GUAIFENESIN - CARDIOPULMONARY EFFECTS AND PLASMA-CONCENTRATIONS IN HORSES

  • 1 January 1980
    • journal article
    • research article
    • Vol. 41  (11) , 1751-1755
Abstract
The cardiopulmonary changes in horses given guaifenesin alone and in the same horses given xylazine (I.V.) immediately before administration of guaifenesin were determined. Plasma guaifenesin concentrations were determined in horses and 2 pregnant mares and compared with previously published values in ponies. The dose of guaifenesin necessary to produce lateral recumbency in adult horses was 134 .+-. 34 mg/kg (mean .+-. SD). The administration of guaifenesin caused insignificant (P < 0.05) changes in heart rate, respiratory rate, right atrial pressure, pulmonary arterial pressure and cardiac output. Systolic, diastolic and mean arterial blood pressures were significantly (P < 0.05) decreased. Arterial partial pressure of O2 (PaO2) was transiently but significantly (P < 0.05) reduced. The administration of xylazine (I.V.) to the horses before they were given guaifenesin reduced the dose of guaifenesin necessary to produce lateral recumbency to 88 .+-. 10 mg/kg. In these horses, there were significant transient decreases in heart rate, respiratory rate, cardiac output and PaO2. Central venous pressure remained significantly (P < 0.05) increased, whereas systolic, diastolic and mean arterial blood pressures were significantly (P < 0.05) decreased at all times. In horses given guaifenesin alone, plasma concentrations at the time of lateral recumbency were 313 .+-. 108 .mu.g/ml and, in those given xylazine-guaifenesin, the concentrations of the drug were 277 .+-. 83 .mu.g/ml. Neonatal concentrations of guaifenesin were .apprx. 30% of that of the mare immediately after delivery, indicating that significant amounts of guaifenesin cross the placental barrier in the mare.