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Medical uses of silver

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The medical uses of silver include its incorporation into wound dressings, and its use as an antibiotic coating in medical devices. While wound dressings containing silver sulfadiazine or silver nanomaterials may be used to treat external infections.[1] Silver is also used in some medical applications, such as urinary catheters and endotracheal breathing tubes, where there is tentative evidence that it is effective in reducing catheter-related urinary tract infections and ventilator-associated pneumonia respectively.[2][3] The silver ion (Ag+
) is bioactive and in sufficient concentration readily kills bacteria in vitro. Silver and silver nanoparticles are used as an antimicrobial in a variety of industrial, healthcare and domestic applications.[4]

Colloidal silver a (colloid consisting of silver particles suspended in liquid) and formulations containing silver salts have been marketed with claims of treating a variety of diseases.[5] Colloidal silver was used by physicians in the early 20th century, but its use was largely discontinued in the 1940s following the development of antibiotics.[6][7] Since the 1990s, colloidal silver has again been marketed as an alternative medicine, often with extensive "cure-all" claims. Colloidal silver products remain available in many countries as dietary supplements and homeopathic remedies.

Medical uses

Antibacterial cream

See also: Silver sulfadiazine

A 2012 systematic review found that topical silver was equivalent to non–silver-containing ointments for burns.[8] A Cochrane systematic review from 2008 found that most of the trials had methodological shortcomings and thus are of little use.[9] Another Cochrane systematic review from 2010 concluded that "There is insufficient evidence to establish whether silver-containing dressings or topical agents promote wound healing or prevent wound infection".[1] Other reviews of the evidence have also concluded that the "quality of the trials was limited".[10] Cochrane has raised concerns about delays in time to wound healing and an increased number of dressing applications when silver sulfadiazine (SSD) is used.[9]

The US Food and Drug Administration has approved a number of topical preparations of silver sulfadiazine for treatment of second- and third-degree burns.[11]

Endotracheal tubes

Endotracheal breathing tubes coated with silver have been studied with respect to their effect on ventilator associated pneumonia. The silver coated breathing tubes reduce the incidence of VAP and delay its onset, although no benefit is seen in the duration of intubation, the duration of stay in intensive care or the mortality rate.[2][12][13]Concerns have been raised surrounding the unblinded nature of some of the studies.[2] It is unknown if they are cost effective.[14] The U.S. Food and Drug Administration in 2007 cleared an endotracheal tube with a fine coat of silver to reduce the risk of ventilator-associated pneumonia.[15]

Urinary catheters

Tentative evidence supports a decreased risk of urinary tract infections when silver-alloy catheters are used.[3][16] Their cost effectiveness is uncertain as of 2008.[16]

Anti-smoking aid

Silver acetate has been used as a potential aid to help stop smoking. A review of the literature in 2012 however found no effect of silver acetate on smoking cessation at a six month endpoint and if there is an effect it would be small.[17]

Antiseptic use

Silver compounds are used in external preparations as antiseptics, including both silver nitrate and silver proteinate, which can be used in dilute solution as eyedrops to prevent conjunctivitis in newborn babies. Silver nitrate is also sometimes used in dermatology in solid stick form as a caustic ("lunar caustic") to treat certain skin conditions, such as corns and warts.[18] Silver is also used in bone prostheses, reconstructive orthopedic surgery and cardiac devices.[19]: 17 

Adverse effects

Main article: Argyria

In animals and humans, large doses of silver salts can accumulate silver in the body.[6]: 121  Chronic intake of silver can result in an accumulation of silver or silver sulfide particles in the skin. These particles in the skin darken with exposure to sunlight, resulting in a blue or gray discoloration of the skin known as argyria.[19] Localized argyria can occur as a result of topical use of silver salt solutions, while generalized argyria results from the ingestion of silver salts.

Colloidal silver may interact with some prescription medications, reducing the absorption of some antibiotics and thyroxine among others.[20]

Some people are allergic to silver, and the use of treatments and medical devices containing silver is contraindicated for such people.[19] Although medical devices containing silver are widely used in hospitals, no thorough testing and standardization of these products has yet been undertaken.[21]

Water purification

Electrolytically-dissolved silver has been used as a water disinfecting agent, for example, the drinking water supplies of the Russian Mir orbital station and the International Space Station.[22] Many modern hospitals filter hot water through copper-silver filters to defeat MRSA and legionella infections.[23]: 29  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.[24] 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 (in this application the silver inhibits microbial growth on the filter substrate, to prevent clogging, and does not directly disinfect the filtered water).[25][26][27]

Mechanism of action

Silver and most silver compounds have an oligodynamic effect and are toxic for bacteria, algae, and fungi in vitro. The oligodynamic effect is typical for heavy metals, such as lead and mercury, but, among the elements that have this effect, silver is the least toxic for humans. The antibacterial action of silver is dependent on the silver ion.[19] 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.[19] The antibacterial action of silver has long been known to be enhanced by the presence of an electric field. Applying an electric current across silver electrodes enhances antibiotic action at the anode, likely due to the release of silver into the bacterial culture.[28] The antibacterial action of electrodes coated with silver nanostructures is greatly improved in the presence of an electric field.[29]

Alternative medicine

Since about 1990, there has been a resurgence of the promotion of the ingestion of purchased or homemade[18] colloidal silver as a dietary supplement or homeopathic remedy, marketed with claims of it being an essential mineral supplement, or that it can prevent or treat numerous diseases, such as cancer, diabetes, HIV/AIDS, herpes,[6] and tuberculosis.[18][30][31] No medical evidence supports the ingestion of colloidal silver as being effective for any of these claimed indications.[5][18][32] Silver is not an essential mineral in humans; there is no dietary requirement for silver, and no such thing as a silver "deficiency".[18] Quackwatch states that colloidal silver dietary supplements have not been found safe or effective for the treatment of anything.[33] Consumer Reports lists colloidal silver as a "supplement to avoid", describing it as "likely unsafe".[34]

There is no evidence that colloidal silver treats or prevents any medical condition, and it can cause serious and potentially irreversible side effects such as argyria.[18] In August 1999, the U.S. FDA banned colloidal silver sellers from claiming any therapeutic or preventive value for the product,[5] although silver-containing products continue to be promoted as dietary supplement in the U.S. under the looser regulatory standards applied to supplements.[5] The FDA has issued numerous Warning Letters to Internet sites that have continued to promote colloidal silver as an antibiotic or for other medical purposes.[35][36]

In 2002, the Australian Therapeutic Goods Administration (TGA) found there were no legitimate medical uses for colloidal silver and no evidence to support its marketing claims.[37] The U.S. National Center for Complementary and Alternative Medicine (NCCAM) warns that marketing claims about colloidal silver are scientifically unsupported, the silver content of marketed supplements varies widely, and ingesting colloidal silver products can have serious side effects such as argyria.[18]

In 2009, the USFDA issued a "Consumer Advisory" warning about the potential adverse effects of ingestible colloidal silver, and said that "...there are no legally marketed prescription or over-the-counter (OTC) drugs containing silver that are taken by mouth.[38]

Topical use

"A dietary supplement containing colloidal silver or silver salts may not be labeled in whole or in part for topical use. Section 201 (ff)(2)(A)(i) of the [ Federal Food, Drug, and Cosmetic Act as amended by The Dietary Supplement Health and Education Act (DSHEA) of 1994 (21 U.S.C. § 321)] requires that a dietary supplement is a product that is ‘‘intended for ingestion.’’ The term ingestion has been addressed by the federal courts in United States v. Ten Cartons, Ener-B Nasal Gel, 888 F. Supp. 393 (E.D.N.Y.), aff’d, 72 F.3d 285 (2d Cir. 1995). A topical product could not be a dietary supplement."[5]

Environmental effects

Silver that enters the environment from discarded medical sources can have detrimental effects on micro-organisms and animals (including humans).[39]

Cost

The National Health Services in the UK spent about 25 million pounds on silver-containing dressing in 2006. Silver-containing dressings represent about 14% of the total dressings used and about 25% of the overall wound dressing costs.[40]

History

Hippocrates in his writings discussed the use of silver in wound care.[41][42] At the beginning of the twentieth century surgeons routinely used silver sutures to reduce the risk of infection.[41][43] In the early 20th century, physicians used silver-containing eyedrops to treat ophthalmic problems,[44] for various infections,[45][46] and sometimes internally for diseases such as tropical sprue, epilepsy, gonorrhea, and the common cold.[7][18][47] During World War I, soldiers used silver leaf to treat infected wounds.[41][48]

Prior to the introduction of modern antibiotics, colloidal silver was used as a germicide and disinfectant.[49] With the development of modern antibiotics in the 1940s, the use of silver as an antimicrobial agent diminished.[21] Silver sulfadiazine (SSD) is a compound containing silver and the antibiotic sodium sulfadiazine, which was developed in 1968.

References

  1. ^ a b Storm-Versloot, MN (2010 Mar 17). Storm-Versloot, Marja N (ed.). "Topical silver for preventing wound infection". Cochrane database of systematic reviews (Online) (3): CD006478. doi:10.1002/14651858.CD006478.pub2. PMID 20238345. {{cite journal}}: Check date values in: |date= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  2. ^ a b c Bouadma, L (2012 Aug). "Ventilator-associated pneumonia and its prevention". Current opinion in infectious diseases. 25 (4): 395–404. doi:10.1097/QCO.0b013e328355a835. PMID 22744316. {{cite journal}}: Check date values in: |date= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  3. ^ a b Beattie, M (2011 Aug). "Silver alloy vs. uncoated urinary catheters: a systematic review of the literature". Journal of clinical nursing. 20 (15–16): 2098–108. doi:10.1111/j.1365-2702.2010.03561.x. PMID 21418360. {{cite journal}}: Check date values in: |date= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  4. ^ Maillard, Jean-Yves; Hartemann, Philippe (2012). "Silver as an antimicrobial: Facts and gaps in knowledge". Critical Reviews in Microbiology: 1. doi:10.3109/1040841X.2012.713323.
  5. ^ a b c d e Cite error: The named reference fda-rule was invoked but never defined (see the help page).
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  7. ^ a b "Colloidal silver". Memorial Sloan-Kettering Cancer Center. May 16, 2011. Retrieved January 2, 2013.
  8. ^ Aziz, Z (2012 May). "A systematic review of silver-containing dressings and topical silver agents (used with dressings) for burn wounds". Burns : journal of the International Society for Burn Injuries. 38 (3): 307–18. PMID 22030441. {{cite journal}}: Check date values in: |date= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  9. ^ a b Wasiak J, Cleland H, Campbell F (2008). Wasiak, Jason (ed.). "Dressings for superficial and partial thickness burns". Cochrane Database Syst Rev (4): CD002106. doi:10.1002/14651858.CD002106.pub3. PMID 18843629.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  10. ^ Lo SF, Hayter M, Chang CJ, Hu WY, Lee LL (2008). "A systematic review of silver-releasing dressings in the management of infected chronic wounds". Journal of clinical nursing. 17 (15): 1973–85. doi:10.1111/j.1365-2702.2007.02264.x. PMID 18705778.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  11. ^ "Drugs@FDA". Accessdata.fda.gov. Retrieved 2010-07-10.
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  16. ^ a b Schumm, K (2008 Apr 16). Schumm, Katie (ed.). "Types of urethral catheters for management of short-term voiding problems in hospitalised adults". Cochrane database of systematic reviews (Online) (2): CD004013. doi:10.1002/14651858.CD004013.pub3. PMID 18425896. {{cite journal}}: Check date values in: |date= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  17. ^ Lancaster, T (2012 Sep 12). "Silver acetate for smoking cessation". Cochrane database of systematic reviews (Online). 9: CD000191. PMID 22972041. {{cite journal}}: Check date values in: |date= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  18. ^ a b c d e f g h Cite error: The named reference nccam was invoked but never defined (see the help page).
  19. ^ a b c d e Lansdown AB (2006). "Silver in health care: antimicrobial effects and safety in use". Current Problems in Dermatology. Current Problems in Dermatology. 33: 17–34. doi:10.1159/000093928. ISBN 3-8055-8121-1. PMID 16766878.
  20. ^ Pamela L. Drake, M.P.H., National Institute for Occupational Health and Safety; Edmund Pribitkin, M.D., Thomas Jefferson University; and Wendy Weber, N.D., Ph.D., M.P.H., NCCAM (2009). "Colloidal Silver Products" (Document). U.S. Department of Health and Human Services. {{cite document}}: Unknown parameter |month= ignored (help); Unknown parameter |url= ignored (help)CS1 maint: multiple names: authors list (link)
  21. ^ a b Chopra I (2007). "The increasing use of silver-based products as antimicrobial agents: a useful development or a cause for concern?". The Journal of Antimicrobial Chemotherapy. 59 (4): 587–90. doi:10.1093/jac/dkm006. PMID 17307768. {{cite journal}}: Unknown parameter |month= ignored (help)
  22. ^ Subcommittee on Spacecraft Exposure Guidelines, Committee on Toxicology, National Research Council (2004). Spacecraft Water Exposure Guidelines for Selected Contaminants. Vol. 1. National Academies Press. p. 324. ISBN 0-309-09166-7.{{cite book}}: CS1 maint: multiple names: authors list (link)
  23. ^ Alan B. G. Lansdown (27 May 2010). Silver in Healthcare: Its Antimicrobial Efficacy and Safety in Use. Royal Society of Chemistry. ISBN 978-1-84973-006-8. Retrieved 20 January 2013.
  24. ^ Solsona, Felipe (2003). "Water Disinfection" (PDF). World Health Organization. {{cite web}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  25. ^ Richmond, Caroline (2008-10-16). "Ron Rivera: Potter who developed a water filter that saved lives in the third world". The Guardian. Retrieved 2009-05-16.
  26. ^ Corbett, Sara (December 24, 2008). "Solution in a Pot". New York Times. Retrieved May 15, 2009.
  27. ^ Committee on Creation of Science-based Industries in Developing Countries, Development, Security, and Cooperation, Policy and Global Affairs, National Research Council of the National Academies, Nigerian Academy of Science. (2007). Mobilizing Science-Based Enterprises for Energy, Water, and Medicines in Nigeria. Washington, D.C: National Academies Press. p. 39. ISBN 0-309-11118-8. {{cite book}}: |author= has generic name (help)CS1 maint: multiple names: authors list (link)
  28. ^ J. A. Spadaro, T. J. Berger, S. D. Barranco, S. E. Chapin and R. O. Becker Antibacterial Effects of Silver Electrodes with Weak Direct Current Antimicrob. Agents Chemother. 1974, 6(5):637. DOI: 10.1128/AAC.6.5.637.
  29. ^ Akhavan, Omid; Ghaderi, Elham (2009). "Enhancement of antibacterial properties of Ag nanorods by electric field". Science and Technology of Advanced Materials. 10: 015003. doi:10.1088/1468-6996/10/1/015003.
  30. ^ Wadhera A, Fung M (2005). "Systemic argyria associated with ingestion of colloidal silver". Dermatol Online J. 11 (1): 12. PMID 15748553.
  31. ^ Fung MC, Weintraub M, Bowen DL (1995). "Colloidal silver proteins marketed as health supplements". JAMA. 274 (15): 1196–7. doi:10.1001/jama.274.15.1196. PMID 7563503. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  32. ^ Newman M, Kolecki P (2001). "Argyria in the ED". Am J Emerg Med. 19 (6): 525–6. doi:10.1053/ajem.2001.25773. PMID 11593479. {{cite journal}}: Unknown parameter |month= ignored (help)
  33. ^ Edward McSweegan, Ph.D. "Lyme Disease: Questionable Diagnosis and Treatment". Quackwatch. Retrieved March, 2013. {{cite web}}: Check date values in: |accessdate= (help)
  34. ^ "Twelve supplements you should avoid". Consumer Reports. September 2010. Retrieved January 31, 2013.
  35. ^ "Colloidal Silver Not Approved". U.S. Food and Drug Administration. 2007-02-12. Retrieved 2008-09-22.
  36. ^ "FDA Warning Letter" (PDF). U.S. Food and Drug Administration. 2001-03-13. Retrieved 2008-09-22.
  37. ^ "Regulation of colloidal silver and related products". Australian Therapeutic Goods Administration. 2005-11-09. Retrieved 2008-09-22.
  38. ^ FDA Consumer Advisory. 2009. Dietary Supplements Containing Silver May Cause Permanent Discoloration of Skin and Mucous Membranes (Argyria). http://www.fda.gov/Food/DietarySupplements/Alerts/ucm184087.htm
  39. ^ ICON backgrounder: Environmental Impacts of Nanosilver, 2008
  40. ^ "Silver dressings--do they work?". Drug and therapeutics bulletin. 48 (4): 38–42. 2010. doi:10.1136/dtb.2010.02.0014. PMID 20392779.
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