Iodine

Dermal absorption

Administrative data

Endpoint:

dermal absorption in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

publication

Title:

Povidone iodine skin absorption: an ex-vivo study.

Author:

Nesvadbova M; Crosera M; Maina G; Larese Filon F

Year:

2015

Bibliographic source:

Toxicol Lett. 2015, Jun 15; 235(3):155-60.

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

The aim of present study was to study the skin absorption of iodine after the application on the skin of povidone-iodine solution, used by health care workers during surgical procedure.

GLP compliance:

not specified

Test material

Test material information

Details on test material:

The povidone-iodine solution (10%) used in the experiments is a stable chemical complex of polyvinylpyrrolidone (povidone, PVP)
and elemental iodine (Esoform Jod 75, that contains 10% (7.5 g) of polyvinylpyrrolidone–iodine with 0.75% of active iodine; Esoform
S.P.A. Laboratorio Chimico Farmaceutico, Via del Lavoro 10, Rovigo, Italy).

Radiolabelling:

no

Test animals

Species:

other: Human abdominal full thickness skin

Administration / exposure

No. of animals per group:

For each experiment, the skin of 2 different donors, male and female, with a range of age from 50 to 70 years was used.

Details on study design:

- The experiment:
The experiments were carried out as follows:
Experiment 1: at time 0, the exposure chambers of 6 Franz diffusion cells were filled with 1.0 mL of synthetic sweat and 2.0 mL of the povidone-iodine solution (10%) providing an amount of 0.606 g cm-2 of iodine in order to ensure an infinite dose. At selected intervals (2, 4, 6, 8, 12, 20 and 24 h) 1.5 mL of the dermal bathing solution was removed and collected for the analyses. Each receptor sample was immediately replaced with an equal volume of fresh made physiological solution. At 24 h, the dermal bathing solutions were removed and stored in the freezer, the donor solutions were collected in order to verify the iodine concentration in the donor phase.
Experiment 2: experiment 1 was repeated miming the hand washing protocol used by nurses and medical doctors during surgery in Trieste Hospitals: each donor chamber has been filled with 1.0 mL of the povidone-iodine solution (10%) and the skin has been carefully washed with a cotton balls for two minutes. After that, the skin surface has been rinsed three time with 2.0 mL of physiological solution. The washing operation has been repeated twice. At selected intervals (1, 2, 4, 6, 8,12, 20 and 24 h) 1.5 mL of the dermal bathing solution was removed and collected for the analyses. Each receptor sample was immediately replaced with an equal volume of fresh made physiological solution. At 24 h, the dermal bathing solutions were removed and stored in the freezer, the donor solutions were collected in order to verify the iodine concentration in the donor phase.
Blanks: for each experiment, one cell was added as blank. The blank cells were treated as the other cells with the exception that no povidone-iodine solution (10%) has been introduced to the exposure chamber, but only synthetic sweat. As the equipment used was static, there is no relationship between the cells tested, hence each of them represents an independent evaluation.

- Analytical measurements:
ICP-MS 7500 CE Agilent Technologies Inc., Santa Clara, CA, USA instrument (with integrated autosampler) was used to determinate the total iodine concentration in the receiver phases. A five-point standard curve was used for ICP-MS measurements (0, 0.1,1,10, and 100μg/L, ion mass 127 u.m.a.). The limit of detection of iodine was 0.002μg/L and the precision of the measurements as repeatability (RSD%) for the analysis was always <2%.

Details on in vitro test system (if applicable):

- Preparation of skin membranes:
Human abdominal full thickness skin was obtained as surgical waste after the authorization of the local Ethical Committee and it was used for the absorption experiments immediately after the surgical operations. Prior to freezing, the subcutaneous fat was removed and the hair shaved with a razor. All the pieces of full
thickness skin were stored in freezer at -25℃ for a period up to, but not exceeding, two months. It has been shown that this method of storage does not damage the skin since no difference in permeability was observed between fresh and frozen segments of the same skin in a separate series of experiments.
From each skin specimen, 4 × 4 cm2 pieces were cut and mounted separately on the diffusion cells, that were previously washed the first time with freshly prepared aqua regia, the second time with diluted nitric acid, and rinsed three times with milliQ water.

Skin integrity was tested before and after each experiment using electrical conductibility by means of a conductometer (Metrohm, 660, Metrohm AG Oberdorfstr. 68 CH-9100 Herisau) operating at 300 Hz and connected to two stainless steel electrodes. The conductibility data in μS were converted into KΩcm-2. Cells with a resistance lower than 3.95 ± 0.27 KΩcm-2 were considered to be damaged and rejected.

- In vitro diffusion system:
The receptor compartment had a mean volume of 14.0 mL and was maintained at 32℃ by means of circulation of thermostated water in the jacket surrounding the cell. This temperature value was chosen in order to reproduce the hand physiological temperature at normal conditions. The solution in each cell was continuously stirred using a Teflon coated magnetic stirrer. Each piece of skin was clamped between the donor and the receptor compartment; the mean exposed skin area was 3.29 cm2 and the average membranes thickness was 0.9 mm.

Results and discussion

Any other information on results incl. tables

- Estimation of free-iodine concentration by iodine permeation assay through the skin:

The concentration of iodine in the acceptor compartment increased linearly over time in proportion to contact time between iodine and the intact skin in the donor compartment. After 24 h from the beginning of measurement the concentration in the acceptor compartment was 11.59±6.3 μg/cm2, the total amount of iodine diffusing out during this period is proportional to the total iodine absorbed by the bloodstream. The medium flux calculated was 0.73±0.33μg/cm2/h and the lag time was 8.9±1.5 h.

- Residual effect of skin iodine:

Even though the first two test tubes were marked as blank, an increased concentration of free iodine in the acceptor compartment was measured due to the presence of iodine into the skin and in synthetic sweat used in the donor phase. At approximately 8 h until it reaches the plateau.

- Influence of contact time:

After one hour an increase of iodine content that decreased over time reaching the same values of control cells. Iodine flux is dependent on contact time. The influence of contact time on free iodine flux was evaluated by applying the commercial preparation (Esoform) for 2 min and measuring the concentration of free-iodine in the receptor compartment by one-hour intervals. The obtained results clearly show that also PI that has been washed out after its application is absorbed into the bloodstream during the first hour.

Applicant's summary and conclusion

Conclusions:

After 24 h from the beginning of measurement the concentration in the acceptor compartment was 11.59 ± 6.3 μg/cm2, the total amount of iodine diffusing out during this period is proportional to the total iodine absorbed by the bloodstream. The medium flux calculated was 0.73 ± 0.33 μg/cm2/h and the lag time was 8.9±1.5 h. Povidone iodine could pass through the skin in a relevant amount.

Executive summary:

The aim of present study was to study the skin absorption of iodine after the application on the skin of povidone-iodine solution, used by health care workers during surgical procedure. Franz diffusion static cells with human skin were used. After 24 h from the beginning of measurement the concentration in the acceptor compartment was 11.59±6.3 μg/cm2, the total amount of iodine diffusing out during this period is proportional to the total iodine absorbed by the bloodstream. The medium flux calculated was 0.73±0.33 μg/cm2/h and the lag time was 8.9±1.5 h. These in vitro results confirmed that povidone iodine could pass through the skin in a relevant amount.