EFFECTS OF ACEPROMAZINE MALEATE, ISOXSUPRINE HYDROCHLORIDE AND PRAZOSIN HYDROCHLORIDE ON LAMINAR MICROCIRCULATORY BLOOD-FLOW IN HEALTHY HORSES

Laser Doppler flowmetry was used to determine the effects of acepromaz ine maleate, isoxsuprine hydrochloride, and prazosin hydrochloride on laminar microcirculatory blood flow, Five adult horses, weighing 450-5 00 kg and free of evidence of laminitis or other inflammatory conditio ns of the lower limb were used, Holes were drilled on the dorsum of ea ch front hoof to the depth of the junction of the sensitive and insens itive laminae. Temperature, pulse rate and respiratory rate were obtai ned before beginning the measurements. Pulse rate was measured at 15-m inute intervals throughout the measurement period. A laser Doppler pro be was placed in each hole. Baseline Doppler flow measurements were ob tained. Following baseline determinations either acepromazine maleate (0.066 mg/kg), isoxsuprine hydrochloride (0.6 mg/kg) or prazosin hydro chloride (0.025 mg/kg) were administered intravenously, Drugs were ran domly assigned and repeated 3 times in each horse, Laminar microcircul atory blood flow was then measured continuously for 180 minutes. These data were analyzed using univariate (mixed model) repeated measures a nalysis. None of the drugs evaluated had any significant effect on lam inar microcirculatory blood flow. Acepromazine maleate, isoxsuprine hy drochloride and prazosin hydrochloride have no laminar microcirculator y blood flow effect in standing, healthy horses at dosages used. Effic acy in the use of these 3 drugs for the treatment of laminitis is ques tionable. However, this study was performed in healthy horses and the results may not be applicable in horses with laminitis.