Study of blood metabolism and urinary excretion of chymopapain following intradiscal injection using a high-sensitivity enzyme immunoassay

To develop chymopapain-induced chemonucleolysis as an established treatment, it is necessary to determine the kinetics of chymopapain in blood and urine following intradiscal injection. To investigate the rate of blood metabolism and urinary excretion of chymopapain following intradiscal injection, we developed a high-sensitivity enzyme immunoassay for chymopapain. The sensitivity for this assay was lpg/tube (40amol). After injecting chymopapain into the nucleus pulposus of humans, levels of blood chymopapain were measured by enzyme immunoassay. The level of chymopapain in blood decreased gradually, with a half-life of 2-3 days. The half-life for urinary excretion was a little longer, at 3 days. It was also found that chymopapain in blood was not present as a free molecule but formed a complex that had a molecular weight of about 120 kDa. These findings suggest that most chymopapain would not have activity in blood.