Antiseptics and disinfectants are nonselective, anti-infective agents that are applied topically. Their activity ranges from simply reducing the number of microorganisms to within safe limits of public health interpretations (sanitization), to destroying all microorganisms (sterilization) on the applied surface. In general, antiseptics are applied on tissues to suppress or prevent microbial infection. Disinfectants are germicidal compounds usually applied to inanimate surfaces. Sometimes the same compound may act as an antiseptic and a disinfectant, depending on the drug concentration, conditions of exposure, number of organisms, etc. To achieve maximal efficiency, it is essential to use the proper concentration of the drug for the purpose intended. The logic that “if a little is good, twice as much is better” is not only uneconomical but often has toxicologic implications.
Topical anti-infective agents are extensively used in surgery for antisepsis of the surgical site and surgeon’s hands and to disinfect surgical instruments, apparel, and hospital premises. Other common uses are as disinfectants for home and farm premises, food processing facilities, in water treatment, in public health sanitation, and as antiseptics in soaps, teat dips, dairy sanitizers, etc. Antiseptics also have been used to treat local infections. However, in most cases, systemic chemotherapeutic agents are preferred, because they often penetrate better into the foci of infection and are less likely than the topical anti-infectives to lose their potency when in contact with body fluids and debris in the infected area.
Ideally, antiseptics and disinfectants should have a broad spectrum and potent germicidal activity, with rapid onset and long-lasting effect. They should not be prone to development of resistance in target microorganisms. They should withstand a range of environmental factors (eg, pH, temperature, humidity) and must retain activity even in the presence of pus, necrotic tissue, soil, and other organic material. High lipid solubility and good dispersibility increase their effectiveness. Antiseptic preparations should not be toxic to the host tissues and should not impair healing. Disinfectants should be nondestructive to applied surfaces. They should be readily biodegradable, not accumulate in the environment, or react with other chemicals to produce toxic residues. Offensive odor, color, and staining properties should be absent or minimal.
Most of these compounds exert their antimicrobial effect by denaturation of intracellular protein, alteration of cellular membranes (often through extraction of membrane lipids), or enzyme inhibition. Although most classes of antiseptics and disinfectants have been in use for decades, the emergence of microbial resistance to some agents, especially in the hospital environment, has led to continued research into the development of new compounds.