Figure 56. Semilogarithmic plots of the amounts ( y g) buprenorphine
excreted in urine (a, b) and bile (c) per minute plotted against t-mid,
the mid point of the biological fluid collection interval, in accordance
with the reduced form of the equation (22):
Log aU/ At = (k'/2.303) t-mid + intercept
for a) 4.8 mg/kg IV infusion dose of buprenorphine in dog E (Study #9)
resulting in an estimated apparent rate constant of 0.0031/min
(half-life = 225 min); b) 4.6885 mg/kg IV infusion dose of buprenorphine
in dog B (Study #7) with an estimated apparent rate constant of
0.0157/min (half-life = 44.3 min); and c) dog E at the same above 4.8
mg/kg IV infusion dose of buprenorphine (Study #9), the biliary
excretion rate (ug/min) of buprenorphine could be fitted to a sum of two
exponentials resulting in apparent rate constants of 0.031/min
(half-life = 22.2 min) and 0.0028/min (half-life = 251 min)
respectively.