Influence of inert ingredients in pesticide formulations on dermal absorption of carbaryl.
OBJECTIVE
To assess the influence of solvent plus various mixtures on percutaneous absorption and disposition of the carbamate insecticide, carbaryl (CA).


METHODS
Skin was obtained from the dorsum of 14 female weanling specific-pathogen-free Yorkshire pigs.


METHODS
In this 8-hour in vitro flow-through diffusion study, porcine skin sections were dosed with 40 micrograms of CA/cm2 of surface area, different amounts of solvents (40 or 80% acetone or dimethyl sulfoxide [DMSO]), different amounts of a surfactant (0, 1, or 5% sodium lauryl sulfate [SLS]), an insect repellent (0 or 15% diethyl-m-toluamide [DEET]), an insecticide synergist (0 or 2% piperonyl butoxide [PB]), and a CA metabolite (40 micrograms/cm2 1-naphthol [1-NA]).


RESULTS
In general, CA absorption was greater from acetone than from DMSO mixtures, and CA penetration into skin and stratum corneum was greater from DMSO at 8 hours. This is consistent with the flux-time profiles, which depicted initial peak flux within 2 to 3 hours for most acetone mixtures, but a slow increase in flux for DMSO mixtures. Irrespective of the solvent, increasing water content in pesticide dosing mixtures significantly increased CA absorption from SLS mixtures only. The SLS also enhanced CA absorption, especially at low solvent concentrations. The DEET significantly reduced CA absorption from acetone, but not from DMSO mixtures, and 1-NA enhanced CA absorption from acetone, but not from DMSO mixtures. Piperonyl butoxide significantly enhanced CA absorption from acetone and DMSO mixtures. However, addition of PB or PB plus SLS did not significantly increase CA flux above that observed from solvent plus surfactant mixtures.


CONCLUSIONS
Inert ingredients can modulate percutaneous absorption of toxicologically important pesticides and their effect or activity on CA disposition is dependent on solvent specificity and solvent concentration. Whereas SLS, PB, and 1-NA can enhance pesticide absorption, DEET can reduce absorption.
Baynes
R E
RE
Cutaneous Pharmacology and Toxicology Center, College of Veterinary Medicine, North Carolina State University, Raleigh 27606, USA.
Riviere
J E
JE
D000096:Acetone; D000818:Animals; D012721:Carbaryl / Q000008:administration & dosage / Q000493:pharmacokinetics*; D002250:Carbon Radioisotopes; D002626:Chemistry, Pharmaceutical; D004121:Dimethyl Sulfoxide; D005260:Female; D017575:Gloves, Protective; D007306:Insecticides / Q000008:administration & dosage / Q000493:pharmacokinetics*; D007840:Latex; D010882:Piperonyl Butoxide / Q000494:pharmacology; D012867:Skin / Q000166:cytology / Q000378:metabolism*; D012869:Skin Absorption / Q000187:drug effects; D012997:Solvents; D013501:Surface-Active Agents / Q000494:pharmacology; D013552:Swine
D002250:Carbon Radioisotopes; D007306:Insecticides; D007840:Latex; D012997:Solvents; D013501:Surface-Active Agents; D000096:Acetone; D010882:Piperonyl Butoxide; D012721:Carbaryl; D004121:Dimethyl Sulfoxide