Fate of ethion in goats after intravenous, oral and dermal administration

Toxicokinetic parameters and cumulative excretion were studied in goats after intravenous, oral and dermal administration of unlabelled and 14C-ethion. Plasma concentration-time data was subjected to non-compartmental analysis. IV injection studies showed an effective half-life (t1/2) of 2 hr, a total body clearance (ClT) of 3.21.kg-1.hr-1 and a volume of distribution (Vd(ss) of 9.4 1.kg-1. Plasma levels of 14C-ethion (ethion + metabolites) were much higher and more persistent than those of unchanged ethion. Cumulative excretion of 14C-ethion was 78% of the dose with 66% in urine, 8% in faeces and 4% in milk. Oral administration resulted in low plasma levels of unchanged ethion, an absorption half-life (t1/2 abs) of 10 hr and a bioavailability of less than 5%. Cumulative excretion was 80% of the dose with 64% in urine, 14% in faeces and 1.7% in milk. Dermal application showed a t1/2 abs of 85 hr and a bioavailability of 20%. Only 0.05% of the dose was excreted unchanged in milk. It is concluded that (1) orally administered ethion is extensively metabolized in the GIT, (2) dermal application results in prolonged and limited absorption and (3) absorbed ethion is rapidly eliminated through metabolism.