Silver has had some medicinal uses going back for centuries. The Phoenicians are said to have stored water, wine, and vinegar in silver bottles to prevent spoiling. In the early 1900s, people would put silver coins in milk bottles to prolong the milk's freshness. Hippocrates, the "father of medicine", wrote that silver had beneficial healing and anti-disease properties. In the early 1900s, silver gained regulatory approval as an antimicrobial agent. Prior to the introduction of antibiotics, colloidal silver was used as a germicide and disinfectant. Physicians used it as an eyedrop for ophthalmic problems, for various infections, and sometimes internally for diseases such as tropical sprue, epilepsy, gonorrhea, and the common cold. Colloidal silver preparations (CSP) were used to treat or prevent "gonorrhea and gonorrheal conjunctivitis. Although silver products were infrequently promoted for oral use, benefits have been even more questionable."With the introduction of antibiotics in the 1940s, the use of silver as an antimicrobial agent diminished.
The today medical uses of silver include its incorporation into wound dressings to treat external infections, and its use as an antiseptic and disinfectant in medical appliances. Silver is also promoted within alternative medicine in the form of colloidal silver, although its use is controversial.
The silver ion (Ag+) is bioactive and in sufficient concentration readily kills bacteria in vitro. Silver also kills bacteria in external wounds in living tissue and therefore physicians use wound dressings containing silver sulfadiazine (Ag-SD) or silver nano-materials to treat external infections. Wound dressings containing silver are increasing in importance due to the recent increase of antibiotic-resistant bacteria such as methicillin-resistant Staphylococcus aureus. The disinfectant properties of silver are used in medical applications, such as urinary catheters and endotracheal breathing tubes, where the silver content is effective in reducing incidences of catheter-related urinary tract infections and ventilator-associated pneumonia (VAP) respectively. Silver is also used in bone prostheses, reconstructive orthopaedic surgery and cardiac devices, as well as on surfaces and fabrics to reduce the spread of infection.
Since the 1990s, "colloidal silver", a liquid suspension of microscopic silver particles, has been marketed as an alternative medicine, often claiming impressive "cure-all" qualities. The effectiveness of these products has never been scientifically proven, and in some jurisdictions it is currently illegal to include such claims in product advertisements. Medical authorities and publications advise against the ingestion of colloidal silver preparations, because of their lack of proven effectiveness and because of the risk of adverse side-effects, such as argyria. Historically, colloidal silver was also used as an internal medication to treat a variety of diseases. Their use was largely discontinued in the 1940s, due to the development of safe and effective modern antibiotics and concern about adverse side-effects.
Medical Applications of Silver
Antiseptic: Silver and silver compounds have an oligodynamic effect and are toxic for bacteria, algae, and fungi in vitro. The oligodynamic effect is typical for heavy metals like lead and mercury, but, among the elements that have this effect, silver is the least toxic for humans. It is established that the antibacterial action of silver is dependent on the silver ion. The effectiveness of silver compounds as an antiseptic is based on the ability of the biologically active silver ion (Ag+) to irreversibly damage key enzyme systems in the cell membranes of pathogens. It has long been known that the antibacterial action of silver is enhanced by the presence of an electric field. Applying a few volts of electricity across silver electrodes drastically enhances the rate that bacteria in solution are killed. It has been discovered that the antibacterial action of silver electrodes is greatly improved if the electrodes are covered with silver nanorods.
Disinfectant: Electrolytically dissolved silver has been used as a water disinfecting agent. Silver was added as a disinfectant to the drinking water supplies of Russian Mir orbital station and the International Space Station. The World Health Organization includes silver in a colloidal state produced by electrolysis of silver electrodes in water, and colloidal silver in water filters as two of a number of water disinfection methods specified to provide safe drinking water in developing countries. Along these lines, a ceramic filtration system coated with silver particles has been created by Ron Rivera of Potters for Peace and used in developing countries for water disinfection.
External infections: Wound dressings containing silver are increasing in importance due to the increase of antibiotic-resistant bacteria, which has imposed clinical limits on the use of antibiotics. Topical silver is regaining popularity in the management of open wounds, due largely to the spread of methicillin-resistant Staphylococcus aureus and the resultant reduction in first-line antibiotic prescribing”, and that “Some silver-based dressings appear to provide an effective alternative to antibiotics in the management of wound infection. Silver has proven antimicrobial activity that includes antibiotic-resistant bacteria. It has a broad spectrum of antimicrobial activity, with minimal toxicity toward mammalian cells at low concentrations, and has a less likely tendency than antibiotics to induce resistance due to its activity at multiple bacterial target sites.
Medical appliances: The disinfectant properties of silver are used in some other medical applications, such as catheters and endotracheal breathing tubes. A study on the use of silver-alloy catheters by the University of Michigan School of Medicine concluded that “The data supporting the use of silver alloy urinary catheters to reduce urinary catheter-related bacteriuria is reasonably strong.” The study also concluded that silver alloy catheters are more effective than standard catheters for reducing bacteriuria in adults in hospital having short-term catheterization, and that, although they cost about $6 more than standard urinary catheters, they may be worth the extra cost, since catheter-related infection is a common cause of nosocomial infection and bacteremia. Related meta-analysis also clarified discrepant results among earlier trials of silver-coated urinary catheters by revealing that silver alloy catheters are significantly more effective in preventing urinary tract infections than are silver oxide catheters. These conclusions are supported by, among others, studies by the University Hospitals Leuven, Belgium and the University Hospital for Anesthesiology and Surgical Intensive Care, Halle, Germany.
Alternative medicine: From approximately 1990, there has been a resurgence of the promotion of colloidal silver as an alternative medicine treatment, marketed with claims of it being an essential mineral supplement, or that it can prevent or treat numerous diseases like cancer, diabetes, HIV/AIDS, and herpes, as well as tuberculosis. Silver is not an essential mineral in humans; there is no dietary requirement for silver, and no such thing as a silver "deficiency". There is no medical evidence that colloidal silver is effective for any of these claimed indications.
Adverse Health Effects
The risk expected due to clinical exposure to silver is "minimal", as only chronic ingestion or inhalation of silver preparations leads to an accumulation of silver in the human body that can cause argyria, argyrosis (accumulation of silver in the eye), and other conditions. Silver-based products are contra-indicated for people who are allergic to silver. The reference dose, published by the United States Environmental Protection Agency in 1991, which recommends the estimated daily exposure that is unlikely to incur a appreciable risk of deleterious effects during a lifetime, is 5 µg/kg/d; meaning 5 micrograms of silver per kilo of weight per person each day – about 1 liter of 10 ppm colloidal silver per month for a 66 kg person. An article from the National Center for Complementary and Alternative Medicine points out that silver nitrate and silver sulfadiazine can have negative side-effects, and that they must be applied to the body externally and not taken internally.
However, the chronic intake of silver products and the silver buildup from colloidal silver can result in an accumulation of silver or silver sulfide particles in the hair, skin, kidneys, liver, heart and muscles due to high methionine-containing proteins, such as keratin, myosin, tropomyosin, troponin, and key dieptide glutathione. There have been isolated reports of serious neurologic (such as seizures), renal, or hepatic complications, as well as headaches, stomach distress, fatigue, and skin irritation. if ingested, colloidal silver may react with certain drugs, such as Penicillamine, thyroxine, quinolones, and tetracyclines. One death has been reported in the medical literature which the authors felt was due to silver toxicity resulting from repeated oral ingestion of colloidal silver. Colloidal silver can reduce the absorption of some medications, including tetracycline and quinolone antibiotics and can bind to penicillamine, thereby reducing the effectiveness of those medications.
For more information: http://en.wikipedia.org/wiki/Medical_uses_of_silver
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