CAYSTON
Clinical safety rating: caution
Comprehensive clinical and safety monograph for CAYSTON (CAYSTON).
Aztreonam is a monobactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), leading to cell lysis and death. It is active against Gram-negative aerobic bacteria including Pseudomonas aeruginosa.
| Metabolism | Aztreonam is primarily metabolized via hydrolysis of the beta-lactam ring, with minor hepatic metabolism. The metabolite is microbiologically inactive. Renal excretion accounts for approximately 60-70% of the dose as unchanged drug. |
| Excretion | Primarily renal; >99% of the absorbed dose is excreted unchanged in urine within 24 hours. No significant biliary or fecal elimination. |
| Half-life | Approximately 2.0–2.5 hours in patients with normal renal function. In patients with moderate renal impairment (CrCl 30–49 mL/min), half-life may be prolonged to ~4.5 hours. |
| Protein binding | 0–4% (negligible); does not bind significantly to plasma proteins. |
| Volume of Distribution | 0.2–0.3 L/kg; approximately 15–21 L in adults, indicating distribution primarily into extracellular fluid. |
| Bioavailability | Inhalation: ~10–15% systemic bioavailability (absorbed from the lungs). Oral: negligible (<1%). Intravenous: 100%. |
| Onset of Action | Inhalation: Peak serum concentrations are achieved by the end of the 2-3 minute nebulization. Antibacterial effect begins within minutes of exposure, though clinical improvement may take several days. |
| Duration of Action | 10–12 hours after a single dose, based on sustained drug levels in epithelial lining fluid. Dosing is every 12 hours for continuous coverage. |
75 mg (one vial) inhaled via nebulizer three times daily, each dose approximately 4 hours apart.
| Dosage form | FOR SOLUTION |
| Renal impairment | No dose adjustment required for any degree of renal impairment. |
| Liver impairment | No dose adjustment required for any degree of hepatic impairment. |
| Pediatric use | Approved for patients aged 6 years and older; weight-based dosing not required. Same adult dose of 75 mg inhaled three times daily. |
| Geriatric use | No specific dose adjustment; clinical studies included limited elderly patients, but no overall differences in safety or efficacy observed. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for CAYSTON (CAYSTON).
| Breastfeeding | It is not known whether aztreonam is excreted in human milk after inhalation. Aztreonam is excreted in milk after intravenous administration, with a milk-to-plasma ratio of approximately 0.11. Caution is advised when administering to a breastfeeding woman. Consider the developmental and health benefits of breastfeeding along with the mother's clinical need for CAYSTON. |
| Teratogenic Risk | CAYSTON (aztreonam for inhalation) is classified as FDA Pregnancy Category B. Animal reproduction studies have not demonstrated fetal risk, but there are no adequate and well-controlled studies in pregnant women. Therefore, it should be used during pregnancy only if clearly needed. No specific fetal risks by trimester have been identified, but caution is advised. |
■ FDA Black Box Warning
None.
| Serious Effects |
["Known hypersensitivity to aztreonam or any component of the formulation."]
| Precautions | ["Hypersensitivity reactions: Serious and occasionally fatal hypersensitivity (anaphylactic) reactions have been reported in patients receiving beta-lactam antibiotics. Caution in patients with a history of hypersensitivity to beta-lactams or other allergens.","Pulmonary function decline: In clinical trials, declines in FEV1 occurred more frequently in CAYSTON-treated patients. Monitor pulmonary function.","Bronchospasm: Can occur; pre-dose bronchodilator use may be considered.","Clostridioides difficile-associated diarrhea: Evaluate if diarrhea occurs.","Neurologic events: Seizures have been reported with aztreonam; caution in patients with renal impairment or CNS disorders.","Renal impairment: Dosage adjustment required for systemic administration; however, for inhaled use, systemic exposure is low, but caution is warranted."] |
| Food/Dietary | No clinically significant food interactions have been reported. Inhalation route minimizes systemic absorption; however, maintain adequate hydration. |
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| Fetal Monitoring | No specific maternal or fetal monitoring is required beyond standard obstetric care. Patients with cystic fibrosis should be monitored for pulmonary function, respiratory symptoms, and adverse reactions such as bronchospasm and hypersensitivity. |
| Fertility Effects | No studies have been conducted on the effect of CAYSTON on fertility. No adverse effects on fertility were observed in animal studies with intravenous aztreonam. |
| Clinical Pearls | CAYSTON (aztreonam for inhalation solution) is a monobactam antibiotic indicated for cystic fibrosis patients with Pseudomonas aeruginosa airway infections. Administer via PARI eFlow nebulizer only; use bronchodilator pretreatment in patients with bronchospasm. Monitor pulmonary function testing before and during therapy. Not for systemic infections. |
| Patient Advice | Use only with the PARI eFlow nebulizer; do not mix with other medications. · Store vials in refrigerator; let sit at room temperature for 30 minutes before use. · Use bronchodilator before treatment if prescribed to prevent wheezing. · Complete full course even if feeling better. · Avoid pregnancy and use effective contraception during treatment. |