L-Tryptophan-Indol Intoxication

Johanna L. Watson • Gary P. Carlson

Experimental studies in ponies have demonstrated an acute hemolytic process associated with orally administered L-tryptophan, which is converted to indol in the GI tract.⁴ Intoxication was associated with an acute onset of restlessness, tachypnea, intravascular hemolysis, and hemoglobinuria. At necropsy there was evidence of hemoglobinuric nephrosis and bronchiolar degeneration in some ponies. Similar clinical signs were noted following oral administration of tryptophan at 0.35 to 0.60 g/kg, and indol at 0.1 to 0.2 g/kg.^4,5 Intravascular hemolysis was associated with increased osmotic fragility and with Heinz body formation in a few of the experimental ponies.