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UPDATE ON BST FDA approved Monsanto Company's recombinant bovine somatotropin (rbST) product, Posilac ® , in November 1993 after a comprehensive review of the product's safety and efficacy, including human food safety. Posilac ® is the only rbST product approved for increasing milk production in dairy cattle. The product has been commercially available since February 4, 1994. During the first year of commercial use of Posilac ® , a total of 806 reports of adverse effects were reported to Monsanto and submitted to FDA. The November/December 1995 issue of the FDA Veterinarian, included information on 509 reports of adverse effects reported in the next seven months from February 1 to August 25, 1995. The following is an update on the adverse experiences to Posilac ® reported to FDA from August 26, 1995 through February 3, 1996. During this period, FDA received 144 adverse experience reports (see table below.) It is important to note that a report of an adverse effect in relation to a drug does not itself establish that the effect was caused by the drug. FDA believes that 83 of the 144 reports were possibly associated with the use of Posilac ®, and that the other 61 reports were not related to treatment with Posilac ® . Also, all of the reported clinical manifestations are known to occur in dairy cattle not supplemented with Posilac ® . Of the 83 reports possibly related to the use of Posilac ® , 18 included reproductive disorders, 10 involved digestive disorders, 23 included mastitis, 19 included injection site reactions, 12 included swelling of the udder or abnormal milk, 9 included foot or leg problems, and 17 involved increased somatic cell counts. In some cases, a single report contained multiple conditions. The number and severity of the reported conditions raise no new animal health concerns about the safety of Posilac ® . There is no indication that the drug is any less effective than labeled. In addition, FDA and State regulatory officials have found no indication of a change in the incidence of violative drug residues in milk associated with the commercial use of Posilac ® . Based on the these reports of adverse reactions to Posilac ®, FDA finds no cause for concern. However, it is important for dairy farmers to continue to report all adverse reactions associated with the use of rbST. They may report such reactions to Monsanto, to FDA through their veterinarian, or directly to FDA's Center for Veterinary Medicine. CVM accepts collect calls during working hours, and an answering machine is available to record after-hours calls. The telephone numbers are (301) 594-1751 for collect calls during working hours, and (301) 594-0797 to leave a message on evenings and weekends.
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