Category Archives: Daily Chemistry
Povidone-iodine (PVP-I) is a stable chemical complex of polyvinylpyrrolidone (povidone, PVP) and elemental iodine. It contains from 9.0% to 12.0% available iodine, calculated on a dry basis.
This unique complex was discovered at the Industrial Toxicology Laboratories in Philadelphia by H. A. Shelanski and M. V. Shelanski. They carried out tests in vitro to demonstrate anti-bacterial activity, and found that the complex was less toxic than tincture of iodine in mice. Human clinical trials showed the product to be superior to other iodine formulations. It was first sold in 1955, and has since become the universally preferred iodine antiseptic.
PVP-I is completely soluble in cold water, ethyl alcohol, isopropyl alcohol, polyethylene glycol, and glycerol. Its stability in solution is much greater than that of tincture of iodine or Lugol’s solution.
Free iodine, slowly liberated from the poviodine-iodine (PVP-I) complex in solution, kills eukaryotic or prokaryotic cells through iodination of lipids and oxidation of cytoplasmic and membrane compounds. This agent exhibits a broad range of microbicidal activity against bacteria, fungi, protozoa, and viruses. Slow release of iodine from the PVPI complex in solution minimizes iodine toxicity towards mammalian cells.
Wound area covered in povidone-iodine. Gauze has also been applied. Povidone-iodine applied to an abrasion using a cotton swab.
Following the discovery of iodine by Bernard Courtois in 1811, it has been broadly used for the prevention and treatment of skin infections, and the treatment of wounds. Iodine has been recognized as an effective broad-spectrum bactericide, and it is also effective against yeasts, molds, fungi, viruses, and protozoans. Drawbacks to its use in the form of aqueous solutions include irritation at the site of application, toxicity and the staining of surrounding tissues. These deficiencies were overcome by the discovery and use of PVP-I, in which the iodine is carried in a complexed form and the concentration of free iodine is very low.
The product thus serves as an iodophor. In addition, it has been demonstrated that bacteria do not develop resistance to PVP-I, and the sensitization rate to the product is only 0.7% Consequently, PVP-I has found broad application in medicine as a surgical scrub; for pre- and post-operative skin cleansing; for the treatment and prevention of infections in wounds, ulcers, cuts and burns; for the treatment of infections in decubitus ulcers and stasis ulcers; in gynecology for vaginitis associated with candidal, trichomonal or mixed infections. For these purposes PVP-I has been formulated at concentrations of 7.5–10.0% in solution, spray, surgical scrub, ointment, and swab dosage forms.
It is available without a prescription under the generic name povidone-iodine or the brand name Betadine.
It is used in pleurodesis (fusion of the pleura because of incessant pleural effusions). For this purpose, povidone-iodine is equally effective and safe as talc, and may be preferred because of easy availability and low cost. 2.5% buffered PVP-I solution can be used for prophylaxis of neonatal conjunctivitis (Ophthalmia neonatorum) which can lead to blindness, especially if it is caused by Neisseria gonorrhoeae, or Chlamydia trachomatis. PVP-I appears to be very suitable for this purpose because unlike other substances it is efficient also against fungi and viruses (including HIV and Herpes simplex).
PVP-I can be loaded into hydrogels (based on carboxymethyl cellulose, poly(vinyl alcohol) and gelatin, or on crosslinked polyacrylamide). These hydrogels can be used for wound dressing. The rate of releasing of PVP-I is heavily dependent to the hydrogel composition (it grows with more CMC/PVA and descends with more gelatin).
In a clinical study of approximately 850 patients which compared the efficacy in preventing post-operative infection of pre-operative skin cleansing using chlorhexidine-alcohol vs. povidone-iodine, the rate of surgical-site infection was significantly lower in the chlorhexidine-alcohol group than in the povidone-iodine group (overall, 9.5% vs. 16.1%). Chlorhexidine-alcohol was significantly more protective than povidone-iodine against both superficial incisional infections (4.2% vs. 8.6%) and also deep incisional infections (1% vs. 3%). The incidence of organ-space infections was, however, not significantly different between the groups (4.4% vs. 4.5%). The team performing the study believes that, although both the antiseptic preparations possess broad-spectrum antimicrobial activity, the more effective protection provided by chlorhexidine-alcohol may be due to its more rapid action, its persistent activity (even when exposed to bodily fluids), and some residual effect.
Recently povidone-iodine has been incorporated into the field of nanotechnology. A wound-healing application has been developed which employs a mat of single wall carbon nanotubes (SWNTs) coated in a monolayer of povidone-iodine. It has been previously shown that the polymer polyvinylpyrrolidone (PVP, povidone) can coil around individual carbon nanotubes to make them water-soluble.This povidone-iodine coated carbon nanotube mat serves an electrically conductive bandage with antiseptics properties. Traditionally povidone-iodine is soaked into absorbant materials for application to wound sites, but this can lead to contact burns if excessive amounts of povidone-iodine are used.
Additionally, traditional methods can allow large quantities of povidone-iodine to be released from the bandage material upon contact with fluids at the wound site. Meanwhile, the carbon nanotube supported povidone-iodine is prevented from escaping from the bandage in large amounts, and after an initial release of excess povidone-iodine to the wound site, a secondary slow release of iodine from the carbon nanotube bound povidone takes place.