Use of phenytoin to treat horses with Australian stringhalt.
Five horses with Australian stringhalt were treated with 15 mg/kg phenytoin orally for 2 weeks. During the second week of the trial, 3 of the horses were given an additional dose of 10 mg/kg phenytoin. The response to treatment was clinically assessed by grading the severity of the gait abnormality at the walk, trot, turning and backing twice daily. There was a significant (P less than 0.05) improvement in the gait abnormality when pre-treatment values were compared with the mean of the last 3 assessments before treatment stopped. When reassessed 2 weeks after treatment ceased, there remained a significant (P less than 0.05) improvement compared with pre-treatment values at the trot and on backing, but not at the walk or turning. Surface electromyographic recordings were made weekly from the long digital extensor muscle, and there was a change to a near normal recording by the end of treatment. Plasma phenytoin concentrations were monitored during the trial, and the dose rates used achieved a steady state with a mean plasma level of 37 +/- 7 mumol/l. There was wide variability between plasma concentrations in different horses, although there was no difference in absorption between administration of the phenytoin as a paste, or when it was mixed in the feed. Although mild tranquilization was seen after treatment, there were no clinical, haematological or biochemical signs of toxicity from the phenytoin therapy.
Huntington
P J
PJ
Department of Agriculture, Victorian Institute of Animal Science, Attwood.
Seneque
S
S
Slocombe
R F
RF
Jeffcott
L B
LB
McLean
A
A
Luff
A R
AR
D000284:Administration, Oral; D000818:Animals; D004576:Electromyography / Q000662:veterinary; D006734:Horse Diseases / Q000188:drug therapy*; D006736:Horses; D009132:Muscles / Q000503:physiopathology; D009133:Muscular Atrophy / Q000188:drug therapy / Q000662:veterinary*; D009468:Neuromuscular Diseases / Q000188:drug therapy / Q000662:veterinary*; D010672:Phenytoin / Q000008:administration & dosage / Q000097:blood / Q000627:therapeutic use*
D010672:Phenytoin