Experimental 3-nitro-4-hydroxyphenylarsonic acid toxicosis in pigs.

Five times the recommended dose of 3-nitro-4-hydroxyphenylarsonic acid (187.5 mg kg-1) induces a pathognomonic clinical syndrome in pigs. The main clinical features are not continually present but are inducible only by exercise. From day 11 on the experimental diet a nervous syndrome was inducible. This manifested as muscle tremors and clonic convulsive episodes. Paraparesis developed by day 22 and paraplegia by day 33. Liver arsenic levels plateaued at 5.4 +/- 1.3 mg kg-1. The experiment confirms field observations that 3-nitro produces a characteristic toxicological syndrome, which is distinct from that of arsanilic acid. It also confirms that 3-nitro has a higher absolute toxicity than arsanilic acid in pigs as well as a lower margin of safety.