Antiseptic

Antiseptics (from Greek ἀντί - anti, '"against" + σηπτικός - sēptikos, "putrefactive" ) are antimicrobial substances that are applied to living tissue/skin to reduce the possibility of infection, sepsis, or putrefaction. Antiseptics are generally distinguished from antibiotics by the latter's ability to be transported through the lymphatic system to 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 have the proven ability to act against bacteria. Microbicides which destroy virus particles are called viricides or antivirals.

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:


 * Dr. George H. Tichenor who experimented with the use of alcohol on wounds ca. 1861–1863, and subsequently marketed a product for this purpose known as "Dr. Tichenor's Patent Medicine" after the American Civil War.
 * Ignaz Semmelweis who published his work The Cause, Concept and Prophylaxis of Childbed Fever in 1861, summarizing experiments and observations since 1847.
 * Florence Nightingale, who contributed substantially to the report on the Royal Commission on the Health of the Army (1856–1857), based on her earlier work.
 * Oliver Wendell Holmes, Sr., who published The Contagiousness of Puerperal Fever in 1843.

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.

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

In early inquiries, there was much emphasis on the prevention of putrefaction, and procedures were carried out to find how much of an agent must be added to a given solution in order to prevent development of undesirable bacteria. However, for various reasons, this method was inaccurate, and today an antiseptic is judged by its effect on pure cultures of defined pathogenic celicular single helix microbes and their vegetative and spore forms. The standardization of antiseptics has been implemented in many instances, and a water solution of phenol of a certain fixed strength is now used as the standard to 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.


 * Brilliant Green: A triarylmethane dye still widely used as 1% ethanol solution in Eastern Europe and ex-USSR countries for treatment of small wounds and abscesses. Efficient against gram-positive bacteria.


 * 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% (20 Vols) solution to clean and deodorize wounds and ulcers. More common 3% 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 comparatively 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 negatively affect wound healing, and leave a deposit of active iodine, thereby creating the so-called "remnant," or persistent, effect. The great advantage of iodine antiseptics is their wide scope of antimicrobial activity, killing all principal pathogens 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).


 * Manuka Honey: Recognized by the U.S. Food and Drug Administration (FDA) as a medical device for use in wounds and burns. Active +15 is equal to a 15% solution of phenol.


 * 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 boric acid in Dakin's solution. (See Microcyn below.)


 * Calcium hypochlorite: Used by Semmelweis, as "chlorinated lime", in his revolutionary efforts against childbed fever.


 * Sodium bicarbonate (NaHCO3): has antiseptic and disinfectant properties.


 * Terpenes: are the main type of compound found in essential oils, and some have reasonably strong antibacterial, antifungal and antiviral properties. For example Terpinen-4-ol is found in Tea tree oil.


 * Microcyn: is a compound of water, sodium chloride (0.023%), sodium hypochlorite (0.004%), and hypochlorous acid (0.003%). It became approved for sale on U.S. markets in June 2011. It is neutral in ph, stingless, and tasteless. It does not injure normal tissue. It is effective against a wide variety of organisms from MRSA and other bacteria to fungi, viral disease forms such as HIV, and some spores.

Evolved resistance

 * See also Antibiotic resistance, Multiple drug resistance

By continued exposure to significant levels of antiseptics or antibiotics, bacteria can evolve to the point where they are no longer harmed by these compounds.

Different antiseptics differ in how they cause bacteria to evolve, which leads to genetic defenses against particular compounds. It can also be dose dependent; resistance can occur at low doses but not at high; and resistance to one compound can sometimes increase resistance to others.

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.