Subacute toxicity of pyridoxine hydrochloride in the beagle dog

Abstract

Supplemental doses of 0, 50, or 200 mg of pyridoxine HCl/kg/day were administered po to three groups of dogs for an average of 107 days. Ataxia, muscle weakness, and loss of balance developed between 40 and 75 days of treatment in the group that received 200 mg/kg/day. Clinical signs of toxicity were not observed in the 50-mg/kg/day dose group. Histologic examination of the tissues in the animals receiving the highest dose revealed bilateral loss of myelin and axons in the dorsal funiculi (f. cuneatus and f. gracilis) and loss of myelin in individual fibers of the dorsal nerve roots. In the group receiving 50 mg/kg/day pathological damage was limited to a bilateral loss of myelin in the dorsal nerve roots. Serum glutamic oxaloacetic transaminase and creatine phosphokinase activities were greater and cholesterol concentrations were decreased in the serum of animals receiving 200 mg/kg/day at the termination of the study. Analyses of tissues for pyridoxine concentrations revealed elevated values in the blood, cerebral cortex, spinal cord, spleen, kidney, and muscle in the group receiving 200 mg/kg/day. The group receiving 50 mg/kg/day had elevated pyridoxine values only in blood and cerebral cortex.