reports of CDAD occurring more than 2 months after antimicrobial treatment, it is necessary to ask for a careful medical history.
  • In patients with severe renal insufficiency (glomerular filtration rate <10ml/min), the systemic exposure to azithromycin increased by 33%.
  • It has been reported that the application of other macrolide antibiotics can cause cardiac repolarization and prolongation of the QT interval, leading to the risk of arrhythmia and torsade de pointes ventricular tachycardia. When the risk of prolonged repolarization of the heart increases, azithromycin cannot be completely ruled out for similar effects.
  • There is no evidence that azithromycin has an effect on the patient’s ability to drive and operate machinery.

3. Azithromycin Interactions

This product has no interaction with theophylline, warfarin, carbamazepine, prednisone methyl, etc. Take this product 1h before or 2h after taking the antacid. Two hours before taking this product, a single dose of cimetidine does not affect the blood concentration of this product. Some macrolides can affect the metabolism of digoxin. Therefore, continuous application of this product may increase the blood concentration of digoxin, so attention should be paid.

This product should not be used in combination with ergot drugs, because it can cause ergot poisoning in patients; in addition, macrolides have been reported to increase digoxin (change the intestinal flora), cyclosporine and carmidazine (Inhibit metabolism) blood concentration, so when AM and these three drugs are taken at the same time, it may also increase the blood concentration of these drugs. The blood concentration of the latter should be monitored when these medicines are combined.

According to a domestic data, among the 19 patients with adverse reactions due to oral azithromycin, 3 increased the number of daily medications themselves, and 5 continued to take the medication for more than 5 days, resulting in increased adverse reactions due to irregular medication. The risk reaches more than 40%. In fact, as a long-acting drug, azithromycin only needs to be taken once a day.

Azithromycin is a new generation of macrolide antibiotics. Compared with erythromycin, it has stronger antibacterial activity, wider antibacterial spectrum and fewer adverse reactions. Another extremely important feature is that azithromycin has a typical post-antibiotic effect, which is related to its long blood half-life.

Relevant data show that after oral or intravenous infusion of azithromycin, its blood half-life can be as long as 35 to 48 hours, so azithromycin can still maintain the minimum effective inhibitory concentration within 72 hours after stopping the drug. This feature, on the one hand, makes it have a long-acting effect. It only needs to be taken once a day to achieve the same therapeutic effect as erythromycin taken multiple times a day.

On the other hand, it does not need to be administered continuously. When applying azithromycin to treat mycoplasma pneumonia and mycoplasma infectious diseases of the urogenital tract, sequential therapy is often adopted, that is, the drug is administered for 3 days and then stopped for 4 days, and the circle continues. In this way, taking the medicine once a day and taking the medicine for a short period of time can significantly increase the patient's compliance and significantly reduce the adverse reactions.

However, some patients have not yet realized this characteristic of azithromycin, or they are based on the habit of taking the drug 3 times a day, or they feel unsafe for taking the drug only once a day and "serving 3 and stopping 4", so they increase the number of medications at will, took azithromycin several times a day, or decide to continue medication by themselves. The results are not helpful to improve the condition, only to increase the adverse reactions.

Therefore, patients should strictly follow the doctor's advice, take azithromycin only once a day, and prevent multiple medications for a day and long-term medication.


Azithromycin has a good effect on many infections, but the side effects and drug resistance of Azithromycin are evident. We must strictly follow the doctor's instructions to control the azithromycin dosage.


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