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.
Department of Agriculture, Victorian Institute of Animal Science, Attwood.
P J
PJ
Huntington
S
S
Seneque
R F
RF
Slocombe
L B
LB
Jeffcott
A
A
McLean
A R
AR
Luff
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