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Here it says on povidone-iodine:

"Route of Elimination: Povidone-Iodine is intended for topical application and is not eliminated"

"Clearance: Povidone-Iodine is intended for topical application and is not eliminated"

"Metabolism: Povidone-Iodine is not absorbed or metabolised"

Now Povidone-Iodine is a very widespread antiseptic used directly on open wounds and there are cases of people using it as a disinfectant before and after microneedling (ie: inducing micro-injuries with a dermaroller device over the skin) which ensures penetration of the substance through the skin and blood circulation and into the body.

What happens with it once it's inside the body - even if some is excreted what happens with the rest which isn't? does it forever lingers within the body (cells, liver etc)?

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Your source (DrugBank via PubChem) is describing the typical pharmacokinetic information (ADME, absorption, distribution, metabolism, excretion) on Providine-Iodine, under the assumption it is not absorbed. It's true, a thing that is not absorbed has no volume of distribution, is not metabolized, and is not eliminated.

Though Providine-Iodine is not absorbed as is, Iodine is.

From the Lexicomp drug information for prescribers:

Absorption: Absorbed systemically as iodine; amount depends upon concentration, route of administration, characteristics of skin

Other pharmacokinetic properties are as for Iodine. It may be taken up by the thyroid. Clearance is primarily unchanged (as Iodine) by the kidney.

The absorption through the skin as iodine and elimination by the kidneys are the reasons for the prescribing precautions:

  • Use with caution in patients with burns (excess absorption)
  • Use with caution in patients with renal impairment (impaired excretion)
  • Use with caution in patients with thyroid disorders (taken up by the thyroid)

This case report of Iodine toxicity following prolonged povidone iodine administration is available on pubmed central. It's from the 80s, but it is still relevant and the comments section has a good overview:

The reports of iodine absorption from topical povidoneiodine solution suggest that absorption is enhanced when the compound is applied to denuded skin, mucosal surfaces with high absorptive capacity or extensive areas of intact skin. The evidence for iodine absorption includes documented serum iodine concentrations and thyroid function abnormalities.

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  • $\begingroup$ I see, it wasn't understood from the text I've quoted that these claims were under the assumption that the Povidone-Iodine is not absorbed. I don't have access to the Lexicomp info so two questions: 1. I guess my original question concerns the PVP compound - what happens with the PVP that isn't excreted? (question continues in the following comment) $\endgroup$ – Amit Jul 2 '18 at 18:54
  • $\begingroup$ On the PVP page it says that: "THE RETENTION OF PVP IN THE BODY IS PROPORTIONAL TO ITS MOLECULAR SIZE, SINCE ONLY THAT OF LOW MOLECULAR WEIGHT CAN BE EXCRETED. THE RETICULOENDOTHELIAL SYSTEM RETAINS PVP WITH A MOLECULAR WEIGHT IN EXCESS OF 110,000" so does it mean it lingers forever in the cells of the body (possibly liver)? 2. I know that Iodine is metabolized but does this necessarily imply that the povidone-iodine molecule is? $\endgroup$ – Amit Jul 2 '18 at 18:55
  • $\begingroup$ @Amit none of my references are able to measure any absorption of the polyvinyl polymer, just the iodine (released by PVP). The question of excretion vs. retention in the reticuloendothelial system is one of metabolism and excretion, or excretion unchanged. Theoretically, if you were able to absorb a high molecular weight polyvinyl polymer somehow, it wouldn't be excreted unchanged by the kidney (because it wouldn't be filtered by the glomerulus. It would have to be metabolized by the liver first, which would break it down into something that would be excreted by the kidney. $\endgroup$ – De Novo Jul 2 '18 at 19:17
  • $\begingroup$ @Amit the point here is that it's the Iodine that people are/have been worried about (as far as the toxicity of PVP-Iodine is concerned). It's the iodine that is absorbed, and it's the iodine that is (potentially) toxic. $\endgroup$ – De Novo Jul 2 '18 at 19:20
  • $\begingroup$ @Amit is there a particular reason you're interested in the idea that the polymer would accumulate and be retained forever in the liver? $\endgroup$ – De Novo Jul 2 '18 at 19:21

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