Systemic Exposure & Microbiology
CAYSTON has low systemic exposure
- Mean sputum concentrations of aztreonam 10 minutes after dose administration in patients receiving CAYSTON (75 mg) 3 times a day for 28 days are shown below*:
*There was considerable variability observed between patients.
- Mean peak plasma concentrations were reached 1 hour postdose in patients receiving CAYSTON (75 mg) 3 times a day. Values shown below†:
†There was considerable variability observed between patients.
- In contrast, serum concentration following a one-time, 30-minute IV administration of aztreonam for injection (500 mg) was approximately 54 mcg/mL
- There was no systemic accumulation of CAYSTON
- Evaluation of plasma and urine aztreonam concentrations in patients following administration of CAYSTON indicated low systemic absorption of aztreonam
- About 10% of the total CAYSTON dose was excreted in the urine as unchanged drug, as compared to 60%-65% following IV administration of aztreonam for injection
CAYSTON did not negatively affect the lung microbiology profile
Resistance to CAYSTON was not increased
No changes in susceptibility of Pseudomonas aeruginosa (Pa) to aztreonam were observed following a 28-day course of CAYSTON in the phase 3, placebo-controlled trials.
In the follow‑on study of up to 18 months, cross‑resistance did not increase
No cross-resistance to other classes of antibiotics including aminoglycosides, quinolones, and beta-lactams, was observed following a 28-day course of CAYSTON in the phase 3 placebo-controlled trials or in an open-label follow-on trial of up to nine 28-day courses of 75 mg CAYSTON 3 times a day.
No trends in the treatment‑emergent isolation of other bacterial respiratory pathogens were observed in clinical trials
Burkholderia cepacia, Stenotrophomonas maltophilia, Achromobacter xylosoxidans, and Staphylococcus aureus were not observed in clinical trials. There was a slight increase in the isolation of Candida spp. following up to nine 28-day courses of CAYSTON therapy.