Distribution, Metabolism and Excretion of Pentachloroanisole in the Beagle Dog and Miniature Pig

Tissue distribution, excretion and metabolism studies of pentachloroanisole (PCA), an environmental metabolite of pentachlorophenol (PCP), were conducted in the beagle dog and miniature pig following single oral doses (25 mg/kg) of radiolabelled PCA. PCA was readily demethylated by both species, with a half-life of 5-8 min. The resultant PCP was the major metabolite in dogs and pigs. In the dog, an average of 21.9% of the administered radiolabel was excreted in the urine and 62.3% in the faeces during a 7-day period. Of the tissues analysed, an average of 3.2% of the radiolabel remained in the liver, and blood and muscle accounted for averages of 3.0 and 2.3%, respectively, of the dose. Free and conjugated PCP were found in the urine of dogs; no PCA or tetrachlorohydroquinone (TCH) were found. In dog faeces, PCP and a trace of polar material were observed; no PCA was excreted in dog faeces. In the miniature pig, an average of 25.8% of the administered radiolabel was excreted in the urine and 32.0% in the faeces during a 2-wk period. An average of 4.4% of the radiolabel was found in the liver, 8.8% in the blood, 7.1% in the muscle and 6.4% in the fat. In pig urine, PCP and conjugated PCP were the only metabolites observed; no PCA or TCH was found. Pig faeces contained a trace of unchanged PCA; PCP and polar metabolites were also found. Since pig tissues retained a sizeable residue 2 wk after a single dose of PCA, various agents were used in an attempt to decrease the tissue level of radiolabel in pigs; anion exchange resin was found to be the most effective.