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What are the chemical differences between ExCel_AP^® and DuraPrep™?

Polyvinylpyrrolidone (PVP) is a polymer used in many applications.  In the first half of the 20th century, PVP was used as a blood plasma expander for trauma victims.  Today, it’s used as a binder in many pharmaceutical tablets.  It’s also used in personal care products such as shampoos, toothpastes, contact lens solutions, and hair sprays.

When combined, PVP and iodine form Povidone-Iodine (PVP-I); a water-soluble complex consisting of 10% iodine and 90% PVP.  A solution that is 10% Povidone-Iodine, in turn, contains 1% iodine “available” for killing microorganisms.  Commercially, PVP-I is commonly known under the trade name of Betadine.  Many generics now exist and based on years of use, solutions containing between 5% - 10% PVP-I (containing between 0.5% - 1% available iodine) are generally recognized by the FDA to be safe and effective for preparation of the skin prior to surgery.

ExCel_AP^® is an antiseptic formulation consisting of a combination of two active ingredients: 7.5% PVP-I (0.75% available iodine) and 72% isopropyl alcohol (IPA).  Considered by the CDC to be the “the most effective and rapid-acting skin antiseptic¹, IPA is recognized by the FDA to be safe and effective for preparation of the skin prior to surgery at concentrations between 70% and 91%.

ExCel_AP^® also contains an acrylate ingredient which is soluble in alcohol.  As the alcohol evaporates, the acrylate loses its solubility and serves to form a film on the skin which prolongs the time iodine is in contact with the skin.

DuraPrep™ is very similar to ExCel_AP^® in that it too contains PVP, iodine, isopropyl alcohol, and an acrylate.  However, the primary difference is that the PVP and acrylate molecules are in solution as a co-polymer called Povacrylex; i.e., instead of being included as separate chemical entities, the PVP and acrylate molecules are chemically bound to one another in the form of a copolymer chain.  According to the product’s label the resulting amount of “available iodine” in DuraPrep™ is 0.7% – 0.05% less than in ExCel_AP^®.

It should be noted that, as is the case with all iodine-containing antiseptics, “free iodine” is the only molecular species with a concentration proven to correlate with bactericidal activity².  In other words, while the FDA considers PVP-I and Povacrylex to be different active ingredients, both exhibit their antimicrobial properties through the release of the same chemical entity; i.e., “free iodine”.

While no data has been published directly comparing these two products, given their similar concentrations of available iodine and isopropyl alcohol, both should be expected to perform comparably in reducing the number of bacteria on the skin.

¹U.S. Centers for Disease Control and Prevention. Guideline for prevention of surgical site infection 1999. Infect Control Hosp Epidemiol 1999;20:250-278.

²Gottardi W. Iodine and iodine compounds. In: Block SS, ed. Disinfection, Sterilization, and Preservation. 5th ed. Philadelphia: Lea Febiger; 2001:159-183.

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