Is Azithromycin Still Working After The Last Dose?
In our latest question and answer, the pharmacist discusses how long azithromycin lasts after your last dose.
Is azithromycin still effectively killing bacteria after the last dose, or 'half-life' period? Thank you!
Apr 27, 2022- Azithromycin continues to work for about 5 days after your last dose because of its long half-life, which means the medication stays in your system for an extended period. If your infection hasn't improved by day 5 of treatment, the medication is likely still working and you should see improvement soon after. If you notice no improvement a few days after finishing the medication, contact your doctor.
Hi Chico and thanks for reaching out to us.
Azithromycin is a very commonly used antibiotic to treat a variety of infections such as sinus infections, ear infections, upper respiratory infections, and several other common bacterial infections.
One of the big advantages of using azithromycin is the ease of dosing. Many antibiotics are dosed three or four times daily. Azithromycin is always just once a day. This is due to its long half-life. The 'half-life', in this sense, is the amount of time that it takes for your body to metabolize half of the medication and remove it from your body. The half-life for adults is variable, but it averages 68 hours for azithromycin.
What this means is that if you were to take a single dose of azithromycin, after 68 hours half of the initial dose would still be in your system.
The most common form of azithromycin is the 5-day Z-Pack. You take 2 tablets on day 1, 1 tablet on days 2-5, and then stop. Due to the long half-life of azithromycin, it keeps working to treat bacterial infections for another 5 days or so after your last dose, simply due to the fact that you’ve been taking it regularly for the last 5 days.
So, if it doesn't seem like your infection is getting better after 5 days of being on azithromycin, that's generally okay...it is still working, and you should see an improvement soon. If you still see no improvement a few days after your last dose, be sure to reach out to your doctor.
I hope this helps! Feel free to write us again in the future.
Glossary — Terms in This Answer
- Antibiotic
- A medication that kills bacteria or stops them from growing to treat infections.
- Sinus infections
- An infection in the air-filled cavities in the bones around your nose and eyes.
- Upper respiratory infections
- An infection affecting the nose, throat, and upper airways.
- Bacterial infections
- Infections caused by harmful bacteria that invade and multiply in the body.
- Half-life
- The amount of time it takes for your body to break down and remove half of a medication.
- Metabolize
- The process by which your body breaks down a substance into forms it can use or eliminate.
- Z-Pack
- A common 5-day package of azithromycin tablets with a specific dosing schedule.
Dr. Brian Staiger, PharmD
Doctor of Pharmacy, board certified clinical pharmacist (BCPS), American Herbalist Guild, Medication Therapy Management certified
Brian Staiger, PharmD, BCPS, is a licensed pharmacist with more than 13 years of experience across retail pharmacy, clinical pharmacy, medication safety, pharmacy program development, and healthcare administration. He is the founder of HelloPharmacist.com, where he helps patients...
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