Executive Summary

CHYMOPAPAIN LABELING REVISIONS FOLLOWING REPORTS OF PARAPLEGIA are under discussion at a meeting o fits Radiopharmaceutical Drugs advisory cmte. May 18. Surgical-Dental Div. Deputy Director Philip Walters stated that since the drug was approved in November 1982, there have been four cases of transverse myelitis/myelopathy reported in patients w ho have undergone chymopapain treatment. Three cases have resulted in paraplegia and one case has partially recovered paraplegia with paraparesis. Walther noted that "the mfr. of chymopapain has asked for a labeling change." Smith Labs, which market Chymodiactin, said it initially reported the adverse reactions to FDA. Baxter Travenol recently entered the market with the January Approval of Discase. Current labeling for Chymodiactin notes under the adverse reactions section: "Transverse myelitis has occurred in one patient but a causal relationship to the drug has not been established because the onset of the event occurred approximately 21 days after chemonucleolysis." The four case reported to FDA had a delay of onset of 2-3 weeks without prior problems. FDAer Martin Nissel, MD, noted that among an estimated 72,000 chymopapain injections there have been 27 severe neurological reactions. He explained that the cases of transverse myelitis/myelopathy probably were associated with "extravasations of the radiocontrast material" and its entrance into the subarachnoid space during discography. The adverse reactions were brought before the radiopharmaceutical cmte. because of the involvement of contrast agents. Commenting on the advisory cmte. meeting, Smith Labs told "The Pink Sheet" it does not believe the cases of transverse myelitis were caused by the same mechanism as the other neurological problems. The company said the incidence of paraplegia was delayed two to three weeks whereas other neurological problem -- several of which have been associated with the mixture of chymopapain and media contrast in the intrathecal space -- showed up within several hours. Smith Labs VP-clinical development Karl Agre reported the results of a recent baboon study the company undertook. He said the study suggests that if chymopapain and contrast media are in combination and get into the spinal fluid "they create a lot more neuorotoxicity than either one can do alone." Agre added that "a secondary concern" is that the agents approved for discography appear to the most toxic, whereas those not approved appear "somewhat less toxic." Squibb's Renografin and Sterling's Hypaque contrast media are approved for discography. Mallinckrodt's Conray has also been used with chymopapain. Smith Labs found no significant difference between the use of chymopapain in combination with either ionic or nonionic agents. Cmte. chairman Barry Siegel, MD, Washington University School of Medicine, questioned whether studies on a larger group of animals and additional post-marketing clinical data "might lead one to believe that nonionic agents are really the way to go if the animal data suggest there really is a lesser frequency of combined adverse effects with the nonionic agents." The cmte. concluded, however, that it lacked expertise to make any recommendation to the agency regarding chymopapain adverse reactions.