title: Percutaneous absorption of topical N,N-diethyl-m-toluamide (DEET): effects of exposure variables and coadministered toxicants.
abstract: Exposure to N,N-diethyl-m-toluamide (DEET) commonly occurs in the general population and has been implicated as a contributory factor to the Gulf War Illness. The focus of the present studies was to determine the effect of coexposure factors, potentially encountered in a military environment, that could modulate transdermal flux of topically applied DEET. Factors investigated were vehicle, dose, coexposure to permethrin, low-level sulfur mustard, occlusion, and simultaneous systemic exposure to pyridostigmine bromide and the nerve agent stimulant diisopropylfluorophosphate (DFP). Studies were conducted using the isolated perfused porcine skin flap (IPPSF), with a few mechanistically oriented studies conducted using in vitro porcine skin and silastic membrane diffusion cells. DEET was quantitated using high-performance liquid chromatography. The vehicle-control transdermal DEET flux in the IPPSF was approximately 2 micrograms/cm2/h for both 7.5 and 75% DEET concentrations, a value similar to that reported in humans. DEET absorption was enhanced by coinfusion of pyridostigmine bromide and DFP, by the presence of sulfur mustard, or by dosing under complete occlusion. The greatest increase in baseline flux was fivefold. In vitro diffusion cell studies indicated that silastic membranes had two orders of magnitude greater permeability than porcine skin, and showed vehicle effects on flux that were not detected in the IPPSF. These results suggest that coexposure to a number of chemicals that potentially could be encountered in a military environment may modulate the percutaneous absorption of topically applied DEET beyond that seen for normal vehicles at typically applied concentrations.
authors.affiliation: Center for Chemical Toxicology Research and Pharmacokinetics, College of Veterinary Medicine, North Carolina State University, 4700 Hillsborough Street, Raleigh, NC 27606, USA. Jim_Riviere@ncsu.edu
authors.forename: Jim E
authors.initials: JE
authors.lastname: Riviere
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Baynes
authors.forename: James D
authors.initials: JD
authors.lastname: Brooks
authors.forename: James L
authors.initials: JL
authors.lastname: Yeatts
authors.forename: Nancy A
authors.initials: NA
authors.lastname: Monteiro-Riviere
mesh_terms: D000279:Administration, Cutaneous; D000818:Animals; D002619:Chemical Warfare Agents / Q000009:adverse effects / Q000493:pharmacokinetics*; D002851:Chromatography, High Pressure Liquid; D003671:DEET / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics*; D004347:Drug Interactions; D007302:Insect Repellents / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics*; D007531:Isoflurophate / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics; D008877:Middle East; D008889:Military Personnel; D009151:Mustard Gas / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics; D016273:Occupational Exposure; D011729:Pyridostigmine Bromide / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics; D012869:Skin Absorption; D013552:Swine; D014857:Warfare
chemical_list: D002619:Chemical Warfare Agents; D007302:Insect Repellents; D007531:Isoflurophate; D003671:DEET; D011729:Pyridostigmine Bromide; D009151:Mustard Gas