Effects of octreotide and morphine on the clearance rate of indium-111-pentetreotide from the epidural space

In this study we aimed to evaluate the possible mechanisms by which somatos tatin acts when given epidurally. Twenty male New Zealand rabbits were rand omly separated into four groups and various drugs were administered via a c audal epidural catheter. Group 1 received a bolus of 3.7 MBq indium-111 (In -111)-pentetreotide, group 2 received 200 mu g octreotide and after 15 min a bolus of 3.7 MBq In-111-pentetreotide, group 3 received 0.1 mg morphine a nd after 15 min a bolus of 3.7 MBq In-111-pentetreotide, and group 4 receiv ed a bolus of 3.7 MBq technetium-99m (Tc-99(m))-diethylene triamine pentaac etic acid (DTPA). Dynamic images of 60 min' duration were obtained from the posterior projection. T-1/2 fast and T-1/2 total clearance half-times were calculated. When unlabelled octreotide was given to block somatostatin rec eptors, clearance of In-111-pentetreotide was found to be faster. Epidural morphine administration did not change the clearance rate of In-111-pentetr eotide. All these findings are in favour of octreotide binding to its proba ble own specific receptors present in the epidural space. ((C) 2000 Lippinc ott William & Wilkins).