The long term objective of the proposed research is to develop a more effective drug delivery vehicle for percutaneous transport of medication.
The specific aims are: 1) to formulate pharmaceutically acceptable microemulsions, 2) solubilize lidocaine in the microemulsions, 3) characterize the physicochemical properties of microemulsions, 4) perform in vitro studies on lidocaine transport through excised hairless mouse skin, 5) conduct in vivo rat """"""""tail flick"""""""" test using microemulsions, macroemulsions and aqueous solutions containing lidocaine, 6) carry out skin irritation tests on laboratory animals. 7) compare absorption of lidocaine in microemulsion with lidocaine in aqueous solution in laboratory animals, and 8) carry out clinical tests on the bioavailability of lidocaine from microemulsions on human volunteers and correlate these results with those of aims 4) and 5). Major parts of the pilot studies for the first two specific aims have been completed. Further research is planned for characterization of the microemulsion structure by measuring such properties as electrical conductivity, viscosity, and quasielastic light scattering. Experiments have been designed with the assistance of a biostatistician to make significant conclusions on the effect of vehicle structure (e.g. microemulsion, macroemulsion and aqueous solution) on the bioavailability of lidocaine. Diffusion of lidocaine through excised mouse skin will be carried out from different vehicles to correlate quantitatively the flux of lidocaine with the results of the rat """"""""tail flick"""""""" test and human volunteer responses. This research has a potential for producing an effective topical anesthetic vehicle which will provide relief to patients who must submit to many painful procedures such as phlebotomy, bone marrow biopsy and lumbar punctures. If microemulsions increase the absorption of topically applied lidocaine, then such vehicles can be employed to topical applications of cardiac drugs, steroids and analgesics.
