Inorganic silver salts are strongly bactericidal. Silver nitrate, 1:1000, had been most commonly used, particularly as a preventive for gonococcal ophthalmitis in newborns. Antibiotic ointments have replaced silver nitrate for this indication. Silver sulfadiazine slowly releases silver and is used to suppress bacterial growth in burn wounds (see Chapter 46).
For many years, pressurized steam (autoclaving) at 120°C for 30 minutes has been the basic method for sterilizing instruments and other heat-resistant materials. When autoclaving is not possible, as with lensed instruments and materials containing plastic and rubber, ethylene oxide—diluted with either fluorocarbon or carbon dioxide to diminish explosive hazard—has been used at 440–1200 mg/L at 45–60°C with 30–60% relative humidity. The higher concentrations have been used to increase penetration.
Ethylene oxide is classified as a mutagen and carcinogen. The OSHA permissible exposure limit (PEL) for ethylene oxide is 1 ppm calculated as a time-weighted average. Alternative sterilants now being used increasingly include vapor-phase hydrogen peroxide, peracetic acid, ozone, gas plasma, chlorine dioxide, formaldehyde, and propylene oxide. Each of these sterilants has potential advantages and problems. Automated peracetic acid systems are being used increasingly for high-level decontamination and sterilization of endoscopes and hemodialyzers because of their effectiveness, automated features, and the low toxicity of the residual products of sterilization.
Disinfectants are used as preservatives to prevent the overgrowth of bacteria and fungi in pharmaceutical products, laboratory sera and reagents, cosmetic products, and contact lenses. Multi-use vials of medication that may be reentered through a rubber diaphragm, eye drops, and nose drops require preservatives. Preservatives should not be irritating or toxic to tissues to which they will be applied, they must be effective in preventing growth of microorganisms likely to contaminate solutions, and they must have sufficient solubility and stability to remain active.
Commonly used preservative agents include organic acids such as benzoic acid and salts, the parabens, (alkyl esters of p-hydroxybenzoic acid), sorbic acid and salts, phenolic compounds, quaternary ammonium compounds, alcohols, and mercurials such as thimerosal in 0.001–0.004% concentration.
• Tinidazole: Oral; similar to metronidazole but dosed once daily; approved for trichomonas, giardiasis, and amebiasis • Methenamine hippurate and methenamine mandelate: Oral; release formaldehyde at acidic pH in the urine; used only for prophylaxis, not treatment, of urinary tract infections
Colistimethate sodium Generic, Coly-Mycin M Methenamine hippurate Generic, Hiprex Metronidazole Generic, Flagyl, Metro Nitrofurantoin Generic, Macrodantin, Macrobid
Methenamine mandelate Generic, Mandelamine
Mupirocin Generic, Bactroban, Centany
Polymyxin B (Polymyxin B sulfate) Generic DISINFECTANTS, ANTISEPTICS, & STERILANTS
Benzalkonium Generic, Zephiran
Chlorhexidine gluconate topical Generic, Hibiclens, Betasept, others
Chlorhexidine gluconate, oral rinse: 0.12% Peridex, Periogard
Iodine aqueous Generic, Lugol’s Solution
Nitrofurazone Generic, Furacin