What the label lists and what reports show
Aztreonam side effects
Aztreonam's FDA label lists its adverse reactions in its own words. FAERS holds 7,147 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is infective pulmonary exacerbation of cystic fibrosis (849 reports).
- Generic listed
Check it at the source: the aztreonam FDA label on DailyMed (effective June 3, 2024, Hospira, Inc.); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of CAYSTON?CAYSTON may cause serious side effects, including: Severe allergic reactions. Stop your treatment with CAYSTON and call your healthcare provider right away if you have any symptoms of an allergic reaction, including: Rash or swelling of your face Throat tightness Trouble breathing right after treatment with CAYSTON (bronchospasm). Tell your healthcare provider right away if you get any of these symptoms of bronchospasm with using CAYSTON: shortness of breath with wheezing coughing and chest tightness To decrease the chance of this happening, be sure to use your inhaled bronchodilator medicine before each treatment with CAYSTON. See "How should I take CAYSTON?" The most common side effects of CAYSTON include: cough nasal congestion wheezing sore throat fever. […]
Source: FDA drug label (Cayston), Gilead Sciences, Inc., effective December 1, 2025 (SPL set 67300ca3-8c53-4ce4-8e86-2c03be1f9b8a), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsLocal reactions such as phlebitis/thrombophlebitis following intravenous administration, and discomfort/swelling at the injection site following intramuscular administration occurred at rates of approximately 1.9% and 2.4%, respectively. Systemic reactions (considered to be related to therapy or of uncertain etiology) occurring at an incidence of 1% to 1.3% include diarrhea, nausea and/or vomiting, and rash. Reactions occurring at an incidence of less than 1% are listed within each body system in order of decreasing severity: Hypersensitivity –anaphylaxis, angioedema, bronchospasm Hematologic –pancytopenia, neutropenia, thrombocytopenia, anemia, eosinophilia, leukocytosis, thrombocytosis Gastrointestinal –abdominal cramps; rare cases of C. difficile –associated diarrhea, including pseudomembranous colitis, or gastrointestinal bleeding have been reported. …
Table 1 Adverse Reactions Reported in more than 5% of Patients Treated with CAYSTON in the Placebo-Controlled Trials
This table is printed in the Cayston label published by Gilead Sciences, Inc. of December 1, 2025; the label quoted above does not print one.
| Event (Preferred Term) | Placebo (N=160) n (%) | CAYSTON 75 mg 3 times a day (N=146) n (%) |
|---|---|---|
| Cough | 82 (51%) | 79 (54%) |
| Nasal congestion | 19 (12%) | 23 (16%) |
| Wheezing | 16 (10%) | 23 (16%) |
| Pharyngolaryngeal pain | 17 (11%) | 18 (12%) |
| Pyrexia | 9 (6%) | 19 (13%) |
| Chest discomfort | 10 (6%) | 11 (8%) |
| Abdominal Pain | 8 (5%) | 10 (7%) |
| Vomiting | 7 (4%) | 9 (6%) |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
Source: FDA drug label, Hospira, Inc., effective June 3, 2024 (SPL set d4500795-3b07-4a7d-b432-73cafbb3dbc6), via openFDA; the full label on DailyMed
What do FAERS reports show?
7,147 reports list aztreonam among the medicines taken, each a report of something that happened, not proof the medicine caused it; 978 are coded as a death and 3,574 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Reports rose sharply in 2019 (1,221, against a median of 397 a year): FAERS counts follow reporting, which news, litigation and label changes can drive, not how often a reaction happens. Of the 18 reactions below, 9 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Aztreonam: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions