[Epidural administration of bupivacaine in glycerine solution can prolong analgesia]

Glycerine has long been used with phenol as a drug depot in control of intractable pain. However, through our literature review, glycerine has never been used to prolong the pharmacological effects of a local anesthetic, such as bupivacaine. Our study is an attempt to use the same mechanism to further extend the pharmacologic effects of a popular long lasting anesthetic in a commonly used technique. Fifteen adult patients with cancer pain received 0.125% bupivacaine via a chronically implanted epidural catheter. In a blind study of pain control: Group I, consisting of 8 patients, received 5 ml 0.125% bupivacaine in normal saline; group II, consisting of 7 patients, received the same amount of the same strength anesthetic dissolved in 50% glycerine. The pharmacological effect was assessed by evaluation of intensity and duration of sensory as well as motor blockade. Our preliminary experimental experience revealed that significant prolongation (11.8 +/- 2.3 h vs 7.6 +/- 1.8 h, p less than 0.01) of analgesia was observed with the glycerine solution as compared to the saline solution. There was no motor blockade or other adverse effects or complications. This markedly prolonged analgesic effect is attributed to the slow release of the local anesthetic agent from the glycerine base which functions as a drug depot. Other clinical applications of this novel approach in pain relief are currently under investigation.