Cayston (Aztreonam) - Inhalation

What Is Cayston?

Cayston (aztreonam) is a prescription antibiotic available for people ages 7 and older with cystic fibrosis (CF) who experience lung infections due to certain bacteria called Pseudomonas aeruginos.

Its primary ingredient, aztreonam, is in a drug class called monobactam antibiotics.

Monobactam antibiotics work to treat infections of the urinary tract or lower respiratory tract, gynecologic infections, septicemia (problems that arise from the toxins released by the bacteria into your bloodstream), and cutaneous (skin) infections.

This medication works by binding to bacteria and preventing them from growing and spreading, causing cell death.

Cayston is available in the form of a solution that is inhaled through a nebulizer (a device that changes a drug from a liquid to a mist) called the Altera nebulizer in brand form only.

Drug Facts

Generic Name: Aztreonam

Brand Name(s): Cayston

Drug Availability: Prescription

Therapeutic Classification: Monobactam antibiotic

Available Generically: No

Controlled Substance: No

Administration Route: Inhalation

Active Ingredient: Aztreonam

Dosage Form(s): Solution for nebulizer

What Is Cayston Used For?

The Food and Drug Administration (FDA) approved Cayston to improve breathing symptoms in people with CF who have been infected with the Pseudomonas aeruginosa bacteria.

CF is a genetic disorder that causes severe damage to the lungs, digestive system, and other organs in the body. In people with CF, mutations in the CF transmembrane conductance regulator (CFTR) gene cause the CFTR protein (a mechanism of the body that helps to maintain the balance of salt and water on many surfaces in the body) to become dysfunctional.

The Pseudomonas aeruginosa (a major cause of lung infections in people with CF) bacteria is found commonly in the environment, specifically in mounds of soil and bodies of water. While there are many types of Pseudomonas, the one that most often causes infections in humans is Pseudomonas aeruginosa, which can cause infections in the blood, lungs (pneumonia), or other parts of the body following surgery.

To fight this, Cayston can be used with a one-second forced expiratory volume (FEV1; a measure of how much air a person can exhale) between 25% and 75% via the Altera nebulizer. Cayston does not treat viral infections such as the flu, common cold, or COVID-19.

How to Take Cayston

If you are prescribed Cayston, read the label, information leaflet, and medication guide that comes with your prescription. Consult your healthcare provider if you have any questions. Use Cayston exactly as directed by your healthcare provider.

Refer to the label for use directions on preparing and using Cayston. Cayston is usually used three times a day (at least four hours apart) for courses of 28 days on and then 28 days off.

Use Cayston only with the Altera nebulizer. Do not mix other medications with Cayston in the nebulizer. Make sure you understand how to mix Cayston with saline before pouring it into the nebulizer. Prepare the dose when you are ready to use the nebulizer. Notify your pharmacist if the solution looks cloudy or has particles in it.

Discard the bottle after one use, even if it looks like there is medicine left in the bottle. Also, discard the saline ampule and stopper. Your healthcare provider may instruct you to use a bronchodilator medication to help open the lungs before each dose of Cayston.

If you use a short-acting bronchodilator like albuterol (brand names: ProAir HFA, Proventil, and Ventolin), use it between 15 minutes and four hours before using Cayston. If you use a long-acting bronchodilator such as Dulera or Symbicort (budesonide and formoterol), use it between 30 minutes and 12 hours before using Cayston.

If you also use medication to clear mucus from the lungs, use it after the bronchodilator, but before Cayston. Finish the full course (28 days) of antibiotics, even if you feel better. Skipping doses can cause antibiotic resistance, and the antibiotic may not work as well the next time you need it.

Your healthcare provider will tell you exactly how long you need to take it and if you need to take several courses of treatment.

Talk to your healthcare provider if you have any questions or concerns about Cayston.


Store Cayston and the saline ampules in the refrigerator, away from direct light. Once you take Cayston out of the refrigerator, you can store both Cayston and the saline at room temperature for up to 28 days. Do not separate the vials of Cayston from the vials of saline.

Do not use Cayston if it has been stored at room temperature for over 28 days. Do not use Cayston or the saline after the expiration date. Only mix one dose at a time. Once Cayston is mixed with saline, use the medicine in the Altera nebulizer right away. Do not use the medicine if it is cloudy or contains particles.

Off-Label Uses

Off-label prescribing is when a drug is prescribed for a purpose that is not FDA-approved.

Although Cayston is only FDA approved for people with CF, one clinical trial studied inhaled Cayston in people who did not have CF but who had other lung conditions, such as bronchiectasis (damaged lung airways which make it difficult to clear mucus), people who have had a lung transplant, and people who have had frequent infections.

How Long Does Cayston Take to Work?

You may start to feel better quickly, but it is important to finish the entire 28-day course of antibiotics. Your healthcare provider will tell you how to take Cayston, usually for 28 days on and then 28 days off. Follow the directions exactly so that Cayston works properly to eliminate bacteria.

What Are the Side Effects of Cayston?

This is not a complete list of side effects, and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your pharmacist or a healthcare provider. You may report side effects to the FDA at or 1-800-FDA-1088.

Like other medications, Cayston can cause side effects. Tell your healthcare provider about any side effects you experience while taking this medication.

Common Side Effects

Common side effects of Cayston include:

  • Cough
  • Stuffy nose
  • Wheezing (a high-pitched whistling sound made while breathing, usually while having difficulty breathing)
  • Sore throat
  • Fever
  • Chest discomfort
  • Stomach pain
  • Vomiting
  • Bronchospasm (wheezing and coughing due to tightening of the airways)
  • Rash

Severe Side Effects

Call your healthcare provider right away if you have serious side effects. Call 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency.

Serious side effects and their symptoms can include the following:

  • Hypersensitivity reaction or anaphylaxis: Symptoms can include rash, hives, swelling around the lips, tongue, and face, difficulty breathing, and require emergency medical attention. 
  • Bronchospasm: Be alert to wheezing, cough, chest tightness, trouble breathing

Long-Term Side Effects

A study was done that looked at long-term treatment with Cayston, for 18 months (nine courses of treatment of 28 days on and then 28 days off):

The study did not find any new safety concerns. The study found that using Cayston three times a day improved lung function over the 18-month period. Weight gain occurred with long-term use, which is beneficial to people with CF who often have poor weight gain.

With long-term antibiotic treatment, antibiotic resistance is always a concern. Antibiotic resistance is when bacteria change and develop the ability to stay alive despite antibiotic medication. In this study, antibiotic resistance was not a problem with Cayston.

People should discuss long-term side effects with their healthcare providers.

Report Side Effects

Cayston may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication. If you experience a serious side effect, you or your healthcare provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

Dosage: How Much Cayston Should I Take?

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The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For inhalation dosage form (solution in a nebulizer):
    • For lung infections:
      • Adults, teenagers, and children 7 years of age and older—One vial or container with 75 milligrams (mg) three times per day for 28 days in the nebulizer. You should space the doses at least 4 hours apart.
      • Children younger than 7 years of age—Use and dose must be determined by your doctor.


Users should be aware of the following before beginning Cayston:

Children: Cayston is approved for use in adults and children 7 years and older. It is not approved for children younger than 7 years old.

People with kidney problems: People with mild, moderate, or severe kidney problems can use Cayston and will not require a dosage adjustment.

Pregnant people: Although there is little data, Cayston can be used in pregnancy or nursing as long as the healthcare provider determines it is safe.

Nursing people: There are no data on the effects of aztreonam on the breastfed infant or the effects on milk production.

However, the developmental and health benefits of breastfeeding should be considered along with the person's clinical need for Cayston and any potential negative effects on the breastfed infant from Cayston or the underlying condition.

Missed Dose

If you miss a dose of Cayston, take it as soon as you can. Then, wait four hours before the next dose. Do not use two doses at once. Even if a dose is missed, try to use all three doses for the day, as long as you can space them at least four hours apart.

Overdose: What Happens If I Take Too Much Cayston?

Clinical trials have not returned any evidence of Cayston-related overdoses. However, studies showed that 225-milligram doses of Cayston taken via inhalation correlated with higher rates of drug-related respiratory adverse issues, particularly cough.

Still, if you think you took too much Cayston, follow the directions below.

What Happens If I Overdose on Cayston?

If you think you or someone else may have overdosed on Cayston, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn't breathing after taking Cayston, call 911 immediately.


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It is very important that your doctor check the progress of you or your child at regular visits. This will allow your doctor to make sure this medicine is working properly and to check for unwanted effects.

This medicine may cause bronchospasm, which may be life-threatening. Check with your doctor right away if you or your child are having a cough, difficulty with breathing, shortness of breath, or wheezing after using the medicine.

Stop using this medicine and check with your doctor right away if you or your child develop a skin rash, hives, swelling of the face, tightness in the throat, or any allergic reaction to aztreonam.

If your or your child's symptoms do not improve or if they get worse, call your doctor.

What Are Reasons I Shouldn't Take Cayston?

Cayston is not appropriate for everyone. Before taking Cayston, tell your healthcare provider about your medical conditions, medical history, and family history.

You should not take this medication if you are allergic to aztreonam or any of the inactive ingredients in Cayston.

Cayston may be prescribed with caution in some people, only if the healthcare provider determines it is safe. This includes people who are allergic to beta-lactam antibiotics, such as penicillin, Moxatag (amoxicillin), or Augmentin (amoxicillin and clavulanate).

What Other Medications May Interact With Cayston?

There are no known drug interactions with Cayston.

Still, it is important to tell your healthcare provider about all your medicines, including prescription and over-the-counter (OTC) medicines, and vitamins or supplements, while taking Cayston.

What Medications Are Similar?

Cayston contains aztreonam in an inhaled solution, that is used in the Altera nebulizer, for people with CF who have lung infections caused by the bacteria Pseudomonas aeruginosa.

Some alternatives to Cayston include:

CF treatment usually requires various medications.

For example, people with CF may also need digestive enzymes to help their body absorb nutrients and inhaled bronchodilator medications to help open up the lungs. There are also medications that target genes for people with certain gene mutations.

There are also other nonmedicinal methods that help treat CF symptoms, such as vest therapy, chest physical therapy, and pulmonary (heart) rehabilitation. In some cases, surgery may be required for various conditions caused by CF.

This list is a list of drugs also prescribed for CF. It is not a list of drugs recommended to take with Cayston. Ask your pharmacist or a healthcare provider if you have questions.

Frequently Asked Questions

  • What is Cayston used for?

    Cayston contains the ingredient aztreonam. It is an antibiotic that is given through the Altera nebulizer for people with CF who have lung infections caused by bacteria called Pseudomonas aeruginosa.

  • How does Cayston work?

    Cayston binds to bacteria, preventing them from growing and spreading and causing cell death.

  • What drugs should not be taken with Cayston?

    There are no known drug interactions with Cayston.

  • How long does it take for Cayston to work?

    You may start to notice an improvement in symptoms quickly. However, it is important to finish the full 28-day course of antibiotics.

    Your healthcare provider will instruct you on how to take Cayston. It is usually taken for 28 days on and then 28 days off. Follow the directions exactly so that Cayston works properly to eliminate bacteria and so you do not develop antibiotic resistance.

  • What are the side effects of Cayston?

    Common side effects include cough, stuffy nose, sore throat, fever, wheezing, stomach pain, chest discomfort, vomiting, rash, and bronchospasm.

How Can I Stay Healthy While Taking Cayston?

In addition to using medication to treat infection, there are several other things you can do to help you or your child with CF stay healthy. Your team of healthcare providers will help you develop a plan for monitoring and treating CF and its complications.

Some other tips include:

  • Avoid smoking. This includes secondhand smoke, so avoid being around others who are smoking.
  • Talk with your healthcare provider about an exercise program that is appropriate for you. Regular physical activity can help keep the airways clear and helps strengthen your bones and muscles.
  • Eat a healthy diet. You may need to eat more foods, including higher-calorie foods and foods with salt. A registered dietician can be a helpful resource in assisting you with dietary changes that can help you stay healthy, along with the medications you take.

Medical Disclaimer

Verywell Health's drug information is meant for educational purposes only and is not intended as a replacement for medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

13 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Karen Berger, PharmD
Karen Berger, PharmD, is a community pharmacist and medical writer/reviewer.