Local Anesthetic Microencapsulation.
Annual rept. 1 Jun 82-28 Feb 83,
BIOTEK INC WOBURN MA
Pagination or Media Count:
Etidocaine-HCl-polymer core particles have been microencapsulated. Most of the product is in the anticipated 100-400 micron size range. Release rates vary from 50 release in one hour 75-105 micron, 10 coating to only about 40 release in one day 150-425 micron, 30 coating. Selected materials were evaluated for stability to various storage conditions and for bulk density and pore distribution. In vivo studies included determination of anesthesia of the peripheral nerves of guinea pigs. Circulating levels of anesthetics were measured after injection of solution and microcapsular suspensions in rabbits. Sciatic nerve blocks were short when using slow-releasing etidocaine-HCl microcapsules. However, when using a high concentration 8 drug of faster releasing microcapsules, many hours of nerve block were observed. Although the results were variable, individual blocks lasted as long as 2 and 4 days. Circulating levels of lidocaine were measured after I.M. injection of soluble and microencapsulated drug in rabbits. Almost no circulating lidocaine was found after injection of lidocaine base microcapsules. For lidocaine-HCl, the solution showed peak levels at 10 minutes of 5.6 microgramsml whereas for the same quantity of encapsulated drug the peak occurred at 1 hour and was only 0.9 microgramsml. Blood levels of CPK were also significantly lower when microencapsulated drug was injected. This is indicative of less local tissue damage.