title: Cardiopulmonary, behavioral, and pharmacokinetic effects of propoxyphene in horses.
abstract: The acute behavioral cardiopulmonary and pharmacokinetic effects of propoxyphene hydrochloride were studied in seven adult horses. Each horse was given three different dosages of propoxyphene (0.5, 1.0, 2.2 mg/kg) IV. Fourteen days was allotted between each drug administration. The lower IV dosages of propoxyphene (0.5, 1.0 mg/kg) resulted in no changes in indices of cardiopulmonary function. Four horses demonstrated a transient period of muscle fasciculations when given 0.5 mg of propoxyphene/kg. Horses given 1.0 mg/kg demonstrated a brief period of euphoria, ataxia, and muscle fasciculations followed by a period of increased motor activity lasting for approximately 30 minutes. Horses given 2.2 mg of propoxyphene/kg demonstrated significant (P less than 0.05) increases in heart rate and arterial blood pressure and, after a brief period of ataxia and disorientation, displayed increased motor and locomotor activity lasting several hours. These behavioral effects were less apparent in three of four horses 4 hours after their appearance by the IV administration of naloxone. Propoxyphene exhibited a dose dependent half-life of from 61 to 135 minutes and an apparent volume of distribution of from 2.54 to 4.26 L/kg. Total body clearance was 21.9-28.4 ml/min/kg. In the adult pain-free horse, propoxyphene causes dose dependent excitatory effects similar to the narcotic analgesics.
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D002319:Cardiovascular System / Q000187:drug effects*; D003672:Defecation / Q000187:drug effects; D011431:Dextropropoxyphene / Q000097:blood / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects; D006736:Horses / Q000502:physiology*; D009043:Motor Activity / Q000187:drug effects; D011651:Pulmonary Artery / Q000187:drug effects; D012119:Respiration / Q000187:drug effects*
chemical_list: D011431:Dextropropoxyphene