Povidone-iodine PVP

Iodine is an essential component of thyroid hormones, and iodine deficiency can lead to severe hypothyroidism. On the other hand, excessive iodine intake also results in thyroid dysfunction in certain persons. Coindent described the first case of iodine-induced hyperthyroidism in 1821 (Fradkin and Wolff, 1983), and Hurxthal (1945) reported the first case of iodine-induced hypothyroidism. Ingestion of iodine-rich foods, such as seaweed, can cause hyperthyroidism, and the incidence of hyperthyroidism showed an increase in regions of dietary iodine deficiency after prophylactic iodization of bread or salt. Iodine-containing pharmaceuticals, such as povidone-iodine (PVP-I), radiographic contrast media and amiodarone, are a major source of excessive iodine intake (Wolff, 1969 Fradkin and Wolff, 1983 Markou et aL, 2001 Roti and degli Uberti, 2001). 

Figure 96.1 The PVP-I complex. Povidone-iodine (PVP-I), a complex of the polymer polyvinylpyrrolidone and iodine, is a water-soluble powder containing 10% iodine. The available iodine content in the preparation varies from 0.05 to 1%. PVP-I solutions used for disinfection of the skin or wounds have a 1 % iodine content.

Povidone-iodine (PVP-I, polyvinyl pyrrolidon-iodine complex, Betadine, Betaisodona, Braunol, Braunosan H, Disadine D.P., Disphex, Efo-Dine, Inadine, Isodine, Proviodine, Traumasept, Videne, CAS no. 25655-41-8). This is the most widely used iodophor and does not have the irritant properties associated with iodine solutions. At a strength of 7.5% in a surfactant base, povidone-iodine is applied as a surgical scrub, and at 4% is used as a shampoo or skin cleanser. Because of the small amounts of free iodine (less then 1 ppm in a 10% solution), antimicrobial effects are moderate in comparison with iodine solutions. 

Iodophors are complexes of iodine with a surface-active agent such as polyvinyl pyrrolidone (PVP povidone-iodine). Iodophors retain the activity of iodine. They kill vegetative bacteria, mycobacteria, fungi, and lipid-containing viruses. They may be sporicidal upon prolonged exposure. Iodophors can be used as antiseptics or disinfectants, the latter containing more iodine. The amount of free iodine is low, but it is released as the solution is diluted. An iodophor solution must be diluted according to the manufacturer s directions to obtain full activity. 

It is widely employed as a disinfectant in medicine (Povidone-iodine) because of its mildness, low toxicity, and water solubility. According to the U.S. Pharmacopeia, l ovidone-iodme is a free-flowing, brown powder dial contains from 9-12% available iodine. 11 is soluble in water and lower alcohols. When dissolved in water, the uncomplexed free iodine level is very low however, tine complexed iodine acts as a reservoir and by equilibrium replenishes the free iodine lo the equilibrium level. This prevents free iodine from being deactivated because the free form is continually available at effective biocidal levels from this large reservoir. PVP will interact with other small anions and resembles serum albumin and other proteins in this regard. It can be salted in with anions such as NaSC.N or out with NasSOa much like water-soluble proteins. 

Detection of IgE antibodies to PVP has been reported in a subject who experienced an immediate reaction that included urticaria and angio-edema following topical application of povidone-iodine, but the weak reaction, interpreted as a positive result after simple adsorption of PVP to a microtiter plate, is not entirely convincing. 

In summary, with povidone-iodine, the apparently inert substance PVP added to improve the formulation, rather than the active component, is likely to be the cause of cases of hypersensitivity occasionally seen with its use. 

Iodine solution in its earlier form without povidone (tincture of iodine) proved suboptimum for chronic treatment of open wounds because of staining of the skin, local irritation, and sensitization of skin. Experimentally, such problems are avoided with PVP-I as solubility increases and chemical reactivity decreases due to binding with povidone, A review of the safety literature evaluating PVP-I concludes there is a lack of irritation as demonstrated by skin patch tests, sensitization assays, phototoxicity and allergenicity assays in humans, and eye and dermal Draize irritation assays in rabbits [17],... 

PVP is a physiologically inert and biologically compatible polymer. PVP is known to reduce significantly the toxicity and irritant effects of many medications. PVP can form complexes with a variety of substances. For example, the PVP-iodine complex in the form of povidone or Betadine aqueous solution is the most widely used antiseptic in hospitals. It significantly reduces the toxicity and staining effect of the tincture of iodine solution but retains the germicidal activity of the iodine. 

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