Particulate contamination of local anesthetic solutions

Particulate contamination was found in one particular lot number of local anesthetic, lidocaine with 1:100,000 epinephrine. The contaminants were noticed in several cartridges of each container and varied in size from minute to several millimeters. Analysis of the foreign matter revealed the particles to be of a way or puttylike consistency; however, the sterility of the solution was not altered and the pH was still within acceptable limits. The contaminant was most likely wax or a combination of wax, silicone, and glycerin, which are constituents of the rubber stopper and its associated lubricants. This problem was most likely due to temperature changes during storage and shipment, but it was also possibly due to manufacturing discrepancies.