Iodine medical products
This Wikipedia article gives a good, if brief, discussion of a slow-release form of iodine called "povidone-iodine" in which iodine is the only active ingredient.   


  Free iodine, slowly liberated from the povidone-iodine (PVP-I) complex
  in solution, kills eukaryotic or prokaryotic cells through iodination
  of lipids and oxidation of cytoplasmic and membrane compounds. This
  agent exhibits a broad range of microbicidal activity against
  bacteria, fungi, protozoa, and viruses. Slow release of iodine from
  the PVP-I complex in solution minimizes iodine toxicity towards
  mammalian cells.
  
  PVP-I can be loaded into hydrogels, which can be based on
  carboxymethyl cellulose (CMC), poly(vinyl alcohol) (PVA), and gelatin,
  or on crosslinked polyacrylamide. These hydrogels can be used for
  wound dressing. The rate of release of the iodine in the PVP-I is
  heavily dependent on the hydrogel composition: it increases with more
  CMC/PVA and decreases with more gelatin.