PHARMACOKINETICS AND CARDIOPULMONARY EFFECTS OF GUAIFENESIN IN DONKEYS

Five donkeys and three horses were given guaifenesin, intravenously, b y gravity administration. until recumbency was produced, The time and dose required to produce recumbency, recovery time to sternal and stan ding were recorded, Blood samples were collected for guaifenesin assay at 10, 20, 30, 40, 50, 60 min, and 2, 3, 4 and 6h after guaifenesin a dministration Serum was analysed for guaifenesin using HPLC and pharma cokinetic tic values were calculated using a computer software package (RSTRIP). In donkeys, heart and respiratory rates and blood pressures were recorded before and at 5-min intervals during recumbency, Arteri al blood samples were collected before and at 5 and 15 min intervals d uring recumbency for analysis of pH CO2, and O-2. ANOVA was used to ev aluate dynamic data, while t-tests were used for kinetic values. Respi ratory rate was decreased significantly during recumbency, but no othe r significant changes from baseline occurred, The mean (+/-SD) recumbe ncy dose of guaifenesin was 131 mg/kg (27) for donkeys and 211 mg/kg ( 8) for horses. Recovery time to sternal (min) was 15 (SE, 11) for donk eys and 34 (SD, 1.4) for horses, Time to standing was 32 min for donke ys and 36 min for horses, Calculation of AUC (area under the concentra tion-time curve) (mu g.h/mL) (dose-dependent variable) was 231 (SD, 33 ) for donkeys and 688 (SD, 110) for horses. The clearance (CL) (mL/h.k g was 546 (SL),;3) for donkeys, which was significantly different from 313 (SD, 62) for horses, Mean residence time (MRT) (h) was 1.2 (SD, 0 .1) for donkeys and 2.6 (SD, 0.5) for horses, Volume af distribution V -d(area) (mL/kg) was 678 (SD, 92) for donkeys and 794 (SD, 25) far hor ses. At the rate of administration used in this study, donkeys require d less guaifenesin than horses to produce recumbency, but cleared it m ore rapidly.