PHARMACOKINETICS OF GENTAMICIN AT STEADY-STATE IN PONIES - SERUM, URINE, AND ENDOMETRIAL CONCENTRATIONS

  • 1 January 1985
    • journal article
    • research article
    • Vol. 46  (6) , 1268-1271
Abstract
Gentamicin (GT) [antiinfective drug] was administered i.m. to 6 healthy mature mare ponies at a dosage of 5 mg/kg of body weight every 8 h for 7 consecutive days (total, 21 doses). Two venous blood samples were collected before (trough) and at 1 h (peak) after the 5th, 10th, 14th, and 19th doses. An endometrial biopsy was done of each mare on days 4 and 7. On the 7th day, just before the 21st administration of GT, base-line blood samples were collected, and 22 blood samples were collected over a period 48 h after GT was given. The mares were catheterized on the 7th day and urine was collected for 24 h. Serum, urine, and endometrial GT concentrations were determined by a radioimmunoassay technique (sensitivity of 0.3 .mu.g/ml of serum). Serum GT concentration data obtained from the terminal phase were best fitted by a 1-compartment open model with a biological half-life of 2.13 .+-. 0.43 h. Total body clearance and renal clearance were 1.69 .+-. 0.11 and 1.40 .+-. 0.26 ml/min per kg, respectively. Mean endometrial concentrations on day 4 and day 7 were 5.02 .+-. 3.3 and 12.75 .+-. 1.6 .mu.g/g. To achieve mean serum GT concentrations (.mu.g/ml) at steady state of 6.47 .+-. 1.51, a maximum steady-state concentration of 12.74 .+-. 1.60, and a minimum steady-state concentration of 1.43 .+-. 0.57, a dosage of 5 mg/kg every 8 h is recommended. Serum urea nitrogen, serum creatinine, and the fractional clearance of sodium sulfanilate were determined before and after GT treatment. Renal function remained within the base-base range during 7 days of GT administration.