Pharmacologic and toxicologic profile of chymopapain B (Chemolase).

The median lethal dose (LD50) of chymopapain B in mice was 82 mg/kg (22,000 units/kg) with 95% confidence limits of 75-90 mg/kg (20, 122-24, 146 units/kg) and in rats 92 (24,683 units/kg) with 95% confidence limits of 83-102 mg/kg (22,268-27, 366 units/kg). The mechanism of toxicity was hemorrhage due to destruction of the cement substance of the blood vessels. Intervertebral disc injection of chymopapain B in the rabbit at a dose level of 186 micrograms (50 units) caused chemonucleolysis in 67% of the rabbits as evidenced by partial dissolution of the nucleus pulposus. Chemonucleolysis was also noted at higher doses. No adverse affects were noted with a 20 fold increase to 3.7 mg (1000 units). A dose of 18.6 mg (5000 units)/disc caused paralysis of the hindlegs. A dose as high as 26.6 mg (7143 units) /disc caused nearly complete dissolution of the nucleus pulposus and can cause disruption of the annulus fibrosus and death. Guinea pigs receiving a sensitizing dose of 0.003 mg/kg (0.8 units/kg) chymopapain B intraperitoneally six times over two weeks were challenged with an intravenous dose of 0.03 mg (8 units)/kg. All animals exhibited marked anaphylactic signs with a resulting 50% fatality rate.