Growth of nosocomial pathogens in multiple-dose parenteral medication vials

The extent to which microbial contamination of medications dispensed in multiple-dose vials might serve as a source of infection to patients has not been fully investigated. To characterize the effects of microbial contamination, we studied the growth-supporting properties of eight medications dispensed in multiple-dose vials. Two medications, procainamide and methohexital, demonstrated no survival of any microbes 24 h after inoculation. Succinylcholine chloride, regular insulin, potassium chloride, heparin, and thiopental slowly killed or allowed limited survival of several of the microorganisms used as contaminants. Lidocaine allowed survival or proliferation of several microbial strains suspended in 0.25% peptone water in saline, but slowly killed all strains except Pseudomonas cepacia suspended in 0.9% saline. Endotoxin, measured by the Limulus amebocyte lysate assay, was found in the two medications tested, lidocaine contaminated with Pseudomonas cepacia and insulin contaminated with enterococci. Inadvertent microbial contamination of at least some parenteral medications in multiple-dose vials may result in the exposure of patients to viable organisms. The potential, however, for medications such as lidocaine to support growth of organisms under selected circumstances should be noted by those responsible for preparing and administering these drugs. The potential hazard to patients from endotoxin in contaminated medications under these circumstances has not been assessed. Additional studies of this type should be pursued to provide more complete information about the risk of microbial contamination of products for parenteral use.