Cayston (aztreonam for inhalation solution) is a prescription antibiotic medication used to improve respiratory symptoms in patients with cystic fibrosis who have Pseudomonas aeruginosa bacteria in their lungs. It belongs to a class of drugs known as monobactam antibiotics, which work by stopping the growth of bacteria. Cayston is specifically designed for inhalation using a nebulizer, allowing direct delivery of the medication to the lungs. This targeted approach helps to reduce the bacterial load in the respiratory tract, leading to improved lung function and reduced symptoms of infection. It is typically used in cycles of 28 days on the medication followed by 28 days off, but the specific regimen can vary based on the patient's condition and healthcare provider's recommendations.