title: Effects of phenytoin in two myotonic horses with hyperkalemic periodic paralysis.
abstract: The effects of phenytoin treatment were evaluated in 2 myotonic horses with hyperkalemic periodic paralysis (HPP). Phenytoin treatment abolished the clinical signs of muscle fasciculations following oral potassium challenge and decreased or abolished repetitive firing and myotonic discharges found on electromyographic examination. In both horses, an abnormally low threshold for calcium-induced calcium release was measured in heavy sarcoplasmic reticulum fractions from skeletal muscle, and this threshold increased with phenytoin treatment. Results suggest phenytoin is useful in modifying disordered ion regulation in the sarcolemma and sarcoplasmic reticulum of skeletal muscle in equine hyperkalemic periodic paralysis.
authors.affiliation: Department of Clinical Studies, University of Pennsylvania, School of Veterinary Medicine, Kennett Square 19348.
authors.forename: J
authors.initials: J
authors.lastname: Beech
authors.forename: J E
authors.initials: JE
authors.lastname: Fletcher
authors.forename: L
authors.initials: L
authors.lastname: Tripolitis
authors.forename: S
authors.initials: S
authors.lastname: Lindborgh
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D004576:Electromyography / Q000662:veterinary; D006734:Horse Diseases / Q000188:drug therapy / Q000235:genetics*; D006736:Horses; D006947:Hyperkalemia / Q000188:drug therapy / Q000662:veterinary*; D008297:Male; D009132:Muscles / Q000187:drug effects / Q000378:metabolism; D010245:Paralyses, Familial Periodic / Q000188:drug therapy / Q000662:veterinary*; D010672:Phenytoin / Q000627:therapeutic use*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism
chemical_list: D010672:Phenytoin; D002118:Calcium