PROLONGATION OF EPIDURAL-ANESTHESIA USING A LIPID DRUG CARRIER WITH PROCAINE, LIDOCAINE, AND TETRACAINE

This study evaluated the effect of a lipid drug carrier (iophendylate) on epidural anesthesia. The intensity and duration of motor blockade produced by aqueous and lipid preparations of local anesthetics were a ssessed in rabbits with long-term indwelling catheters in the epidural space. Motor blockades produced by procaine (1%, 2%, and 4%), lidocai ne (1%, 2%, and 4%), and tetracaine (0.5%, 1%, and 2%) in normal salin e solution were compared with the effects produced by equimolar amount s of the drug solutions in iophendylate. Procaine (4%) in aqueous solu tion produced motor blockade lasting 30 +/-3.54 min (mean +/- SD) vers us 84 +/- 4.18 min in lipid solution. Lidocaine (2% and 4%) in aqueous solution produced motor blockade lasting 41 +/- 4.18 and 65 +/- 6.12 min versus 39 +/- 4.18 and 1.18 +/- 10.1 min, respectively, in lipid s olution. Aqueous tetracaine (0.5%, 1%, and 2%) produced motor blockade of 106 +/- 9.62, 189 +/- 6.52, and 273 +/- 26.8 min versus 284 +/- 14 .7, 335 +/- 15.8, and 365 +/- 26.9 min, respectively, in their lipid c ounterparts. A control group of animals that received normal saline so lution or iophendylate alone did not exhibit motor blockade. These res ults may be attributed to sustained release of local anesthetics from the lipid vehicle. Hence, lipid drug carriers may be effective in prol onging epidural anesthesia.