Polyvidone (povidone) iodine

Healthy skin

Repeated surgical skin antisepsis and hand washing did not increase serum iodine concentrations, but produced a small increase in iodine content in the 24-hour urine [ ].

Burns

The use of povidone iodine for the treatment of burns, for peritoneal lavage in the treatment of purulent peritonitis, or as a rinsing solution for body cavities can increase serum iodine concentrations associated with increased urinary excretion of iodine. In people with burns, the extent of iodine absorption depends on the extent of the burned body surface. It is not uncommon for serum iodine concentrations to rise to more than 1000 μg/ml. If renal function is intact, iodine elimination in the urine can be adequate. The serum iodine concentration returns to normal about 1 week after the last application.

The penetration of povidone iodine has been studied in vivo in rabbits [ ]. The penetration from third-degree burns on the back was measured autoradiographically in tissues, blood, urine, and bandages. The results showed that about 20% of iodine is absorbed through fresh necrosis, whereas only 5% is absorbed through a clean wound or 24-hour-old necrosis. The passage through burn necrosis was faster than through vital tissue.

In repeated topical use on burns, the extent of absorption seems to decrease with the treatment time.

Wounds

Povidone iodine inhibits leukocyte migration and fibroblast aggregation in wounds. The effect on the wound healing process has been studied in 294 children undergoing surgery, 283 of whom had undergone appendectomy [ ]. In a first series using 5% povidone iodine aerosol for preoperative disinfection, the postoperative wound infection rate was 19% in the test group and only 8% in the controls. When a 1% povidone iodine solution was used, only 2.6% of the patients were infected (control group 8.5%). Using a drain with a cellulose viscose sponge, 5% povidone iodine by aerosol inhibited leukocyte migration, but no cell aggregates or fibroblasts were detected. A 5% solution allowed better cellular movement and attachment to the framework, polymorphonuclear leukocytes predominating. The excipients in the aerosol formula must be more toxic to the cell than those in the solution. If a 1% povidone iodine solution was absorbed by the sponge, the aggregation phenomenon was only slightly averted and cell morphology was similar to that of the saline control.

Povidone iodine reduced the number of wound infections only in patients with appendicitis in whom neither peritonitis nor a periappendicular abscess had yet developed [ ].

Mucous membranes

The effect of a povidone iodine mouthwash on thyroid function has been studied in 16 medically healthy volunteers [ ]. After they had used the mouthwash four times daily for a period of 14 days, all thyroid tests were significantly changed, but there was no suppression of thyroid function. However, this was not to be expected, considering the short test period.

Body cavities

When povidone iodine is used as a rinsing solution in body cavities, absorption of the whole macromolecular complex is possible. The complex has a molecular weight of about 60 000 and cannot be eliminated by the kidneys or metabolically. It is filtered by the reticuloendothelial system [ ].

Although povidone iodine is no longer used in dialysates, a povidone iodine-containing cap is used to seal the Tenckhoff catheter during the day. Iodine-induced hypothyroidism occurred in a 3-year-old boy and an 18-month-old girl, in both cases due to the sealing cap [ ]. The povidone iodine inside the cap diffused into the catheter and flushed into the peritoneal cavity at the next dialysis session.

Intravaginal administration

Systemic iodine absorption can occur after intravaginal administration of povidone iodine [ ]. There were increases in serum iodine, protein-bound iodine, and inorganic iodine, but not serum thyroxine, after a 2-minute vaginal administration of povidone iodine in non-pregnant women [ ].