The toxicity and renal handling of paraquat in cynomolgus monkeys

The acute intravenous and oral toxicity of single doses of paraquat dichloride was studied in the cynomolgus monkey. Renal handling and effects upon renal function were also investigated following an oral dose of [14C]paraquat. Clinical signs consisted of vomiting, anorexia and dyspnoea. By 48 h all animals showed signs of acute renal failure with oliguria, high plasma urea and SGPT levels and metabolic acidosis. Animals dosed orally showed similar, though less severe, signs to those dosed intravenously. The oral LD50 was approx. 70 mg paraquat cation/kg. Following an oral dose plasma levels peaked by 2 h, but were constant from 12 h to 24 h. Paraquat clearance was high initially and exceeded the creatinine and urea clearance, but fell off markedly after 14 h as renal failure developed. By 18 h urine production had ceased. It is concluded that acute renal failure and acute pulmonary damage are the main causes of death, with interstitial pulmonary fibrosis being a factor in animals surviving the acute phase.