May 29, 2017
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Included as part of the PRECAUTIONS section.


Allergic Reactions

Severe allergic reactions have been reported following administration of aztreonam for injection to patients with no known history of exposure to aztreonam. In addition, allergic reaction with facial rash, facial swelling, and throat tightness was reported with CAYSTON in clinical trials. If an allergic reaction to CAYSTON occurs, stop administration of CAYSTON and initiate treatment as appropriate.

Caution is advised when administering CAYSTON to patients if they have a history of beta-lactam allergy, although patients with a known beta-lactam allergy have received CAYSTON in clinical trials and no severe allergic reactions were reported. A history of allergy to beta-lactam antibiotics, such as penicillins, cephalosporins, and/or carbapenems, may be a risk factor, since cross-reactivity may occur.


Bronchospasm is a complication associated with nebulized therapies, including CAYSTON. Reduction of 15% or more in forced expiratory volume in 1 second (FEV1) immediately following administration of study medication after pretreatment with a bronchodilator was observed in 3% of patients treated with CAYSTON.

Decreases in FEV1 After 28-Day Treatment Cycle

In clinical trials, patients with increases in FEV1 during a 28-day course of CAYSTON were sometimes treated for pulmonary exacerbations when FEV1 declined after the treatment period. Healthcare providers should consider a patient's baseline FEV1 measured prior to CAYSTON therapy and the presence of other symptoms when evaluating whether post-treatment changes in FEV1 are caused by a pulmonary exacerbation.

Development of Drug-Resistant Bacteria

Prescribing CAYSTON in the absence of known Pseudomonas aeruginosa infection in patients with CF is unlikely to provide benefit and increases the risk of development of drug-resistant bacteria.

Patient Counseling Information

See FDA-Approved Patient Labeling

Patients should be advised that CAYSTON is for inhalation use only and that CAYSTON should only be administered using the Altera Nebulizer System. Patients should be instructed only to reconstitute CAYSTON with the provided diluent and not mix other drugs with CAYSTON in the Altera Nebulizer System.

Patients should be advised to complete the full 28-day course of CAYSTON even if they are feeling better. Inform the patient that if they miss a dose, they should take all 3 daily doses as long as the doses are at least 4 hours apart.

Patients should be advised to use a bronchodilator prior to administration of CAYSTON. Patients taking several inhaled medications should be advised to use the medications in the following order of administration: bronchodilator, mucolytics, and lastly, CAYSTON.

Patients should be advised to tell their doctor if they have new or worsening symptoms. Patients who believe they are experiencing an allergic reaction to CAYSTON should be advised to contact their doctor immediately.

Patients should be counseled that antibacterial drugs including CAYSTON should only be used to treat bacterial infections. They do not treat viral infection (e.g., the common cold). When CAYSTON is prescribed to treat a bacterial infection, patients should be told that although it is common to feel better early in the course of therapy, the medication should be taken as directed. Skipping doses or not completing the full course of therapy may (1) decrease the effectiveness of the immediate treatment and (2) increase the likelihood that bacteria will develop resistance and will not be treatable by CAYSTON or other antibacterial drugs in the future.

Nonclinical Toxicology

Carcinogenesis, Mutagenesis, Impairment of Fertility

A 104-week rat inhalation toxicology study to assess the carcinogenic potential of aztreonam demonstrated no drug-related increase in the incidence of tumors. Rats were exposed to aztreonam for up to 4 hours per day. Peak plasma levels of aztreonam averaging approximately 6.8 mcg/mL were measured in rats at the highest dose level. This is approximately 12-fold higher than the average peak plasma level measured in humans following CAYSTON therapy.

Genetic toxicology studies performed in vitro demonstrated that aztreonam did not induce structural chromosome aberrations in CHO cells and did not induce mutations at the TK locus in mouse lymphoma L5178Y TK+/- cells. Likewise, genetic toxicology studies performed in vivo did not reveal evidence of mutagenic potential.

Aztreonam did not impair the fertility of rats when administered at doses that would provide systemic exposures far in excess of peak plasma levels measured in humans following CAYSTON therapy.

Use In Specific Populations


Pregnancy Category B

No reproductive toxicology studies have been conducted with CAYSTON. However, studies were conducted with aztreonam for injection. Aztreonam has been shown to cross the placenta and enter fetal circulation. No evidence of embryo or fetotoxicity or teratogenicity has been shown in studies with pregnant rats and rabbits. In rats receiving aztreonam for injection during late gestation and lactation, no drug induced changes in maternal, fetal or neonatal parameters were observed. These animal reproduction and developmental toxicity studies used parenteral routes of administration that would provide systemic exposures far in excess of the average peak plasma levels measured in humans following CAYSTON therapy.

No adequate and well-controlled studies of aztreonam for injection or CAYSTON in pregnant women have been conducted. Because animal reproduction studies are not always predictive of human response, CAYSTON should be used during pregnancy only if clearly needed.

Nursing Mothers

Following administration of aztreonam for injection, aztreonam is excreted in human milk at concentrations that are less than one percent of those determined in simultaneously obtained maternal serum. Peak plasma concentrations of aztreonam following administration of CAYSTON (75 mg) are approximately 1% of peak concentrations observed following IV aztreonam (500 mg). Therefore, use of CAYSTON during breastfeeding is unlikely to pose a risk to infants.

Pediatric Use

Patients 7 years and older were included in clinical trials with CAYSTON. Fifty-five patients under 18 years of age received CAYSTON in placebo-controlled trials. No dose adjustments were made for pediatric patients. Pyrexia was more commonly reported in pediatric patients than in adult patients. Safety and effectiveness in pediatric patients below the age of 7 years have not been established.

Geriatric Use

Clinical trials of CAYSTON did not include CAYSTON-treated patients aged 65 years of age and older to determine whether they respond differently from younger patients.

Use in Patients with Renal Impairment

Aztreonam is known to be excreted by the kidney. Placebo-controlled clinical trials with CAYSTON excluded patients with abnormal baseline renal function (defined as serum creatinine greater than 2 times the upper limit of normal range). Given the low systemic exposure of aztreonam following administration of CAYSTON, clinically relevant accumulation of aztreonam is unlikely to occur in patients with renal impairment. Therefore, CAYSTON may be administered to patients with mild, moderate and severe renal impairment with no dosage adjustment.

This monograph has been modified to include the generic and brand name in many instances.

Last reviewed on RxList: 11/8/2016


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