Zithromax, sometimes called Z-Pak, is a popular form of the antibiotic azithromycin.
Azithromycin is the most commonly prescribed antibiotic in the United States.
It is a macrolide antibiotic that treats some bacterial infections by stopping the growth of the bacteria.
This process of stalling bacteria growth is why Z-Pak is called “bacteriostatic”—instead of killing bacteria outright, it stops them from growing and multiplying.
The body’s natural defenses can then remove what’s left of the bacteria. Azithromycin has no use in treating viral infections, including COVID-19, common colds, viral bronchitis, or most sinus infections.
If you’re wondering what a Z-Pak (or Z-Pack) is, how to use this medication, or whether it’s effective, this guide will help.
In this article, I’ll discuss the Z-Pak’s uses, doseage, and effectiveness, as well as risks and side effects.
I’ll talk about when not to take a Z-Pak, and some alternatives to Zithromax.
I’ll finish by outlining when you should see a doctor about your symptoms.
Azithromycin (Zithromax or Z-Pak) can be used to treat some bacterial infections of the skin, respiratory, and genitourinary system.
Here are some infections for which your doctor may prescribe a Z-Pak.
Strep throat, or streptococcal pharyngitis, is a bacterial infection of the throat.
It typically manifests as a sore throat, pain with swallowing, as well as a fever or a rash.
Penicillin antibiotics are the preferred treatment for strep throat, but some patients are allergic to these antibiotics. In these cases, your doctor may prescribe Zithromax instead.
Research has shown that Z-Paks treat strep throat just as well as penicillin for those with a penicillin allergy. Azithromycin does not work for viral throat infections.
Z-Pak is also effective for treating some types of community-acquired pneumonia, an acute respiratory infection contracted outside of the hospital.
Studies show that for patients treated with azithromycin, hospital stays were shorter despite a shorter course of antiobiotics.
Your provider may also choose to treat pneumonia with a combination of Z-Pak and another antibiotic for a stronger effect, as azithromycin does not treat all types of pneumonia well.
Azithromycin does not work for COVID-19 pneumonia or other viral pneumonias.
Bronchitis is an infection of the main chest airways called bronchi.
While most bronchitis is caused by viruses, the infection is sometimes caused by bacteria. In these bacterial cases, Z-Pak may be useful for treatment.
Most of the time, though, your doctor will probably not prescribe an antibiotic for bronchitis: A study in American Family Physician showed that antibiotics provide very little benefit in most cases of acute bronchitis.
However, when the bronchitis is caused by whooping cough or other specific bacteria, macrolides like Z-Pak are efficient for reducing the spread.
Other bacterial infections that can be managed with azithromycin are:
- Bacterial sinusitis: According to a study comparing the impact of amoxicillin-clavulanate and azithromycin, Z-Packs can treat sinus infections caused by bacteria. However, most sinus infections are caused by viruses, and do not need antibiotics at all. And when sinusitis is caused by bacteria, other antibiotics are generally preferred and more effective.
- Tonsillitis: Z-Pak works for treating tonsillitis in adults and children who cannot take penicillin-based antibiotics, though it may have more side effects.
- Ear infections (otitis media): Azithromycin is also effective for treating infections of the middle ear that are caused by bacteria in those who cannot take other preferred antibiotics.
- Mycobacterium Avium Complex (MAC) Lung Disease: Z-Pak is used to manage MAC lung disease, often seen in patients with HIV.
- Non-gonococcal urethritis: This inflammation of the male urethra, caused by the sexually-transmitted disease chlamydia, can be treated with azithromycin, though doxycycline is often the preferred antibiotic.
- Pelvic Inflammatory Disease (PID): PID should be treated with the antibiotic doxycycline, but in those who cannot take doxycycline, azithromycin may be used in combination with another antibiotic.
- Cervicitis: Experts recommend either doxycycline or azithromycin for the treatment of chlamydial cervicitis, though doxycycline is the recommended treatment. When cervicitis is caused by gonorrhea, a different antibiotic is required.
- Lyme disease: The CDC recommends that people with early Lyme disease who cannot tolerate doxycycline, cefuroxime, or amoxicillin be treated with azithromycin—although it is less effective than the other three in this case.
Dosage of Zithromax
Azithromycin comes in various dosages, but a Z-Pak is a specific, five-day course of azithromycin.
The Z-Pak contains six tablets, each containing 250 mg of azithromycin.
Two tables are taken on the first day (for a 500 mg dose), followed by one 250 mg tablet taken each of the next four days.
This is a common dose for many types of infections.
Azithromycin is available as oral tablets, oral suspension (liquid), and injections or intravenous (IV) medication.
Each of the available forms come in several strengths.
- Oral tablets: Available as 250 mg and 500 mg tablets.
- Oral suspension: Available as 100 mg/5 mL and 200 mg/5 mL suspensions.
- Injection and IV: Available as 10 mL vial of 500 mg.
Your doctor will decide what dosage is appropriate for you depending on your age and the infection.
The prescribed strength and form may also vary over the course of your treatment.
For example, the recommended dose for strep throat is 500 mg oral tablets once on the first day, followed by 250 mg oral tablets for the next four days. But for non-gonococcal urethritis, it’s a one-time, 1000 mg dose.
How Long to Take It
Take your azithromycin for the duration prescribed by your provider.
Usually, this is between 3-10 days. Make sure to take the medication on time and complete the full treatment course before discontinuing the drug—even if you’ve begun to feel better.
Starting and quitting the drug before the specified day can cause bacteria to become resistant to antibiotics.
Effectiveness of Azithromycin
Azithromycin is a versatile and highly effective antibiotic when used appropriately.
It works well in treating a wide range of bacterial infections both in children and adults.
Azithromycin is especially effective in treating some sexually transmitted infections, like chlamydia and chlamydia-related infections.
One clinical showed that azithromycin showed a 98% eradication for chlamydia and other bacteria.
Possible Risks and Side Effects of Azithromycin
The most common side effects of azithromycin are not life-threatening for most people.
Still, it’s worth knowing what they are so you don’t panic, and can get help from your doctor if needed.
Side effects you may experience with azithromycin are:
- Upset stomach
- Loose stools or diarrhea
- Dizziness or fainting
- Skin rash
- Abdominal pain
- Vaginal itchiness from yeast overgrowth
- Ringing ears
- Blurred vision
- Liver problems
Azithromycin may interact with several other medications, causing them to be ineffective, or potentially causing serious side effects.
Be sure to mention all your current medications to your prescriber before receiving a prescription for azithromycin.
A few drugs that interact with azithromycin are:
- Antipsychotic medications
- Anti-malarial medications
- Heart rhythm medications
- Cholesterol-reducing medication
- Blood pressure medication
- Anti-diarrheal medications
- HIV medicines
If you take any of these medications, your provider may need to prescribe alternative medication or recommend pausing them for the duration of your antibiotic treatment.
When to Not Take Azithromycin
In some cases, azithromycin is not the right choice.
Here are some situations in which you should avoid azithromycin.
While azithromycin works for treating some sexually transmitted infections, specifically those caused by chlamydia, it should not be used to treat gonorrhea and syphilis, or trichomonas.
The CDC also now recommends doxycycline as the first-line treatment for chlamydia, not azithromycin.
If you have an allergy or other inability to take doxycycline, then azithromycin may be used.
Children under six months of age should not be treated with azithromycin.
Recent studies show that azithromycin is safe for use in the elderly.
While azithromycin does not cause fetal malformations in the uterus, it has been associated with an increased risk of miscarriage.
If you have heart problems—especially irregular heartbeats like QT prolongation—it would also be best to avoid using azithromycin.
A study in the New England Journal of Medicine showed that use of the antibiotic increased the risk of sudden death linked to heart arrhythmias.
Many common infections, including colds, sinus infections, bronchitis, and some ear and throat infections, are caused by viruses.
Unfortunately, when your illness is caused by a virus, an antibiotic will not help at all, and can cause uncomfortable or serious side effects.
Alternatives to Azithromycin
For those unable to use azithromycin or other macrolides such as erythromycin and clarithromycin, there are other antibiotics you can be prescribed instead.
Amoxicillin is a penicillin-like antibiotic that treats many of the same bacterial infections azithromycin does.
Because of antibiotic resistance, it is sometimes used with clavulanate as amoxicillin-clavulanate (Augmentin).
This broad-spectrum antibiotic treats everything from respiratory tract infections to gastrointestinal infections. And it is safe for most people, including those who are pregnant.
Doxycycline (Monodox) is especially useful for urogenital infections such as chlamydia.
Some studies have shown it to be more effective than azithromycin, and the CDC now recommends doxycycline as the first-line treatment for sexually transmitted infections caused by chlamydia.
Ceftriaxone (Rocephin) treats bacterial pneumonias, ear infections, and throat infections, and may be used instead of, or in addition to, azithromycin for some types of infections.
Your doctor or healthcare provider will make the best choice for you when they know which medications you’re on and which other medical conditions you have.
When to See a Doctor
If you have worrying signs of an infection, it’s best to see your primary care physician before beginning antibiotic treatment using azithromycin.
Many common infections are actually viral, and will resolve on their own without antibiotics.
Azithromycin is not the right treatment for all types of bacterial infections.
Your provider can determine if antibiotics are needed at all, which antibiotics are safe and effective for your infection, and what dosage will work best.
If you have already begun using azithromycin and are not seeing improvement in your symptoms or are getting worse, speak to your healthcare provider.
How K Health Can Help
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Frequently Asked Questions
K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.
K Health has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations. We avoid using tertiary references.
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Doxycycline as an Alternative to Azithromycin in Elderly Patients. (2021).
Use of antibiotics during pregnancy and risk of spontaneous abortion. (2017).
Management of non-gonococcal urethritis. (2015).
Effectiveness of azithromycin in aspiration pneumonia: a prospective observational study. (2014).
Azithromycin for Elderly Patients With Pneumonia. (2014).
Azithromycin and the Risk of Cardiovascular Death. (2012).
Diagnosis and Treatment of Acute Bronchitis. (2010).
Newest Approaches to Treatment of Pelvic Inflammatory Disease: A Review of Recent Randomized Clinical Trials. (2007).
Single dose azithromycin for the treatment of uncomplicated otitis media. (2004).
Is azithromycin the first-choice macrolide for treatment of community-acquired pneumonia? (2003).
Randomized Double-Blind Study Comparing 3- and 6-Day Regimens of Azithromycin with a 10-Day Amoxicillin-Clavulanate Regimen for Treatment of Acute Bacterial Sinusitis. (2003).
Chlamydial Infection Among Adolescents and Adults. (2021).
Azithromycin versus penicillin V for treatment of acute group A streptococcal pharyngitis. (2002).
Azithromycin-Containing Regimens for Treatment of Mycobacterium avium Complex Lung Disease. (2001).
Azithromycin vs cefuroxime plus erythromycin for empirical treatment of community-acquired pneumonia in hospitalized patients: a prospective, randomized, multicenter trial. (2000).