Phenoxybenzamine for the treatment of severe nonresponsive diarrhea in the horse.
Phenoxybenzamine, an alpha adrenergic antagonist, was administered IV to 6 clinically normal horses, 5 horses with experimentally induced diarrhea, and 7 horses with naturally-occurring diarrhea. It was established that a total of 2 mg of phenoxybenzamine/kg of body weight given in divided doses resulted in alpha adrenergic blockage of approximately 72 hours' duration, tranquilization, and mild constipation in the normal horse. The 5 experimental cases of diarrhea were involved in a laminitis research protocol in which laminitis was induced by oral carbohydrate overload. In all 5 of those cases, the severity of the diarrhea that accompanied the carbohydrate overload  was reduced. The 7 clinical cases consisted of 2 foals and 5 adults with diarrhea, some of which were nonresponsive to conventional treatment. One of the foals did not respond to the phenoxybenzamine, and the other had a questionable response, whereas the 5 adults all responded favorably to the agent. It was concluded that phenoxybenzamine has a potential place in the therapy of some cases of diarrhea that are nonresponsive to conventional therapy. The mechanism of action of phenoxybenzamine on diarrhea is not known at this time.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003967:Diarrhea / Q000188:drug therapy / Q000662:veterinary*; D005260:Female; D006734:Horse Diseases / Q000188:drug therapy*; D006736:Horses; D007263:Infusions, Parenteral / Q000662:veterinary; D008297:Male; D010643:Phenoxybenzamine / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*
D010643:Phenoxybenzamine