Comparison of absorption of aqueous lidocaine and liposome lidocaine following topical application on rabbit vessels.

Liposomes are small particles that encapsulate lidocaine to form topical drug carriers. Forty rabbits were used to compare the absorption of aqueous lidocaine with that of liposome lidocaine after application of each on femoral and iliac vessels. Both agents entered the circulation rapidly. The serum levels of lidocaine were significantly lower and the peaks in concentration appeared later after the use of liposome lidocaine than after the use of aqueous lidocaine. This phenomenon was due to local accumulation of liposome lidocaine and slow release of lidocaine from the liposome. As a topical spasmolytic agent, liposome lidocaine may be superior to the aqueous form due to a lower serum concentration and less total absorption.