antiseptic

antiseptic

[an-tuh-sep-tik]
antiseptic, agent that kills or inhibits the growth of microorganisms on the external surfaces of the body. Antiseptics should generally be distinguished from drugs such as antibiotics that destroy microorganisms internally, and from disinfectants, which destroy microorganisms found on nonliving objects. Germicides include only those antiseptics that kill microorganisms. Some common antiseptics are alcohol, iodine, hydrogen peroxide, and boric acid. There is great variation in the ability of antiseptics to destroy microorganisms and in their effect on living tissue. For example, mercuric chloride is a powerful antiseptic, but it irritates delicate tissue. In contrast, silver nitrate kills fewer germs but can be used on the delicate tissues of the eyes and throat. There is also a great difference in the time required for different antiseptics to work. Iodine, one of the fastest-working antiseptics, kills bacteria within 30 sec. Other antiseptics have slower, more residual action. Since so much variability exists, systems have been devised for measuring the action of an antiseptic against certain standards. The bacteriostatic action of an antiseptic compared to that of phenol (under the same conditions and against the same microorganism) is known as its phenol coefficient. Joseph Lister was the first to employ the antiseptic phenol, or carbolic acid, in surgery, following the discovery by Louis Pasteur that microorganisms are the cause of infections. Modern surgical techniques for avoiding infection are founded on asepsis, the absence of pathogenic organisms. Sterilization is the chief means of achieving asepsis.
Antiseptics (from Greek αντί - anti, '"against" + σηπτικός - septikos, "putrefactive") are antimicrobial substances that are applied to living tissue/skin to reduce the possibility of infection, sepsis, or putrefaction. They should generally be distinguished from antibiotics that destroy bacteria within the body, and from disinfectants, which destroy microorganisms found on non-living objects. Some antiseptics are true germicides, capable of destroying microbes (bacteriocidal), whilst others are bacteriostatic and only prevent or inhibit their growth. Antibacterials are antiseptics that only act against bacteria.

Usage in surgery

The widespread introduction of antiseptic surgical methods followed the publishing of the paper Antiseptic Principle of the Practice of Surgery in 1867 by Joseph Lister, inspired by Louis Pasteur's germ theory of putrefaction. In this paper he advocated the use of carbolic acid (phenol) as a method of ensuring that any germs present were killed. Some of this work was anticipated by:

and even the ancient Greek physicians Galen (ca 130–200 AD) and Hippocrates (ca 400 BC). There is even a Sumerian clay tablet dating from 2150 BC advocating the use of similar techniques.

But every antiseptic, however good, is more or less toxic and irritating to a wounded surface. Hence it is that the antiseptic method has been replaced in the surgery of today by the aseptic method, which relies on keeping free from the invasion of bacteria rather than destroying them when present.

How does it work?

For the growth of bacteria there must be a certain food supply, moisture, in most cases oxygen, and a certain minimum temperature (see bacteriology). These conditions have been specially studied and applied in connection with the preserving of food and in the ancient practice of embalming the dead, which is the earliest illustration of the systematic use of antiseptics.

In early inquiries a great point was made of the prevention of putrefaction, and work was done in the way of finding how much of an agent must be added to a given solution, in order that the bacteria accidentally present might not develop. But for various reasons this was an inexact method, and today an antiseptic is judged by its effects on pure cultures of definite pathogenic celicular single helix microbes, and on their vegetative and spore forms. Their standardization has been affected in many instances, and a water solution of phenol of a certain fixed strength is now taken as the standard with which other antiseptics are compared.

Some common antiseptics

  • ;Alcohols: Most commonly used are ethanol (60-90%), 1-propanol (60-70%) and 2-propanol/isopropanol (70-80%) or mixtures of these alcohols. They are commonly referred to as "surgical alcohol". Used to disinfect the skin before injections are given, often along with iodine (tincture of iodine) or some cationic surfactants (benzalkonium chloride 0.05 - 0.5%, chlorhexidine 0.2 - 4.0% or octenidine dihydrochloride 0.1 - 2.0%).
  • ;Quaternary ammonium compounds: Also known as Quats or QAC's, include the chemicals benzalkonium chloride (BAC), cetyl trimethylammonium bromide (CTMB), cetylpyridinium chloride (Cetrim, CPC) and benzethonium chloride (BZT). Benzalkonium chloride is used in some pre-operative skin disinfectants (conc. 0.05 - 0.5%) and antiseptic towels. The antimicrobial activity of Quats is inactivated by anionic surfactants, such as soaps. Related disinfectants include chlorhexidine and octenidine.
  • ;Boric acid: Used in suppositories to treat yeast infections of the vagina, in eyewashes, and as an antiviral to shorten the duration of cold sore attacks. Put into creams for burns. Also common in trace amounts in eye contact solution. Though it is popularly known as an antiseptic, it is in reality only a soothing fluid, and bacteria will flourish comfortably in contact with it.
  • ;Chlorhexidine Gluconate: A biguanidine derivative, used in concentrations of 0.5 - 4.0% alone or in lower concentrations in combination with other compounds, such as alcohols. Used as a skin antiseptic and to treat inflammation of the gums (gingivitis). The microbicidal action is somewhat slow, but remanent. It is a cationic surfactant, similar to Quats.
  • ;Hydrogen peroxide: Used as a 6% (20Vols) solution to clean and deodorize wounds and ulcers. More common 1% or 2% solutions of hydrogen peroxide have been used in household first aid for scrapes, etc. However, even this less potent form is no longer recommended for typical wound care as the strong oxidization causes scar formation and increases healing time. Gentle washing with mild soap and water or rinsing a scrape with sterile saline is a better practice.
  • ;Iodine: Usually used in an alcoholic solution (called tincture of iodine) or as Lugol's iodine solution as a pre- and post-operative antiseptic. No longer recommended to disinfect minor wounds because it induces scar tissue formation and increases healing time. Gentle washing with mild soap and water or rinsing a scrape with sterile saline is a better practice. Novel iodine antiseptics containing povidone-iodine (an iodophor, complex of povidone, a water-soluble polymer, with triiodide anions I3-, containing about 10% of active iodine) are far better tolerated, don't affect wound healing negatively and leave a deposit of active iodine, creating the so-called "remanent," or persistent, effect. The great advantage of iodine antiseptics is the widest scope of antimicrobial activity, killing all principal pathogenes and given enough time even spores, which are considered to be the most difficult form of microorganisms to be inactivated by disinfectants and antiseptics.
  • ;Mercurochrome: Not recognized as safe and effective by the U.S. Food and Drug Administration (FDA) due to concerns about its mercury content. Other obsolete organomercury antiseptics include bis-(phenylmercuric) monohydrogenborate (Famosept).
  • ;Octenidine dihydrochloride: A cationic surfactant and bis-(dihydropyridinyl)-decane derivative, used in concentrations of 0.1 - 2.0%. It is similar in its action to the Quats, but is of somewhat broader spectrum of activity. Octenidine is currently increasingly used in continental Europe as a QAC's and chlorhexidine (with respect to its slow action and concerns about the carcinogenic impurity 4-chloroaniline) substitute in water- or alcohol-based skin, mucosa and wound antiseptic. In aqueous formulations, it is often potentiated with addition of 2-phenoxyethanol.
  • ;Phenol (carbolic acid) compounds: Phenol is germicidal in strong solution, inhibitory in weaker ones. Used as a "scrub" for pre-operative hand cleansing. Used in the form of a powder as an antiseptic baby powder, where it is dusted onto the navel as it heals. Also used in mouthwashes and throat lozenges, where it has a painkilling effect as well as an antiseptic one. Example: TCP. Other phenolic antiseptics include historically important, but today rarely used (sometimes in dental surgery) thymol, today obsolete hexachlorophene, still used triclosan and sodium 3,5-dibromo-4-hydroxybenzenesulfonate (Dibromol).
  • ;Sodium chloride: Used as a general cleanser. Also used as an antiseptic mouthwash. Only a weak antiseptic effect, due to hyperosmolality of the solution above 0.9%.
  • ;Sodium hypochlorite: Used in the past, diluted, neutralized and combined with potassium permanganate in the Daquin's solution. It is now used only as disinfectant.

Negative effects

Stuart B. Levy, in a presentation to the 2000 Emerging Infectious Diseases Conference, expressed concern that the overuse of antiseptic and antibacterial agents might lead to an increase in dangerous, resistant strains of bacteria.

Endogenous

The body produces its own antiseptics, which are a part of the chemical barriers of the immune system. The skin and respiratory tract secrete antimicrobial peptides such as the β-defensins. Enzymes such as lysozyme and phospholipase A2 in saliva, tears, and breast milk are also antiseptic. Vaginal secretions serve as a chemical barrier following menarche, when they become slightly acidic, while semen contains defensins and zinc to kill pathogens. In the stomach, gastric acid and proteases serve as powerful chemical defenses against ingested pathogens.

References

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