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Ronald E. Baynes, DVM, PhD

Ron Baynes

Pharmacology and Risk Assessment

Office: D-343, CVM Main Building
Phone: 919.513.6261
Fax: 919.513.6358

Course Involvement

Graduate Courses

Undergraduate Courses


Center for Chemical Toxicology Research and Pharmacokinetics

FARAD (Food Animal Residue Avoidance Databank)

Research Area

Dermal Absorption Assessment

Skin represents a significant surface area over which humans and animals may be exposed to hazardous chemicals. Occupational exposure to hazardous chemicals via skin can result in local effects (e.g., irritant dermatitis) or systemic toxicity. Unfortunately, workers are not exposed to a single chemical, but rather chemical mixtures and therefore quantitative risk assessment in any work place scenario should take this into account. The focus of my research is to determine physiochemical and chemical-biological interactions in epidermal corneocytes and intercellular lipids in the epidermis that can influence dermal absorption of complex mixtures.

Dermal Absorption

Identification of these interactions in in vitro flow-through porcine skin and inert membranes and ex vivo porcine skin models allows one to predict mixture effects on the dermal disposition of hazardous chemicals in human skin. Because porcine skin is physiologically and biochemically similar to human skin, chemical transport mechanisms are comparable and reduces uncertainty in the risk assessment process.

Current research activities are focused on assessing the dermal disposition of cutting fluid and jet fuel additives and pesticides. This research is providing some understanding of the physicochemical factors influencing dermal absorption of these pesticides and formulation additives that cause occupational irritant dermatitis. Other work is focused on understanding transdermal delivery of avermectins across skin various food animal species. HPLC and GC analytical methods are continually being developed.

pharmacokinetics data

Residue Pharmacology and Risk Assessment of Veterinary Drugs:

FARAD is a multi-institutional project funded in part by the North Carolina State University, University of Florida, and University of California and the US Department of Agriculture (USDA).

The mission of FARAD is to maintain a drug and chemical database that can be used to prevent harmful residues from occurring in livestock products. Livestock farmers, veterinarians, extension personnel and related government specialist consult with FARAD to determine what drugs are approved for use in livestock and what are safe levels and safe withdrawal times for approved and unapproved/accidental use. The ultimate aim is to utilize relevant regulatory and pharmacokinetic data to provide farmers and veterinarians with food safety information so that they can produce meat and milk free of residues and reduce the risk of the public from being exposed to contaminated food.

Current Research and Extension Activities are focused on providing expert consultation to veterinarians and livestock farmers about drug/chemical residues in livestock, development of algorithms for estimating safe withdrawal times, development of provisional acceptable residues as temporary safe levels in animal-derived food, and development of residue monitoring and residue avoidance programs internationally (gFARAD). The laboratory has been active in HPLC analytical method development for antibiotic residues in milk.

Selected Publications

Leavens, T., Tell, L., Waltman, L., Shelver, W., Wu, H., Wagner, S., Baynes RE., Smith, G., and Riviere, JE. (2014). Development of a Physiologically Based Pharmacokinetic Model for Flunixin in Cattle (Bos Taurus). Food Addit. Contaminants. (in press).

Li, M., Gehring, R., Tell, L., Baynes, R., Huang, Q., and Riviere, J. (2014). Interspecies mixed effect pharmacokinetic modeling of penicillin G in cattle and swine. Antimicrob. Agent. Chemother. (in press).

Howard JT*., Baynes, RE. Brooks, JD., Yeatts, JL., Bellis, B., Ashwell, MS., Routh, P., O’Nan, AT., and Maltecca, C. (2014). The effect of breed and sex on sulfamethazine, enrofloxacin, fenbendazole and flunixin meglumin pharmacokinetic parameters in swine. J. Vet Pharmacol. Therap (in press).

Kissell*, L., Leavens, T., Baynes, RE., Riviere, JE., Smith, G (2014).  Comparison of flunixin pharmacokinetics and milk elimination in healthy cows and cows with mastitis. J. Amer. Vet. Med Assoc. (in press).

Lindquist* D., Wu H, Mason S, Yeatts J, Brooks J, Barlow B, Schill K, Baynes R. (2014). Tetracycline residues in porcine stomach after administration via drinking water on a swine farm. J Food Prot. 2014 Jan;77(1):122-6. doi: 10.4315/0362-028X.JFP-13-199

Wu* H, Baynes RE, Tell LA, Riviere JE. (2013). Prediction of flunixin tissue residue concentrations in livers from diseased cattle. Food Chem Toxicol. 62:876-879.

Kissell*, LW, Baynes RE., Riviere, JE., and Smith GW. (2013). Occurrence of flunixin residues in bovine milk samples from USA. Food Addit. Contam. Vol. 00, No.00, 1-4,    

Xu* G, Hughes-Oliver JM, Brooks JD, Baynes RE. (2013). Predicting Skin Permeability from Complex Chemical Mixtures: Incorporation of an Expanded QSAR Model. SAR QSAR Environ Res. 24(9):711-731.

Shelver WL, Tell LA, Wagner S, Wetzlich SE, Baynes RE, Riviere JE, Smith DJ. (2013). Comparison of ELISA and LC-MS/MS for the Measurement of Flunixin Plasma Concentrations in Beef Cattle after Intravenous and Subcutaneous Administration. J Agric Food Chem. 2013 Mar 7. [Epub ahead of print],

Xu* G, Hughes-Oliver JM, Brooks JD, Yeatts JL, Baynes RE. (2013). Selection of appropriate training and validation set chemicals for modeling dermal permeability by U-optimal design. SAR QSAR Environ Res., 24(2):135-156

Wu* H, Baynes RE, Leavens T, Tell LA, Riviere JE (2012). Use of population pharmacokinetic modeling and Monte Carlo simulation to capture individual animal variability in the prediction of flunixin withdrawal times in cattle. J Vet.  Pharmacol.  Ther.   36(3):248-257.

Kissell* LW, Smith GW, Leavens TL, Baynes RE, Wu H, Riviere JE. (2012). Plasma pharmacokinetics and milk residues of flunixin and 5-hydroxy flunixin following different routes of administration in dairy cattle. J Dairy Sci. 2012 Oct 3. pii: S0022-0302(12)00734-5. doi: 10.3168/jds.2012-5754.

*Mason, SE., #Baynes, RE., Almond, and Riviere JE. (2012). Variables important to the population pharmacokinetic modeling of tetracycline water medication in swine. Am. J. Vet. Res. 73(10):1641-9 .

Romanet J, Smith GW, Leavens TL, Baynes RE, Wetzlich SE, Riviere JE, Tell LA. (2012). Pharmacokinetics and tissue elimination of tulathromycin following subcutaneous administration in meat goats. Am J Vet Res. 73(10):1634-40

Leavens, T., Tell, L. A., Clothier, K. A., Griffith, R. W., Baynes, R. E., and Riviere, J. E. (2012). Development of a physiologically based pharmacokinetic model to predict tulathromycin distribution in goats. J Vet. Pharmacol. Therap. 35(2): 121-131.

Clothier, KA., Leavens, T., Griffith, RW., Wetzlich, SE., Baynes, RE., Riviere, JE., Tell, LA. (2012). Tulathromycin assay validation and tissue residues after single and multiple subcutaneous injections in domestic goats (Capra aegagrus hircus). J. Vet Pharm. Therap., 35(2):113-120.

Clothier, K.A., Leavens, T.L., Griffith, R.W., Wetzlich, S.E., Baynes, R.E., Riviere, J.E., & Tell, L.A. (2011). Pharmacokinetics of tulathromycin after single and multiple subcutaneous injections in domestic goats (Capra aegagrus hircus). J Vet. Pharmacol. Therap. doi: 10.1111/j.1365-2885.2010.01261.x. [Epub ahead of print].

*McPhee, C., Anderson, KL., Barlow, B., Yeatts., J., Mason, SE., and #Baynes, RE. (2011). Milk and plasma disposition following intramammary administration of a phytoceutical mastitis treatment. J. Dairy. Sci. 94(4): 1738-1743.

*Mason SE, #Baynes RE., Almond GW, and Scheidt AB. (2011). Stability and bioactivity of tetracycline water medication in swine production units. J. Swine .Health Prod. 19(2): 107-111.

#Baynes RE., Barlow B., Mason, S.E., and Riviere JE. (2010). Disposition of melamine residues in blood and milk from dairy goats. Food Chem. Toxicol.  48(8-9):2542-2546.

*Young G, Smith GW., Tell., LA.., Leavens TL., Wetzlich SE., Mason SE., Baynes RE. (2010). Pharmacokinetics of tulathromycin following subcutaneous administration in meat goats. Res. Vet Sci. cleardoi:10.1016/j.rvsc.2010.06.025

*Vijay V., #Baynes RE., Young S., and Riviere JE. (2009). Selection of appropriate training set of chemicals for modeling dermal permeability using uniform coverage design. QSAR & Combinatorial Sci. 28(11-12): 1478-1486 .

*Mason, SE., #Baynes, RE., Almond, GW., Riviere JE., and Scheidt, AB. (2009). Pharmacology of tetracycline water medication in swine. J. Anim. Sci. 87(10):3179-3186.

*Vijay, V., White, EM., Kaminski, MD., Riviere, JE., and #Baynes, RE. (2009). Dermal permeation of biocides and aromatic chemicals in three generic formulations of metal working fluids. J. Toxicol. Environ. Health. 72(13):832-841.

Dorr, P., Nemechek, M., Almond, G.; Scheidt, A., Baynes, RE., Gebreyes, WA., (2009). Pharmacoepidemiology of water flow variation and pharmaceutical delivery in swine finishing facilities. J. Am Vet Med. Assoc. 235(3):299-304.

Smith, GW., Davis, JL., Baynes, RE., Yeatts, JL., Barlow, BM., and Riviere, JE. (2009). Elimination kinetics of tilmicosin following intramammary administration in lactating dairy cattle. J. Am. Vet. Med. Assoc. 234(2):245-248 .

*Buur, JL., #Baynes, RE., Smith, GW., and Riviere, JE. (2009). A physiologically-based pharmacokinetic model linking plasma protein binding interactions with drug disposition. Res. Vet Sci. 86(2):293-301 .

#Baynes, RE, Xia, XR., *Vijay, V., and Riviere, J. (2008). A solvatochromatic approach to quantifying formulation effects on dermal permeability. SAR QSAR Environ Res 19(7-8): 615-630.

Buur JL, Baynes RE, Riviere JE: Estimating meat withdrawal times in pigs exposed to melamine contaminated feed using a physiologically based pharmacokinetic model. Regulatory Toxicology and Pharmacology 51: 324-331, 2008.

Yeatts JL, Baynes RE, Xia XR, Riviere JR: Application of linear salvation energy relationships to a custom-made polyaniline solid-phase microextraction fiber and three commercial fibers. Journal of Chromatography A 1188: 108-117, 2008.

Mason SE, Baynes RE, Buur JL, Riviere JE, Almond GW: Sulfamethazine water Medication Pharmacokinetics and Contamination in a Commercial Pig Production Unit. Journal of Food Protection 71: 584-589, 2008.

Baynes RE, Xia XR, Imran M, Riviere JE: Quantification of Chemical Mixture Interactions Modulating Dermal Absorption Using a Multiple Membrane Fiber Array. Chem. Res. Toxicol. 21: 591-599, 2008.

Ardente AJ, Barlow BM, Burns P, Goldman R, Baynes RE: Vehicle effects on in vitro transdermal absorption of sevoflurane in the bullfrog, Rana catesbeiana. Environmental Toxicology and Pharmacology: 25: 373-379, 2008.

Baynes RE, Smith G, Mason SE, Barrett E, Barlow BM, Riviere JE: Pharmacokinetics of melamine in pigs following intravenous administration. Food and Chemical Toxicology 46: 1196-1200, 2008.

Monteiro-Riviere NA, Baynes RE, Riviere JE: Animal Skin Morphology and Dermal Absorption. In Dermal Absorption and Toxicity Assessment. (Eds. MS Roberts and KA Walters). 2nd ed, Informa Healthcare, New York, NY, Chapter 2, 17-35, 2008.

Riviere JE, Xia XR, Baynes RE. Membrane coated fiber (MCF) array approach for predicting skin permeability of chemical mixtures from different vehicles. Toxicol. Sci. 99: 153-161, 2007.

Xia XR, Baynes RE, Monteiro-Riviere NA, Riviere JE: A system coefficient approach for quantitative assessment of the solvent effects on membrane absorption from chemical mixtures. SAR QSAR Environmental Research 18(5): 579-593, 2007.

Needham ML, Webb AI, Baynes RE, Riviere JE, Craigmill AL, Tell LA: Current update on drugs for game bird species. Journal of the American Veterinary Medical Association 231: 1506-1508, 2007.

Baynes RE, Xia XR, Barlow BM, Riviere JE: Partitioning Behavior of Aromatic Components in Jet Fuel into Diverse Membrane-coated Fibers. Journal of Toxicology and Environmental Health 70: 1879-1887, 2007.

Vijay V, Yeatts JL, Riviere JE, Baynes RE: Predicting dermal permeability of biocides in commercial cutting fluids using a LSER approach. Toxicology Letters 175:34-43, 2007.

Xia XR, Baynes RE, Monteiro-Riviere NA, Riviere JE: An experimentally based approach for predicting skin permeability of chemicals and drugs using a membrane-coated fiber array. Toxicology and Applied Pharmacology 221: 320-328, 2007.

Monteiro-Riviere NA, Inman AO, Barlow BM, Baynes RE: Dermatotoxicity of cutting fluid mixtures: In vitro and in vivo studies. Cutaneous and Ocular Toxicology 25: 235-247, 2006.

Kong XQ, Shea D, Baynes RE, Riviere JE, Xia XR: Regression method of the hydrophobicity ruler approach for determining octanol/water partition coefficients of very hydrophobic compounds. Chemosphere 2006.

Willens S, Stoskopf MK, Baynes RE, Lewbart GA, Taylor SK, Kennedy-Stoskopf S: Percutaneous malathion absorption by anuran skin in flow-through diffusion cells. Environmental Toxicology and Pharmacology 22: 255-262, 2006.

Willens S, Stoskopf MK, Baynes RE, Lewbart GA, Taylor SK, Kennedy-Stoskopf S: Percutaneous malathion absorption in the harvested perfused anuran pelvic limb. Environmental Toxicology and Pharmacology 22: 263-267, 2006.

Buur JL, Baynes RE, Smith G and Riviere JE: Pharmacokinetics of flunixin meglumine in swine after intravenous dosing. Journal of Veterinary Pharmacology and Therapeutics 29: 437-440, 2006.

Buur J, Baynes RE, Smith G and Riviere J: Use of probabilistic modeling within a physiologically based pharmacokinetic model to predict sulfamethazine residue withdrawal times in edible tissues in swine. Antimicrobial Agents and Chemotherapy 50: 2344-2351, 2006.

Baynes RE, Buur JL: Chemical Risk Assessment. In Biological Concepts and Techniques in Toxicology, (Ed. JE Riviere), Taylor and Francis, Chapter 7, pp. 93-116, 2006.

Gehring R, Baynes RE, Riviere JE: Application of risk assessment and management principles to the extralabel use of drugs in food-producing animals. Journal of Veterinary Pharmacology and Therapeutics 29: 5-14, 2006.

Baynes RE: Gulf War Syndrome: Risk Assessment Case Study. In Dermal Absorption Models in Toxicology and Pharmacology, (Ed. JE Riviere), CRC Press, Taylor and Francis Group, New York, NY. Chapter 9, pp.59 -176, 2006.

Xia XR, Baynes RE, Riviere JE: A Novel System Coefficient Approach for Systematic Assessment of Dermal Absorption from Chemical Mixtures. In Dermal Absorption Models in Toxicology and Pharmacology, (Ed. JE Riviere), CRC Press, Taylor and Francis Group, New York, NY. Chapter 5, p.71 88, 2006.

Van der merwe D, Brooks JD, Gehring R, Baynes RE, Monteiro-Riviere NA, Riviere JE: A physiological-based pharmacokinetic model of organophosphate dermal absorption. Toxicological Sciences , 188-204, 2006.

Baynes RE, Brooks JD, Barlow BM, Riviere JE: NDELA and nickel modulation of triazine disposition in skin. Toxicology and Industrial Health, 197-205, 2005.

Baynes RE, Yeatts JL, Brooks JD, Riviere JE: Pre-treatment effects of trichloroethylene on the dermal absorption of the biocide, triazine. Toxicology Letters 159: 252-260, 2005.

Buur JL, Baynes RE, Craigmill AL, Riviere JE: Development of a physiologic-based pharmacokinetic model for estimating sulfamethazine concentrations in swine and application to prediction of violative residues in edible tissues. American Journal of Veterinary Research 66: 1686-1693, 2005.

Xia XR, Baynes RE, Monteiro-Riviere NA, Riviere JE: Membrane uptake kinetics of jet fuel aromatic hydrocarbons from aqueous solutions studied by a membrane-coated fiber technique. Toxicology Mechanisms and Methods 15: 307-316, 2005.

Buur JL,Baynes RE, Yeatts JL, Davidson G, DeFrancesco TC: Analysis of diltiazem in Lipoderm(r) transdermal gel using reversed-phase high-performance liquid chromatography applied to homogenization and stability studies. Journal of Pharmaceutical and Biomedical Analysis 38:60-65, 2005.

Muhammad F, Monteiro-Riviere NA, Baynes RE, Riviere JE: Effect of in vivo jet fuel exposure on subsequent in vitro dermal absorption of individual aromatic and aliphatic hydrocarbon fuel constituents. Journal of Toxicology and Environmental Health 68:719-737, 2005.

Gehring R, van der Merwe D, Pierce A, Baynes RE, Craigmill A, Riviere JE: Multivariate meta-analysis of pharmacokinetic studies of ampicillin trihydrate in cattle. American Journal of Veterinary Research 66:108-112, 2005.

Xia, XR, Baynes RE, Monteiro-Riviere NA, Riviere JE: Determination of the partition coefficients in a lipophilic membrane/water system by using a membrane-coated fiber technique. European Journal of Pharmaceutical Sciences 24:15-23, 2005.