FDA ALERT [6/28/2007] - FDA is investigating the possible connection between the use of a liquid solution of colistimethate that was premixed for inhalation with a nebulizer and the death of a patient with cystic fibrosis (CF). The drug was prepared by a pharmacy and dispensed as prescribed in premixed unit dose ready-to-use vials. Colistimethate is used to treat Pseudomonas aeruginosa infections in the respiratory tract of patients with CF. Colistimethate is FDA approved for intravenous or intramuscular injection; it is not FDA approved for use as a liquid to be inhaled via nebulizer. However, in treating CF patients with Pseudomonas infections, colistimethate is often mixed with sterile water to form a solution just prior to inhalation via nebulizer. After mixing with sterile water and a buffer, colistimethate undergoes spontaneous hydrolysis to the bioactive form colistin. A component of colistin, polymyxin E1, is toxic to lung tissue. Premixing colistimethate into an aqueous solution and storing it for longer than 24 hours results in increased concentrations of colistin in solution, increasing the potential for lung toxicity. 

This information reflects FDA's current analysis of available data concerning this drug. Posting this information does not mean that FDA has concluded there is a causal relationship between the drug product and the emerging drug safety issue. Nor does it mean that FDA is advising practitioners to discontinue prescribing the product. FDA is considering, but has not reached a conclusion about, whether this information warrants any regulatory action. FDA intends to provide updated information when it becomes available.