The pharmacology of furosemide in the horse. V. Pharmacokinetics and blood levels of furosemide after intravenous administration.

Studies were undertaken to determine blood levels of furosemide in horses after 0.5- and 1.0-mg/kg doses administered iv. Analyses indicated that the pharmacokinetic parameters were dose independent and best described by a three-compartment open model. The alpha-, beta-, and gamma-phase half-lives of 5.6, 22.3, and 158.5 min, respectively, were observed after the 0.5-mg/kg dose. Similarly, the respective half-lives after the 1.0-mg/kg dose were 5.8, 24.1, and 177.2 min. After a 0.5-mg/kg dose of furosemide, population frequency distributions were evaluated at 1 hr and 4 hr post-drug administration. At 1 hr after dosing, the blood levels of furosemide in 30 horses were normally distributed. The mean plasma level was 97.9 ng/ml with a range of 41.9 ng/ml to 155.8 ng/ml and a SD of 25.0 ng/ml. Analyses of blood levels of furosemide in 47 horses at 4 hr after drug administration indicated that the population distribution was better fit by a normal curve after log transformation of the values. The mean plasma level at 4 hr post-dosing was 9.6 ng/ml with a range of 4.0 ng/ml to 19.4 ng/ml and a SD of 3.1 ng/ml. Based on this population distribution of the plasma levels, the probability of finding furosemide plasma concentrations above 24.6 ng/ml at 4 hr after anti-epistaxis dose was estimated at less than 1 in 1000.

Chloramphenicol hemodialysis clearance.

The purpose of this study was to evaluate the dialysis clearance and plasma protein binding of chloramphenicol in a chronic renal failure patient and an acute renal/hepatic failure patient undergoing hemodialysis. Predialysis, dialysis and postdialysis plasma samples were collected and analyzed. Plasma chloramphenicol levels declined slowly during hemodialysis with measured dialysis clearance rates of 21.2 ml/min (patient C.W.) and 24.2 ml/min (patient S.T.). The protein binding of chloramphenicol, determined before and 30 min after hemodialysis, was 40 and 25% (patient C.W.) and 44 and 35% (patient S.T.), respectively. The extent to which hemodialysis removes chloramphenicol from the plasma does not appear significant enough to warrant routine dosage adjustment. The clinical significance of protein binding alterations is discussed.

Saliva, urine and plasma analysis of dyphylline via HPLC.

Improved assay methods for determination of dyphylline levels in plasma, saliva, and urine utilizing high pressure liquid chromatography have been developed. Detection of levels as low as 25 ng/ml from 0.5 ml plasma and 50 ng/ml from 0.5 ml saliva were possible. Both procedures utilized the same extraction process. A separate extraction process was used for dyphylline analysis in urine due to the presence of interferring substances occurring with previous methods. The method was applied to samples of one subjects plasma, saliva and urine after administration of dyphylline.