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Povidone iodine: useful for more than preoperative antisepsis
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While povidone iodine has long been used by surgeons as a preoperative antiseptic, researchers have been looking at the agent for treating viral conjunctivitis as well as other ocular diseases.
The microbicidal action spectrum of povidone iodine (PI) is broad, even after short exposure times. Further, unlike local antibiotics and other antiseptic substances, no resistance seems to develop. The high degree of bactericidal efficiency with respect to highly resistant gram-positive pathogenic micro-organisms, such as methicillin-resistant Staphylococcus aureus (MRSA) and Enterococcus strains, has made the agent particularly useful and significant for hospital hygiene.
Povidone iodine has traditionally been used by surgeons as a preoperative antiseptic. Cheaper than topical antibiotics, it is recognized as a staple solution for preparing the eye for surgery.
About 2 years ago, a stir was created when an ophthalmologist published anecdotal evidence that a brief povidone iodine eye wash in patients known to be suffering from viral conjunctivitis successfully helped to resolve the malady far faster than observation and supportive therapy alone. Since that time, investigators have been evaluating the agent to officially validate its use in this regard as well as potentially expand its role in the management of ocular disease. (Shovlin JP, Abel R. Steroids, povidone iodine recommended for adenoviral keratoconjunctivitis. Primary Care Optometry News. 2001;6(6):22-23.)
Advantages over other agents
Povidone iodine has many potential advantages over some current popular medications, including broader antibacterial spectrum, lack of identifiable bacterial resistances and significantly lower price. It has made a significant contribution to pre- and postoperative ocular surgical prophylaxis, ophthalmia neonatorum prophylaxis and treatment of bacterial conjunctivitis. (Isenberg SJ, Apt L, Campeas D. Ocular applications of povidone-iodine. Dermatology. 2002;204(suppl 1):92-95, and Editors. Ophthalmia neonatorum. Afr Health. 1995;17(5):30.)
Mechanism of action
Povidone iodine is a broad spectrum microbicide that destroys microbial protein and DNA. It has excellent in vitro antimicrobial activity and is indicated for preoperative preparation of the periocular region (lids, brow, cheek) and irrigating the ocular surface. PI is supplied as Betadine (5% sterile ophthalmic preparation solution, Alcon) and is packaged in a single-use, 1-fluid-ounce bottle.
Experimental evidence
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Researchers have compared the antibacterial effect of povidone iodine and like agents with that of ofloxacin in a rabbit inoculated with bacterial keratitis. In those reports, the researchers concluded that Betadine 0.5% demonstrated a statistically significant bactericidal effect compared with cases of staphylococcal keratitis left untreated (Melki SA, Safar A, Yaghouti F, et al. Effect of topical povidone-iodine versus topical ofloxacin on experimental staphylococcus keratitis. Graefes Arch Clin Exp Ophthalmol. 2000;238(5):459-462).
While ofloxacin had superior antibacterial effects under the conditions set forth by the study, the povidone iodine solution demonstrated superb potential. Pending improvements in its formulation for ocular maladies, it could be a formidable player in conditions such as blepharitis and microbial-induced keratitis in countries where topical antibiotics are scarce.
Studies examining the uses of povidone iodine reach back into the 1990s. Kawana and co-workers determined that PI was an effective medicine for inactivating a range of viruses, such as adenovirus, mumps, rotavirus, poliovirus (types 1 and 3), Coxsackie virus, rhinovirus, herpes simplex, rubella, measles, influenza and HIV (Kawana R, Kitamura T, Nakagomi O, et al. Inactivation of human viruses by povidone-iodine in comparison with other antiseptics. Dermatology. 1997;195(suppl 2):29-35).
In their experiments, antiseptics such as PI solution, PI gargle and PI cream, along with agents such as chlorhexidine gluconate, alkyldiamino ethylglycine HCl, benzalkonium chloride and benzethonium chloride were compared. PI was found to be effective against all the virus species tested. The PI drug products that were examined in these experiments inactivated all the viruses within a short period of time. Rubella, measles, mumps viruses and HIV were sensitive to all of the antiseptics. PI was determined to have the widest viricidal spectrum, covering both enveloped and nonenveloped viruses.
Double-masked trial
In a double-masked, controlled, prospective clinical trial involving 459 children (mean age 6.6 years with a range of 7 months to 21 years) diagnosed with acute bacterial, viral and chlamydial conjunctivitis and from Manila, Philippines, infected eyes were cultured for bacteria and underwent immunofluorescent testing for Chlamydia trachomatis. Viral conjunctivitis was diagnosed if bacterial cultures were negative and if the diagnostic criteria set forth in the study were met. Subjects were alternated to receive povidone iodine 1.25% or neomycin-polymyxin-B-gramicidin ophthalmic solution, one drop four times daily in the affected eye.
Povidone iodine 1.25% ophthalmic solution was as effective as neomycin-polymyxin B-gramicidin for treating bacterial conjunctivitis and was somewhat more effective against Chlamydia, but was ineffective against viral conjunctivitis (Isenberg SJ, Apt L, Valenton M, et al. A controlled trial of povidone-iodine to treat infectious conjunctivitis in children. Am J Ophthalmol. 2002;134(5):681-688).
Practical evidence
In the Review of Optometry 2002 Clinical Guide to Ophthalmic Drugs, Melton and Thomas present an “off-label” use of Betadine 5% solution to treat viral conjunctivitis (Melton R, Thomas RK. 2002 Clinical Guide to Ophthalmic Drugs. Supplement to Review of Optometry. 2002;139(6):40s).
After anesthetizing the eye with proparacaine solution, two drops of Betadine are instilled onto the infected ocular surface for 1 minute. A sterile saline rinse is then used to completely lavage the Betadine from the eye. Melton and Thomas report that the Betadine rinse treatment followed by a course of topical steroid drops (two to four times daily), artificial tears and cold compresses over a 1- to 3-week period can result in the expeditious resolution of the signs and symptoms of viral conjunctivitis.
Efficacy against other viruses
Evidence has also recently indicated the antiviral activity of PI against herpes simplex and adeno- and enteroviruses, as well as reaffirmed its high degree of efficiency against Chlamydia. Hence, alongside the classical fields of application, such as the disinfection of the skin and hands, mucosa antisepsis and wound treatment, explorations for additional useful indications for the substance seem to be well founded and should be encouraged. Additionally, povidone iodine ophthalmic solution should be strongly considered in the treatment of a variety of external, anterior segment diseases in developing countries where topical antibiotics are often unavailable or costly.
For Your Information:
- Marc D. Myers, OD, FAAO, is a 1999 graduate of the Pennsylvania College of Optometry. Since completing a primary care residency at the Eye Institute of the Pennsylvania College of Optometry, he has been employed as a staff optometrist in the southern New Jersey area in an ocular disease and refractive surgery practice. He can be reached at (856) 691-8188. Dr. Myers has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for the companies mentioned.
- Andrew S. Gurwood, OD, FAAO, is an associate professor of clinical sciences and an attending optometric physician at The Eye Institute of the Pennsylvania College of Optometry. He is also a member of the clinical staff in the Department of Ophthalmology at Albert Einstein Medical Center in Philadelphia. Dr. Gurwood can be reached at the Pennsylvania College of Optometry, 1200 West Godfrey Ave., Philadelphia, PA 19141; (215) 276-6134; fax: (215) 276-1329; e-mail: Agurwood@pco.edu. Dr. Gurwood has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for the companies mentioned.