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Oral and Dermal Pharmacokinetics of Triclopyr in Human VolunteersDow Chemical Company Ltd, Agricultural Products R&D, Letcombe Regis, Oxfordshire, OX12 9JT, UK
Dow Chemical. Company, Toxicology Research Laboratory, 1803 Building, Midland, Michigan, 48674, USA
Dow Chemical Company Ltd, Agricultural Products R&D, Letcombe Regis, Oxfordshire, OX12 9JT, UK
CTC (International) Ltd, 30-33 Townfield St, Chelmsford, Essex, CM1 1QL, UK
Charterhouse CRU Ltd, 91-93 Charterhouse St, London, EC1M 6HR, UK
Blood levels and urinary excretion of triclopyr, the active ingredient in Garlon® herbicides, were followed in six volunteers given single oral doses of 0.1 and 0.5 mg/kg body weight. Five of these volunteers later received dermal applications of Garlon 4 herbicide formulation equivlant to 3.7 mg triclopyr/kg body weight applied to the forearm. Following oral administration blood levels peaked at 2-3 h and declined to undetectable levels within 48 h; more than 80% of. the dose was found as unchanged triclopyr in the urine. A two-compartment pharmacokinetic model was used to describe the time-course of triclopyr clearance; half-lives for the rapid initial and slower terminal phases were 1.3 h and 5.1 h respectively, and were independent of dose. Due to the slow half-life for dermal absorption (t
Human & Experimental Toxicology, Vol. 8, No. 6,
431-437 (1989) |
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= 16.8 h) the rapid initial elimination phase was obscured and the pharmacokinetics could be simplified by a one-compartment model. An average of 1.37% of the applied dose was recovered in the urine; when corrected for recovery after oral administration this was equivalent to an absorption of 1.65%. Triclopyr is slowly absorbed through skin and is rapidly eliminated. It has very low potential to accumulate in man or to be absorbed through the skin in acutely toxic amounts.