Main content area

Metabolism of pyriproxyfen in rats. 1. Absorption, disposition, excretion, and biotransformation studies with [phenoxyphenyl-14C]pyriproxyfen

Matsunaga, H., Yoshino, H., Isobe, N., Kaneko, H., Nakatsuka, I., Yamada, H.
Journal of agricultural and food chemistry 1995 v.43 no.1 pp. 235-240
pyriproxyfen, insect growth regulators, oral administration
Male and female rats were given a single oral dose of [phenoxyphenyl-14C]pyriproxyfen [4-phenoxyphenyl (R,S)-2-(2-pyridyloxy)propyl ether] at 2 (low dose) or 1000 (high dose) mg/kg. 14C was rapidly excreted into feces and urine, with the former route predominating (about 90% of the dose). Peak 14C concentrations in blood, kidney, liver, and other tissues except for fat occurred 2 - 8 h after administration, being 0.4, 0.4, 2.5, and <0.2 microgram of pyriproxyfen equivalents/g of tissue (ppm), respectively. Peak 14C concentration in fat occurred 12-24 h after administration, being 0.3 - 0.5 ppm. 14C tissue residues on the seventh day were below 0.02 and 10 ppm for the low and high doses, respectively. The major metabolic reactions were hydroxylation at the 2- or 4-position of the terminal phenyl ring, hydroxylation at the 5-position of the pyridyl ring, cleavage of the ether linkages, and conjugation of the resultant phenols with sulfuric acid. No marked sex-related differences were observed for 14C excretion or 14C tissue residues. However, a slight sex-related variation was found for the extent of metabolic reactions.