In vivo approach to determine the route of optimal drug absorption in rats.

The purpose of this paper is to describe the methodology to evaluate the optimal route of absorption in rats, avoiding the first pass effect of the liver (nasal, buccal and transdermal). These routes were investigated for a new benzamide, for which an absorption profile close to the intramuscular route is desired. Nasal route was investigated on anaesthetized rats by perfusion at a feeble flow rate of a recirculated solution through a tube from a reservoir, to the posterior part of the nasal cavity.