What Is a Z-Pak and What Is It Used For?

Azithromycin is a commonly prescribed antibiotic. It's also called Zithromax, Azithro, Z-pak, or Zmax. It is used for a variety of infections caused by bacteria. It is however frequently overprescribed.

The drug is usually given as a pill orally, but it can be given Intravenously. It is usually given once a day, sometimes twice a day. When given as a Z-Pak, it is a pre-packaged 5-day course. However, azithromycin is not always given as 5-day courses.

Your healthcare provider will explain the dosing you need.

What is it used for?

Azithromycin is an antibiotic approved by the US FDA (Food and Drug Administration) for treating certain infections:

  • Bacterial respiratory infections, including pneumonia and acute sinus and ear infections.
  • Pelvic inflammatory disease.
  • Genital ulcer disease.
  • Infections of the urethra, cervix, and skin.

This means the drug is often used as a treatment for pneumonia, as it covers both common bacterial causes of pneumonia (like Strep pneumoniae) and atypical causes (like legionella, Chlamydia pneumoniae, and mycoplasma). Likewise, it is also used for exacerbations of COPD, ear infections, tonsillitis, sinusitis, when caused by bacteria.

Azithromycin is an important drug for some STDs. It is the first line treatment for chlamydia, an STD (sexually transmitted disease) tied to infertility. It is part of the first line for gonorrhea, another STD, as well as chancroid (Haemophilus ducreyi).

It is also used for pelvic inflammatory disease (PID).

It can also be used for some skin infections.

In addition, the antibiotic is used for other indications, other than the standard FDA-approved uses. It can be given as part of the treatment for Helicobacter pylori (H pylori, a bacteria that can lead to stomach ulcers).

Additionally, it is used for the treatment of some bacterial diarrhea infections, like Traveler's Diarrhea.

It is often over-prescribed.

Antibiotics only work against infections caused by a bacteria. Using antibiotics for non-bacterial infections does not help fight the infection. Such use can put the patient at risk for side-effects and for drug-resistance.

Many sinus, ear, and throat infections are not caused by bacteria, but are rather due to viruses. Doctors may prescribe antibiotics just in case, but the infection would have gone away without the antibiotics. The viral infection will go away because our immune systems will have fought off the virus. When the infection clears, some will think the antibiotic helped them - but it didn't play a role. Taking the antibiotic in this case just leads to the side effects of the antibiotics.

Antibiotic misuse also leads to the development of drug resistance. We are full of bacteria - in our guts and our skin. These are not just bugs that bother us; many play important roles.

By washing away our normal bacteria, we can select out for resistant strains, allow ourselves to be colonized with resistant strains, or create a situation where drug resistance strains develop. It's important to only use antibiotics when they are needed. Resistant bacteria are harder to treat; future infections that are actually caused by bacteria might not be easily treated.

We can find ourselves newly carrying resistant bacteria when we take antibiotics, even if the infection was bacterial, but it might have gone away on its own, like with Traveler's Diarrhea. Some travel with azithromycin or another antibiotic (like ciprofloxacin) just in case they develop Traveler's Diarrhea. The traveler then has to choose whether to use the antibiotic if a bit of diarrhea starts up. It was found that those who took the antibiotics, which might not have been necessary, as diarrhea often passes, were more likely to come home with antibiotic resistant bacteria in their stools. It's important to talk to a healthcare provider to know when to take antibiotics like azithromycin for Traveler's Diarrhea.

With increased use of azithromycin - and other related antibiotics - we may be risking developing resistance throughout our communities. There is now azithromycin-resistant Shigella, a bacteria that causes diarrhea, which has been tied to travel and to men who have sex with men. (However, some of the strains of resistant Shigella are resistant to ciprofloxacin, and azithromycin remains the choice for treating). There is also now gonorrhea which has reduced susceptibility to azithromycin and bacteria causing pneumonia (Strep pneumomycoplasma, and pertussis) that are resistant. (In fact, resistance is highly prevalent in mycoplasma in Asia, has traveled to Europe, and now some resistance was seen in the US). It's possible the frequent use of this antibiotic and related antibiotics has led to this resistance in communities.

How often is it prescribed in the US?

In the US, per the New York Times (and similarly by the FDA), there are 55.3 million prescriptions each year. Sales are reported $464.4 million annually in the US and $1.8 billion globally. Patients know to ask for it by name. All of the antibiotics in the fluoroquinolone class of drugs - another common type of antibiotic which fights many of the same bacteria - account for 33.5 million prescriptions (with ciprofloxacin accounting for about 40%, 13.8 million in 2004)

Don't some people take it daily?

Azithromycin is also given to prevent infections in certain people who are very vulnerable. Some take azithromycin daily for prophylaxis. These uses are off-label from the FDA indications. Those who are HIV positive may be given azithromycin weekly to avoid the development of a particular type of infection (mycobacterial infection, such as Mycobacterium avium complex (MAC) disease) and can also prevent syphilis. It is also used in the treatment of Toxoplasma gondii (Toxoplasmosis encephalitis), MAC, campylobacteriosis and shigellosis, Bartonella, and syphilis.

The drug may also be used as prophylaxis for those who are allergic to penicillin and need prophylaxis to avoid endocarditis (infection of the heart valve).

Azithromycin is also being investigated to prevent malaria.

What other antibiotics are similar?

It is a macrolide antibiotic. This class includes Clarithromycin and Erythromycin, which normally would not be given at the same time as Azithromycin - as this would be redundant.

Azithro is in a different class than many other antibiotics. It's important that we do not lose this class to drug resistance. This is especially important because - as part of a different class of antibiotics - azithromycin can be effective against bacteria resistant to many other antibiotics.

Among other uses, azithromycin is important for STDs as well as atypical pneumonias and for treating those who are penicillin-allergic and for self-treatment of traveler's diarrhea.

What are the side effects?

Azithromycin can cause stomach upset, vomiting, diarrhea.

There are more dangerous side effects that should prompt seeing a medical professional. In rare cases, it can cause liver problems, which can be serious. It also can rarely cause hearing loss or ringing in the ears (tinnitus). It can rarely cause headaches or changes in taste or smell. Rash can also occur.

Some develop Clostridium Difficile. This happens when an antibiotic, like azithromycin, flushes out the microflora - bacteria - in the intestines that make up part of our microbiome. This can be a serious disease.

In very rare cases, Azithromycin can lead to sudden death. This can be related to changes in the inherent electrical activity of the heart (QTc interval which is prolonged in some individuals at baseline). It can cause abnormal beating of the heart - which can be deadly - especially in those who already have an abnormality (which they may not know about). The study which showed this found an increase in cardiovascular deaths (and from any cause) in those treated with 5 days of azithromycin compared to those treated with amoxicillin, ciprofloxacin, or no drug. 

Use of the antibiotic can also be associated with developing drug resistance. Those who take it for Traveler's Diarrhea may flush out the bacteria in their intestines leading them to be repopulated with antibiotic resistant bacteria in their stools. This means future infections may be harder to treat.

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