Kinetics of gentamicin after intravenous, intramuscular, and intratracheal administration in sheep.

Kinetics of gentamicin (2.2 mg/kg of body weight) were investigated in 7 sheep after IV bolus administration. The mean serum concentration profile could be described by a 2-compartment open model with a distribution rate constant (alpha) of 3.112 +/- 1.681 hour-1 [half-life, t1/2(alpha) = 17.22 +/- 8.63 minutes] and an overall elimination rate constant (beta) of 0.485 +/- 0.028 hour-1 [t1/2(beta) - 85.87 +/- 5.03 minutes]. The apparent volume of distribution was somewhat restricted [Vd(area) = 0.194 +/- 0.059 L/Kg], and the total body clearance was 1.559 +/- 0.400 ml/kg/min. Equal dosages of gentamicin (2.2 mg/kg) were also given IM and intratracheally (IT). after IM injection, gentamicin reached peak serum concentration at postinjection minutes (PIM) 45, surpassing concentrations after the IV injection for the remainder of the experiment. The IT injection produced detectable serum concentrations at PIM 5, with a peak concentration at PIM 60. The serum drug concentrations after IT injections remained well below concentrations after IV and IM injections. Radiographic analysis of an IT injection of a gentamicin-tantalum suspension revealed good distribution throughout the trachea and proximal bronchi, with physical clearance of the tantalum occurring after greater than or equal to 10 minutes. Aspiration biopsy of the tracheal wash 6 hours after IT gentamicin injection revealed no cytologic response to gentamicin in 6 of 7 sheep, with the single response that of a purulent exudate.

Determination of blood pressure by indirect methods in dogs given acetylpromazine maleate.

This study was designed to monitor and compare indirect blood pressures by two methods (ultrasonic Doppler and photoelectric) after intravenous acetylpromazine maleate at three different doses (0.11, 0.55, and 1.10 mg/kg). Sixteen unanesthetized dogs were placed in right lateral recumbency and pressures estimated from the left hind leg at two preinjection times and at 3, 15, 60 and 120 minutes postinjection. This procedure was followed for each dog for each of the three doses. Preinjection ultrasonic mean values and standard deviations were similar to published values. Photoelectric systolic pressures were lower and diastolic pressures higher than ultrasonic systolic and diastolic pressures. The decrease in blood pressure was detected by both methods. Neither method revealed a dose related response.