LONG-LASTING EPIDURAL SENSORY BLOCKADE BY NORMAL-BUTYL-PARA-AMINOBENZOATE IN THE TERMINALLY ILL INTRACTABLE CANCER PAIN PATIENT

An aqueous suspension of n-butyl-p-aminobenzoate (BAB), a highly lipid-soluble congener of benzocaine, was applied epidurally in terminally ill cancer patients with intractable pain. The suspension consisted of 10% BAB and 0.025% of the nonionic surfactant polysorbate 80 in 0.9% sodium chloride. Twelve consecutive patients received epidural BAB because pain was uncontrollable either by palliative radiotherapy or oral or epidural administrations of analgesics. The catheter or injecting needle was positioned at the segmental level of the pain. Repeated epidural injections were administered. In all patients, long-lasting sensory blockade (segmental analgesia) occurred, accompanied by a marked reduction or even absence of pain. In all patients, treatment with epidural opioids, alone or combined with local anesthetics, was no longer necessary. Five of the 12 patients did not require further administration of oral opioids. Motor, bowel, and bladder function were well preserved. In 6 patients, extensive necropsy of the spinal cord and spinal nerves did not reveal pathomorphologic changes. The outer aspect of the dura showed signs of focal necrosis on microscopy, yet its collage structure and thickness were unchanged. Epidurally, focal infiltrative reactions were seen. The epidural use of an extremely lipid-soluble-hence hydrophobic- local anesthetic, with an exceptionally low pKa (2.3), formulated in suspension of the base, is conceptually innovative and needs further investigation. The authors conclude that the epidural administration of a BAB suspension may bc an effective alternative to the neurolytic agents alcohol and phenol and may replace procedures such as cordotomy. Further investigation to determine the safety of BAB in this patient group appears warranted.