Antinociceptive activity of Δ9-tetrahydrocannabinol non-ionic microemulsions

Δ9-Tetrahydrocannabinol (Δ9-THC), the major psychoactive constituent of Cannabis sativa L., has been widely studied for its potential pharmaceutical application in the treatment of various diseases and disturbs. This sparingly soluble terpeno-phenolic compound is not easy to handle and to be formulated in pharmaceutical preparations.The aim of this work was to develop a stable aqueous Δ9-THC formulation acceptable for different ways of administration, and to evaluate the therapeutic properties of the new Δ9-THC based preparation for pain treatment. Due to the thermodynamic stability and advantages of microemulsion based systems, the study was focused on the identification of aqueous microemulsion based systems containing Δ9-THC.Oil in water Δ9-THC microemulsions were individuated through phase diagrams construction, using the non-ionic surfactant Solutol®HS15, being this surfactant acceptable for parenteral administration in human. A selected microemulsion samples containing 0.2wt% of Δ9-THC, stable up to 52°C, was successfully assayed on animal models of pain. Significant antinociceptive activity has been detected by both intraperitoneal and intragastric administration of the new Δ9-THC pharmaceutical preparation. The effect has been highlighted in shorter time if compared to a preparation of the same active principle based on previously reported conventional preparation. © 2010 Elsevier B.V.