Pharmacotherapeutic group: Ophthalmologicals; anti-infectives
ATC code: S01AX18
Broad-spectrum antiseptic, bactericidal, virucidal and fungicide.
Antiseptic group: Halogen oxidant (iodophore).
Mechanism of action
Povidone iodine is an iodophore that has an established use as a broad-spectrum antiseptic, mainly for the treatment of contaminated wounds and for the preoperative preparation of the skin, mucous membranes and the ocular surface. The organic complex contains approximately 10% of active available iodine.
Its spectrum of activity is iodine which gradually and slowly released exerts:
- bactericidal effect in less than 5 minutes in vitro, for all bacteria,
- fungicide effect for yeasts and filamentous fungi.
Solutions of povidone iodine gradually release iodine to exert an antimicrobial effect against bacteria, fungi, viruses, and spores. Although povidone iodine is less potent than preparations containing free iodine, it is also less toxic.
Organic materials (proteins, serum and blood) reduce the activity of free iodine, the active form of the medicinal product. Iodophores are unstable at alkaline pH.
Pharmacodynamic effects
Povidone iodine is a complex of the polymer polyvinylpyrrolidone (povidone) with iodine which, after application, continues to deliver iodine to the ocular surface over the short time that the solution is in contact with the eye.
After application, exposure of the ocular surface to iodine arises from the presence of free iodine in solution, and iodine bound to the polymer, which serves as a reservoir. As the preparation comes in contact with the eye, more and more iodine dissociates from the polymer.
Mechanisms of resistance
There are no reports of bacterial cross-resistance to antibiotics arising from exposure to povidone iodine, or iodine, or of co-resistance due to any known genetic linkage of resistance determinants.
There are limited reports of contamination of iodophores with Pseudomonas species, in nutrient restricted environments, such as hospital waste water, indicating that resistance to povidone-iodine can occur. However, this is of limited relevance to the use of povidone iodine in ocular antisepsis.