Why do we need to use azithromycin for 3 days and stop for 4 days? Will it weaken the efficacy of the drug?

A friend consulted Huazi. When he was taking azithromycin, the doctor told him to stop taking it for 4 days after taking it for 3 days, and then see the test results to decide whether to take a second course of treatment. He didn't understand. Doesn't the drug need to be taken all the time for the effect to be good? Wouldn't stopping the drug for such a long time weaken the efficacy of the drug?

Huazi said, "Use 3 days and stop 4 days" is a classic method of using azithromycin. Because azithromycin is metabolized relatively slowly, after 3 days of medication, the blood concentration is already relatively high, and even if the medication is stopped, it will not affect the efficacy.

1. Azithromycin has a long half-life. After the drug is absorbed by the human body, the blood concentration reaches its peak and then gradually decreases. The time it takes for the blood concentration to drop by half is called the half-life of the drug. The longer the half-life, the longer the duration of the drug effect. The half-life of azithromycin is 1.5 to 2 days. After stopping the drug for 4 days, there will still be about 12.5% ​​to 25% of azithromycin in the human body.

Moreover, azithromycin has a post-antibiotic effect, which means that after the antibiotic comes into contact with the pathogen, even if the drug concentration drops below the minimum inhibitory concentration or even after being metabolized and eliminated, the pathogen will still be continuously inhibited. Azithromycin has a long half-life and a post-antibiotic effect. These two characteristics are the theoretical basis for the "use 3, stop 4" policy of azithromycin.

2. Azithromycin and macrophages work together. Another characteristic of azithromycin is that it can be phagocytosed by macrophages. Macrophages will migrate in the interstitial space and gather at the site of infection, carrying azithromycin to the site of infection, thus forming a higher drug concentration at the site of infection and improving the antibacterial effect of azithromycin.

This effect is also known as the "Trojan Horse phenomenon", which means hiding azithromycin in the "Trojan horse" of macrophages to attack the "Trojan" castle of pathogens.

Therefore, because azithromycin has a long half-life, post-antibiotic effect, and Trojan horse phenomenon, it can be used in the “use 3, stop 4” strategy to treat sensitive bacteria.

3. Different ways to use azithromycin In actual application, when azithromycin is used for mild and moderate infections caused by sensitive bacteria, the method of "use 3, stop 4" can be adopted, and its efficacy is equivalent to that of cephalosporins used continuously for 7 days. In addition, due to the short medication time, only one dose is needed per day, and the medication compliance is higher than that of cephalosporins.

The specific usage of "use 3, stop 4" means taking 0.5g of azithromycin once a day for 3 consecutive days and then stop for 4 days, a total of 7 days as a course of treatment. After that, depending on the changes in the condition, consider whether to carry out a second course of treatment.

Another method is "use 5 and stop 3", which means taking 0.5g of azithromycin on the first day, and then taking it for 4 consecutive days, 0.25g of azithromycin per day, for a total of 5 days, and then stop taking it for 3 days. A course of treatment is 8 days.

However, the resistance rate of azithromycin is relatively high now, with the resistance rate of Streptococcus pneumoniae to azithromycin being around 90% and that of Mycoplasma pneumoniae being around 60%. Therefore, for community-acquired pneumonia and those with severe infection, intravenous or oral administration is required for 5 to 7 days, and a second course of treatment is carried out after an interval of 2 to 3 days.

If the pathogen has a high resistance rate to azithromycin, consider using tetracyclines and quinolones for treatment.

To summarize, azithromycin has a long half-life, has antibiotic effects and Trojan horse phenomena, so for mild and moderate infections with sensitive pathogens, azithromycin can be administered using the "use 3, stop 4" method to improve medication compliance and reduce adverse reactions caused by drug accumulation. Azithromycin is a prescription drug and can only be used safely under the guidance of a doctor. If you have any questions about medication, please consult a doctor or pharmacist in time. I am pharmacist Huazi, welcome to follow me and share more health knowledge.