Azithromycin is an antibiotic drug. In the U.S., its brand name is Zithromax. It is sold under many other brand names, including Ultreon, in other countries. Antibiotics fight infections caused by bacteria. Azithromycin is used to fight opportunistic infections (OIs) in people with HIV.


Azithromycin is used for mild or moderate bacterial infections. It works against several different bacteria, especially chlamydia, hemophilus, and streptococcus. These bacteria can infect the skin, nose, throat, and lungs. They can also be transmitted through sexual activity and cause infections in the genital area.

Many germs live in our bodies or are common in our surroundings. A healthy immune system can fight them off or keep them under control. However, HIV infection can weaken the immune system. Infections that take advantage of weakened immune defenses are called opportunistic infections (OIs). People with advanced HIV disease can get OIs.

One OI in people with HIV is mycobacterium avium complex (MAC). People who have a CD4 cell count of less than 50 cells/mm3 may develop MAC.

Azithromycin is often used with another antibiotic to treat MAC. It can also be used to prevent MAC infection. If your CD4 cell count is below 50 cells/mm3, talk to your healthcare provider about using azithromycin.

Azithromycin is also used to treat other OIs such as toxoplasmosis (toxo) and cryptosporidiosis.

Some people are allergic to azithromycin and similar antibiotics. Be sure to tell your healthcare provider if you are allergic to azithromycin or other antibiotics.


Whenever you take medication, be sure to take all of the prescribed doses. Many people stop if they feel better, but this is not a good idea. If the drug doesn’t kill all of the germs, they might change (mutate) so that they can survive even when you are taking medications. When this happens, the drug will stop working. This is called developing resistance to the drug.

For example, if you are taking azithromycin to treat MAC and you miss too many doses, the MAC in your body could develop resistance to azithromycin. Then you would have to take a different drug or combination of drugs to treat MAC.


Azithromycin is available in capsules or tablets of 250 or 600 milligrams (mg). It is also available in powder and liquid forms. To treat most infections, the dose for adults is 500 mg on the first day then 250 mg each day for 4 more days.

The dose used to prevent MAC infection is 1200 mg or 1250 mg once a week.

Azithromycin tablets can be taken with or without food, but should be taken with plenty of water. The capsules or liquid should be taken on an empty stomach, either 1 hour before eating or 2 hours after eating. Be sure to check the instructions carefully.

Do not take azithromycin at the same time as antacids that contain aluminum or magnesium. They will reduce the amount of azithromycin in your blood.


The side effects of azithromycin mostly affect the digestive system. They include diarrhea, nausea, and pain in the abdomen. Some people get very sensitive to sunlight. Others may get headaches, dizziness, fatigue, or have problems hearing. Very few people who take azithromycin get these side effects. However, most antiretroviral medications (ARVs) also cause problems in the digestive system. Azithromycin could make those problems worse.

Some people get a severe allergic reaction to azithromycin. Let your healthcare provider know immediately if you get severe diarrhea, fever, joint pain, serious stomach cramps or pain, swelling in your neck, mouth, hands, or feet, or trouble breathing.

Antibiotics kill some helpful bacteria that normally live in the digestive system. You can eat yogurt or take supplements of acidophilus to replace them.


Azithromycin is broken down by the liver. It can interact with other drugs that also use the liver. Scientists have not yet studied all the possible interactions. Azithromycin probably interacts with some blood thinners, heart medications, seizure medications, and other antibiotics. Be sure your healthcare provider knows about all the medications and supplements you are taking.

Your healthcare provider may need to monitor you carefully if you are taking azithromycin and the protease inhibitor (PI) ritonavir (Norvir).

Antacids with aluminum or magnesium can lower blood levels of azithromycin. Do not take antacids at the same time as azithromycin.


Azithromycin is used to treat MAC, toxoplasmosis, and cryptosporidiosis. It can prevent new infections or treat active infections. If your CD4 cell count is below 300 cells/mm3, talk to your healthcare provider about taking drugs to prevent these infections.


MedlinePlus: Azithromycin

Drugs.com: Azithromycin

Reviewed March 2021

Print PDF