PROLONGATION OF EPIDURAL BUPIVACAINE ANALGESIA WITH GLYCERIN

Glycerin has been wed as a drug carrier/depot, but never with local an aesthestics. This study was an attempt to use the slow drug release me chanism to prolong the anaesthetic effects of bupivacaine in epidural block. Twenty-seven adults with cancer pain were prospectively selecte d according to their primary lesions and problems, but their allocatio n to study groups was randomized. Group I (n = 13), received 5 ml bupi vacaine, 0.125% in normal saline via a previous implanted epidural cat heter. When the pain returned to its original intensity, the same amou nt of the same strength anaesthetic dissolved in 50% glycerin was give n via the same catheter Group II (n = 14) received the same solutions, but in the reverse order Also five patients in each group received pl ain 50% glycerin prior to administration of the anaesthetic solutions to serve as controls. The pharmacological effects were assessed by the blinded observers. Analgesia produced with glycerin solution was prol onged compared with the saline solution (12.2 vs 7.2 and 11.6 vs 7.4 h r, P < 0.01). The order of giving the solution did not produce any dif ferences. Plan 50% glycerin did not produce analgesic effects. Neither motor blockade nor other adverse effects or complications were observ ed in either group. It was concluded that 0.125% bupivacaine in 50% gl ycerin administered epidurally is not neurotoxic. The prolongation of analgesia observed is attributed to the slow release of bupivacaine fr om the glycerin base which functions as drug depot. In addition to rel ief of chronic pain, this novel approach may have other clinical appli cations such as the relief of labour or postoperative pain.