Chlorhexidine

What forms of chlorhexidine are allowed to treat organic livestock?

By Jason Stein

Chlorhexidine is a synthetic molecule that when dry appears as a pale yellow, odorless powder. It is usually dissolved at a concentration of 0.5-2% in glycerine and alcohol  when prepared for use. The National Organic Program (NOP) guidelines at §205.238(b) and (c)(2) require that synthetic drugs on the National List cannot be used in the absence of illness, and only when preventive practices and veterinary biologics are inadequate to prevent sickness. Under the NOP Rule at §205.603(a)(6) chlorhexidine is allowed for use as a teat dip when alternative germicidal agents and/or physical barriers have lost their effectiveness, and for surgical procedures conducted by a veterinarian. Chlorhexidine is believed to work as a disinfectant by disrupting the cell membranes of bacteria, resulting in cell death1.

Though it goes by a single name in the NOP Rule, this molecule has more than one allowed form, generally as different salts. The only allowed forms of chlorhexidine include: chlorhexidine, chlorhexidine diacetate, chlorhexidine gluconate, and chlorhexidine hydrochloride. This includes digluconate and dihydrochloride salts since the molecule is symmetrical and has two sites that can form a charge.

Chlorhexidine diacetate, chlorhexidine digluconate, and chlorhexidine dihydrochloride are different salt forms of chlorhexidine which are chemically stable and most biologically active within a pH range of 5-8, as noted in the 2010 Technical Advisory Panel report.

If OMRI were to review a brand name chlorhexidine product containing a form of chlorhexidine that has not been specifically identified as an allowed synthetic by the NOP, in either the NOP Rule at  §205.603(a)(6) or in a Technical Report, then OMRI would consider that form of chlorhexidine to be prohibited. Additionally, OMRI would require all excipients to be compliant with §205.603(f), which requires that excipients are identified by the FDA as Generally Recognized as Safe (GRAS), approved by the FDA as a food additive (Everything Added to Food in the United States or EAFUS), and/or included in the FDA review and approval of a New Animal Drug Application (NADA) or New Drug Application (NDA).
 
1Kuwakanond, T.; Quesnel, LB.; FEMS Microbiology Letters 1992, 79, 211-5.

Revised and updated in December 2015 by OMRI Technical Director Johanna Mirenda. This article was originally published in the Fall 2013 edition of the OMRI Materials Review newsletter.