AbstractSolutions of pilocarpine, atropine and physostigmine preserved with benzalkonium, chlorhexidine, phenylmercuric nitrate (PMN), chlorocresol and chlorbutol in simple solution and in combination with either phenylethanol or disodium edetate (EDTA), were contaminated on two separate occasions with high inocula of P. aeruginosa. Phenylethanol-antibacterial combinations were consistently effective in killing the inoculum within 15 min except for one formulation with chlorhexidine and physostigmine salicylate and formulations with PMN for which sterilization times ranged from 30 to 90 min.