Figure 28. Plots of the cumulative amounts ( £ U, y g) of buprenorphine (1)
excreted in urine against the area under the plasma concentration-time curve (AUC
t, yg.min/ml) at the time of urine collection in accordance with the equation
(30):
£ U = Cl
ren
[ AUCt AUCq ]
where AUCq is the area under the plasma concentration-time curve at x U = o. a)
For the 2.5632 mg/kg IV bolus dose of buprenorphine in dog B, Study #3, the
estimated renal clearance was 0.053 ml/min for the initial time period up to 271
min. b) Same as in (a), except the points up to 60 min were not included in the
regression (time; 90-363 min). Estimated renal clearance was 0.03 ml/min. This low
renal clearance could be attributable to the cessation of urinary excretion of
buprenorphine during the time interval between 180-240 min. c) In the same dog,
the estimated renal clearance was 0.86 ml/min for the latter time period between
1219-5650 min. d) For the 1.439 mg/kg IV bolus dose of buprenorphine in dog C,
Study #5, the estimated renal clearance was 0.51 ml/min for the initial time
period between 75-1164 min. In the same dog, regression according to the above
equation (30) gave the slope = Clren = 1.453 ml/min for the initial time period
up to 75 min. (Intercept = -12.6, r=0.997, see also Table 2).