PHARMACODYNAMICS Silver exhibits a broad-spectrum antimicrobial activity. Silver ions were shown to mediate an effective antibacterial action against _Streptococcus mutans_, one of major bacteria present in the human oral cavity and one of etiological microorganism of dental caries [A33141]. A study reported a dose-dependent antimicrobial activity of silver nanoparticles against MRSA and non-MRSA bacteria [A33140]. Silver nanoparticles were also shown to mediate antibacterial activity against Gram-positive _S. aureus_ and Gram-negative _E. coli_ by inhibiting the growth [A33142]. ; ; In experimental dinitrochlorobenzene-induced inflammatory models in porcine or murine skin, topical application of silver nitrate and nanocrystalline silver were shown to exert anti-inflammatory effects associated with lymphocyte apoptosis, decreased expression of pro-inflammatory cytokines, and reduced gelatinase activity [A33138]. In a rat model of ulcerative colitis, orally or intracolonically administered nanocrystalline silver were shown to suppress matrix metalloproteinase (MMP-9), tumour necrosis factor (TNF), and interleukin-β (IL-β) and IL-12 [A33138].

TOXICITY Acute oral LD50, acute dermal LD50, and acute inhalation LD50 for 4 hours in rat are >5000 mg/kg, >2000 mg/kg, and >5.16 mg/m^3, respectively [MSDS]. ; ; While individuals experiencing mild to moderate silver toxicity remain asymptomatic, chronic inhalation has been associated with mild chronic bronchitis and rare cases of exposure to large amounts of silver have been associated with symptoms of peripheral neuropathy, decreased mental status, and seizures [L2853]. Argyria is a detoxification mechanism for excess silver where the body sequesters and deposits excess silver in the blood vessels and connective tissue to render it in the form of silver protein complexes or silver sulphide [A33141, L2853]. The development of argyria through occupational exposure is reported to be a slow process [L2853]. While argyria does not cause significant pathological damage in any tissue [A33138], heavy deposition of insoluble silver precipitates can cause discoloration or blue-grey darkening of the eyes, nasal septum, throat, skin, and other internal organs following repeated exposure [L2853]. Signs from prolonged intake of low doses of silver compound may include fatty degeneration of the liver and kidneys, and changes in blood cells [A33141]. Silver may cause metal fume fever, and colloidal silver preparations are known to exert harmful effects in humans [L2853].